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Innovative Studless Enclosure System Could Revolutionize High-Performance Construction

Energy EfficiencyBuilding Science

For decades, the “perfect wall” has been recognized as an optimal path to robust, high-performance, moisture managed, and energy-efficient walls. Unfortunately, adoption by the home building industry has been slow due to labor challenges, higher initial construction costs and perceived complexity. In search of a better solution, the University of Minnesota NorthernSTAR Building America Team, in partnership with the U.S. Department of Energy and three affordable housing developers in Minneapolis and Denver, created a new and innovative studless building system. This innovative solid panel ‘”perfect wall” building and delivery system is more affordable and faster to build and, based on early results, produces a more efficient, robust, and resilient home.

Energy models for the studless panel house indicated approximately 40 percent energy savings over Minnesota code and 30 percent energy savings over Energy Star v3 assemblies. The performance and cost data from the first structures built is undergoing its initial review. Remarkably, the airtightness of the first Habitat for Humanity studless panel house was a 0.26 ACH@50. Additional preliminary data suggests total validation of the pioneering enclosure system with increased energy efficiency, durability and construction quality at the forefront. “The construction costs have been competitive and the performance has been outstanding,” said Patrick Huelman, project lead and Associate Extension Professor for the University of Minnesota. “There is a learning curve, but it is remarkably easy and short."

The group is excited about the future. Huelman shared that the University of Minnesota NorthernStar team “is currently doing extensive structural research at the Home Innovation Research Labs to optimize strength, improve constructability, and reduce costs for the Solid Panel Structure.” So far, this “solid panel” approach, with several variations, has been used on two dozen affordable homes in Minneapolis and St. Paul. Download the Overview of Solid Panel Structure (SPS) System [PDF] for step-by-step photos of the construction process.

For more information, installation videos and classroom training materials, visit the Solid Panel Structure page on the University of Minnesota website or contact Patrick Huelman.


Synthetic Stucco Without Failures

Building Science Photo 1

When applying a liquid waterproofing membrane over OSB or plywood sheathing, start by sealing the panel joints with a sandwich of fiberglass mesh and the liquid membrane. Mark Parlee

Photo 2

Mesh and sealant should be applied to all inside and outside corners. A brush can be used to work the membrane into tight spots. Mark Parlee

Photo 3

Here's another example of an outside corner being sealed with liquid membrane and mesh, followed by another layer of liquid membrane. Mark Parlee

Photo 4

Roof-to-wall intersections see an enormous amount of water, making these critical areas to flash well. Step flashing should be woven in with the roof shingles, and then a counterflashing installed to protect against water getting behind the top edge of the step flashing. Mark Parlee

Photo 5

At the roof's bottom edge, sidewall flashing must terminate with a kickout to deflect water away from the sidewall and into a gutter. Large, preformed kickouts are preferred for steep roofs. Mark Parlee

Photo 6

Shallow roofs don't require as big a kickout as steep ones do. Mark Parlee

Photo 7

Apply a layer of mesh and liquid WRB to the top edge of the step flashing (shown) and to the top of the counterflashing.  Mark Parlee

Photo 8

A cricket in the plane of the roof creates positive drainage away from the chimney. Use plenty of peel-and-stick on the cricket, lapping it onto the chimney and sealing its top edge with mesh and a liquid WRB. Mark Parlee

Photo 9

A liquid WRB can be sprayed on or rolled on. Spraying is faster, but rolling is easier to control. Mark Parlee

Photo 10

Through-wall flashing is needed at the transition from stucco to another type of siding, be it synthetic stone, vinyl, or fiber-cement. In this project, W.R. Grace Perm-A-Barrier wall membrane (the green membrane at the base of the wall) was used. The top edge of the through-flashing is adhered to the wall and sealed with mesh and liquid WRB. Mark Parlee

Photo 11

After the liquid WRB is applied, windows and doors are installed. Apply mesh and liquid WRB to the nail fins on the head and side jambs, but leave the sills open to allow water to drain out. Mark Parlee

Photo 12

Again, the sills are left open while the side and head jambs are pasted over with mesh and liquid WRB. Mark Parlee

Photo 13

The layer that most often gets missed in a DEFS assembly is the drainage layer. You can use a rainscreen material for this. Mark Parlee

Photo 14

The rainscreen forms a three-dimensional separation between the WRB and the base panels that will be installed over it.  Mark Parlee

Photo 15

The DEFS base panels, which replace the insulation panels of an EIFS assembly, are installed over the drainage layer.  Mark Parlee

Photo 16

Control joints are fashioned by spacing the base panels 1/2 inch apart ... Mark Parlee

Photo 17

... and by installing a vinyl strip that will accordion in and out as the wall swells and shrinks. Mark Parlee

Photo 18

Vertical control joints should completely divide the wall section. Bring the joint right through any transition at the wall base. Mark Parlee

Photo 19

Vertical control joints should completely divide the wall section. Bring the joint right through any transition at the wall base. Mark Parlee

Photo 20

Horizontal control joints are typically placed between floors along the second- (and third-) floor band joists. Mark Parlee

Photo 21

Where a horizontal joint intersects a roofline or bump-out, integrate the control joint with edge treatments at the base of a wall. Mark Parlee

Photo 22

A vinyl J-track, or casing bead, is installed at the base of the wall to receive the base panels. It has weep holes that allow water to drain out, and it functions as a screed when the stucco base coat is troweled on. Mark Parlee

Photo 23

Outside corners should get a corner bead to create a crisp edge to define architectural details in the facade. Mark Parlee

Photo 24

The base panel should finish out at least 2 inches above a paved surface or above a sloped roof. Mark Parlee

Photo 25

An EIFS system would typically include an impact-resistant mesh over the entire surface of the foam boards. With DEFS, mesh is applied only at the joints, to help prevent the panel edges from telegraphing through the stucco. The mesh is embedded in the base coat of stucco. Mark Parlee

Photo 26

Once the base coat has cured, foam trim is applied 3/8 inch away from the edge of windows and doors. Mark Parlee

Photo 27

The foam trim then gets a base coat. The channel between the foam trim and the window is later sealed with backer rod and caulk. Mark Parlee

Photo 28

When the backer rod and caulk are installed around the windows, the sealant needs to adhere to the backwrapped edge of the preformed foam trim, but not to the finish coat, to prevent contraction of the sealant from causing the finish coat to separate from the base coat. The tape securing the poly that protects the windows gives a crisp edge to apply the sealant to, free of any finish topping. Mark Parlee

Photo 29

The beveled transition to the stone base is built up with layers of EPS. Mark Parlee

Photo 30

The beveled EPS base will be covered with the stucco base coat. Mark Parlee

Photo 31

An acrylic latex is used to finish off the stucco. Mark Parlee

Photo 32

The finish coat can be sprayed on. Mark Parlee

Photo 33

After the latex acrylic is applied, it is worked with a trowel to achieve the desired texture and finish. Mark Parlee

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    I started out 38 years ago as a framing and siding contractor in Iowa and for the last 20 years, have worked as an exteriors contractor, doing complete exterior renovations and repairs. Over the years, the process of tearing off and replacing complete exteriors has revealed a multitude of poor details that have failed—experience that serves my consulting practice today.

    While I still keep a crew busy with exterior work, a big chunk of my business these days is providing forensic inspections and expert witness testimony for litigation throughout the Midwest. Right now we're seeing a rash of failures with all types of cladding materials, but especially with EIFS (exterior insulation finish systems) and DEFS (direct-applied exterior finish systems)—the predominant stucco assemblies used in this region—and with ACMV (adhered concrete masonry veneer) exteriors.

    I covered ACMV—which in essence is a variation on stucco—in JLC last year (see "Best Practices: Adhered Concrete Masonry Veneer," Oct/13). And JLC has covered EIFS several times in the past, including breaking the story by Richard Piper and Russell Kenney about the earliest EIFS failures soon after the system migrated to the U.S. from Europe ("EIFS Performance Review," Jun/92). Russell and Michael Kenney also wrote a piece in JLC ("Success with EIFS," Nov/01), which details a lot of the best practices that are still used today. These days, however, we have more options for drainage-plane materials, which I'll cover in this article. This time, I'm going to focus on DEFS, which are similar to EIFS, except that the two-part stucco finish is applied over a cementitious or special-OSB base instead of over EPS foam boards.

    As with EIFS, success with DEFS comes by providing an effective drainage assembly and taking care in detailing flashings and sealing joints. On nearly every job I look at that's in litigation, moisture is getting past the stucco face at critical junctures and is rotting out the framed wall. The damage caused is often extensive. On one recent project, three missing kickout flashings led to some $30,000 in repairs. In another case against a builder, water that was leaking through a single wire penetration sparked an $85,000 lawsuit.

    These are the kinds of numbers that you don't want to risk. Spending a couple extra bucks per square foot to get the right materials and exterior details can be viewed as a savings, not an added cost, when compared with being involved in litigation down the road. Don't mess around with low bids unless you're jonesing for a lawsuit or want to trash your reputation as a builder.


    I'm confident that the details shown here will work for any DEFS installation. To avoid liability, you need to compare them to the manufacturer's installation instructions and to the ICC-ES Evaluation Report. All the major manufacturers of synthetic stucco systems and the accessory products that are part of the exterior finish assembly have gone through the evaluation service process to get an Evaluation Services Report (ESR). Typically, these reports include language that states that whenever the established building code and the manufacturer's installation instructions or the ESR differ, the installation instructions or the ESR prevails. ESRs are available from the manufacturer or from the ICC Evaluation Service (icc-es.org).

    The main purpose of these documents is to assist code officials in determining what details are required to meet code, and some inspectors will require that you have copies of them, as well as copies of the installation instructions, on hand at the time of inspection. This doesn't happen a lot, but it's well within the building department's domain to insist on it. Certainly it's easy due-diligence to collect these reports and make them part of the job file. Take the time to familiarize yourself with ESRs (a guide to reading them can be found at icc-es.org/evaluation_reports/read.shtml). Knowing that you had them on file and that you checked your work against them will go a long way in a court of law if you're ever sued.


    The illustration above shows all the layers that make up an effective DEFS assembly. This assembly is built over structural sheathing. In theory, there are "approved" applications that allow you to install the base panels over open-stud framing (provided, of course, that the wall meets the wind-bracing requirements without sheathing).

    I don't consider a "direct-to-stud" application best practice. While possible in some perfect world, it's not likely to succeed in the real world. Between the time that the open framing gets covered with a weather-resistive barrier (WRB) and the rest of the cladding system is installed, too much can happen (such as just having the wind blow) to compromise this key waterproofing layer. Without backing behind it, the exposed building wrap is extremely vulnerable. Direct-to-stud applications are put out there to make the price of the finish system more attractive. After all, the base panel seems like sheathing and is certainly more substantial than EPS when compared with EIFS. But that doesn't mean the final assembly will endure.


    A more durable and fail-safe application is to use a liquid-applied waterproofing membrane over OSB or plywood sheathing. The first step to applying this membrane is to seal the panel joints with a "wet sandwich" of fiberglass mesh and the liquid membrane. We apply this around corners and all the way into the jambs of window and door openings, using a brush to work the liquid into tight corners and seams. Mesh and sealant should be applied to all inside and outside corners as well.

    The photos in this article show either StoGuard—a gold-colored liquid membrane—or Dryvit Backstop NT—a translucent blue material. Though not shown here, Parex produces WeatherTech WRB for its Armourwall stucco system, and BASF produces Senershield-R, the liquid WRB used with the Senergy finish system.

    There are a number of other liquid-applied membranes that could work, but be advised that the warranty provided by the stucco manufacturer won't apply unless you're using all the components of one system. I'm not a big believer in manufacturer warranties, as there are too many "outs" a manufacturer can take, but I do generally try to stick to the components of one system as much as is feasible.

    After the corners and seams have been sealed, the liquid membrane can be applied over the whole sheathing area by either rolling it or spraying it on.Spraying it on is a bit faster, but the over-spray can be messy. Rolling is much easier to control.


    Flashings get integrated at the WRB layer. Generally, they are applied to the sheathing after the WRB is applied, and then the top edge gets another layer of mesh embedded in more liquid membrane.

    Sidewall flashing. Roof-to-wall intersections typically see an enormous amount of water, making these critical areas to flash well. These must include step flashing that gets woven in with the roof shingles, and then a counterflashing to protect against water getting behind the top edge of the step flashing. At the bottom edge of the roof, sidewall flashing must terminate with a kickout to deflect the water away from the sidewall and into a gutter.

    For most builders this is not news, and we're seeing step flashing and kickouts installed more and more. The big problem is that the kickout is usually undersized. The gush of water that comes racing down the roof hits the undersized kickout and simply spills over the edge, soaking the wall below and eventually finding its way into the cladding. To avoid this, we use large, preformed kickouts, like those made by DryFlekt, on steep roofs. Shallower roofs don't require as big a kickout.

    The top edge of the step flashing gets a layer of mesh and liquid WRB, as does the top edge of the counterflashing. The beauty of a liquid WRB is that each flashing layer can be made an integral part of the WRB.

    Chimney flashing. Just like sidewalls, the roof-chimney intersection sees a lot of water. The first step is to make sure that there's a cricket formed into the plane of the roof to create positive drainage away from the chimney. We always use plenty of peel-and-stick on the cricket, lapping it onto the chimney, and (you guessed it) sealing the top edge of this with mesh and liquid WRB. (Hopefully you're seeing a theme emerging here.)

    Siding transitions. Residential exteriors often combine stucco with another cladding. In our area we see a lot of transitions from stucco and synthetic stone, as well as from stucco to a horizontal siding, be it vinyl or fiber-cement. Any of these transitions needs through-wall flashing. We may use a W.R. Grace membrane, such as Perm-A-Barrier wall membrane (the green membrane at the base of the wall in photos 9 and 10). Again, the top edge of this through-flashing adheres to the wall and is sealed with mesh and liquid WRB.

    Wall penetrations. Wiring conduit, plumbing, pipes, exhaust vents, AC linesets, and all other wall penetrations have to be flashed. Flashing panels, such as those made by Quickflash Weatherproofing Products, are our go-to product for sealing these areas. And, like all the other flashing, these get sealed in with mesh tape and liquid WRB.

    Windows and doors. These should be installed after the liquid WRB has been applied. As noted earlier, the entire rough opening gets treated first. After the unit goes in, the nail fins along the head and side jambs get pasted over with mesh and liquid WRB. But the sills are left open so water that might leak through the window or door has a way to drain out.

    An L-flashing is required by code along the head. We typically use colored metal bent with a 4-inch back leg, and a 2-inch front leg with a 45-degree downturn along the front edge. This can be applied right over the top nail fin and pasted in with mesh and liquid WRB.


    The layer that most often gets missed in a DEFS assembly is the drainage layer. I typically use a rainscreen material, such as Keene Building Products' Driwall Rainscreen or Benjamin-Obdyke's Home Slicker, the bright yellow matrix that's shown in the photos in this article. I've also used Masonry Technology's Gravity Cavity, which was developed for brick walls but works for stucco systems as well. You could even use a vertically grooved building wrap, such as Tyvek StuccoWrap.

    The key is to use a material that creates a three-dimensional separation between the WRB and the base panels that will be installed over it. The liquid-applied WRBs are somewhat permeable, and if the base panel is pressed tight against them, any water that gets behind the base panel has the potential to wick through the WRB. The separation created by the drainage matrix allows the water to drain down the wall instead.


    Over the drainage matrix go the base panels. This is the key difference between EIFS and DEFS assemblies. The DEFS base panel replaces the insulation panel found in an EIFS assembly. The assembly loses its insulation value, but it gains in durability and impact resistance.

    There are a number of options for stucco base panels that can be used. We typically use PermaBase, a cementitious panel made by National Gypsum. We also see a lot of James Hardie HardieBacker fiber-cement panels and LP SmartSide, an OSB product that's treated with a zinc borate compound to discourage fungal growth.

    Control joints. As with an EIFS assembly, the wall area needs to be segmented by placing a control joint every 10 to 12 feet, both vertically and horizontally. The purpose of these joints is to force controlled cracks. If the wall area were larger, the stucco coating would pull itself apart due to thermal expansion and the wood framing's swelling and shrinking due to changes in humidity. By installing a control joint, however, you limit the cumulative expansion over the wall area, essentially breaking the wall into a neat matrix of rectangles.

    The control joint is fashioned by spacing the base panels 1/2 inch apart and applying a vinyl strip with an "M" profile that will accordion in and out as the wall swells and shrinks. Vinyl stucco accessories, including control joint strips and corner bead, are available from a number of sources; one common supplier is AMICO Building Products.

    Vertical control joints should completely divide the wall section. We bring the joint right through any transition at the wall base. Horizontal control joints are typically placed between floors along the second- (and third-) floor band joists. Where the horizontal joint intersects a roofline or bump-out, we are careful to integrate the control joint with edge treatments at the base of a wall.

    J-track and corner bead. We typically use a vinyl J-track (sometimes sold as "casing bead") at the base of walls to finish out the exposed bottom edges of the panels. True to its name, it has a J-profile to receive base panel, and it has weep holes that will allow any water that drains through the assembly to escape. It functions like a screed as well. When the stucco base coat is troweled on, the installer's trowel will ride on the proud, outside edge, revealing a small slice of vinyl that will later be painted over by the finish coat.

    Outside corners should get a corner bead to create a crisp edge to define architectural details in the facade.

    The base panel should finish out at least 2 inches above a paved surface or above a sloped roof. Above exposed grade, most manufacturers will allow a minimum of 6 inches, which conforms with the 2009 IRC, but better is the old code standard of 8 inches, to keep the bottom of the stucco out of the splash zone at the dripline.


    An EIFS system would typically include an impact-resistant mesh over the entire surface of the foam boards. With DEFS, mesh is applied only at the joints, to help prevent the panel edges from telegraphing through the stucco. Like the mesh applied at the WRB layer, the mesh applied to the joints at the base panel layer is embedded—only in this case the embedding material is the stucco base coat.

    This base coat is a cementitious material. It's not quite as hard as the scratch coat in a traditional three-coat system, and it doesn't go on as thick. Each manufacturer provides specifications for the thickness, typically around 3/8 inch to 1/2 inch per coat. What's critical is that the material be applied at a consistent thickness, so there are no sags or recesses. Much like with a plastered interior wall, imperfections in the base coat will telegraph through the finish coat.


    As mentioned earlier, the detailing of windows and doors starts at the WRB layer. After the base coat has cured, we apply a foam trim and give that a base coat. The trim is held 3/8 inch away from the edge of the window or door, creating a channel that will later be sealed with backer rod and caulk, as shown in the illustration above.

    For the trim, we use a pre-formed foam trim. This is sold either as pre-finished trim or as a starter strip for EIFS foam board with a "backwrapped" edge. This ensures that the edge and back are coated with an even base coat that will keep water from being absorbed into the EPS trim, and it provides a uniform surface for the caulk sealant, which is applied as a final step after the finish coat. When we finally do apply the backer rod and caulk around the windows, we want the sealant to adhere to the backwrapped edge, not to the finish coat. The thinking here is that the contraction of the sealant, which tugs at the ends of its hourglass profile, could cause the finish coat to separate from the base coat. To prevent this from happening, we are careful to tape the windows so that the edge of the tape securing the poly that protects the windows will give us a crisp edge to which we can apply our sealant, free of any finish topping.

    Along with applying window and door trim, we now can finish the detailing of the transition to the stone base—a common detail in our area. The beveled base was built up with layers of EPS and finished over with the stucco base coat.


    The finish coat is an acrylic latex. We refer to it as "thickened paint." These days it's a pretty good elastomeric material. And manufacturers continue to improve the formulation. It can be sprayed on, but afterward should be worked to the proper texture with trowels. The guys who do this work are amazingly skilled with a trowel and can create a wide variety of finishes.


    The final step, as noted, is applying sealant at windows and doors, per the illustration. The head should not be caulked, so that any water that leaks behind the stucco and drips down the drainage matrix will have a way to escape. Similarly, the sill should be left open so that any water that leaks through the windows can flow into the drainage cavity in the assembly and out the bottom edge.

    These details will work to keep water out of the walls. But remember, check them against the manufacturer's installation instructions and the product ESR. And document all your work. If problems arise down the road, you want to be able to establish the fact that you adhered to the manufacturer's guidelines at every step.


    Best Practices: Adhered Concrete Masonry Veneer

    Energy EfficiencyBuilding Science
  • --> Photo 1

    At the exterior steps on the house, we had to install aluminum flashing first to bridge over the sheathing transition. Mark Parlee

    Photo 2

    After installing the weep screed, we cover the walls with housewrap and building paper ... Mark Parlee

    Photo 3

    ... and finally, install the rainscreen material. Mark Parlee

    Photo 4

    Lath and the scratch coat will go over the rainscreen mat, followed by mortar and stone. Mark Parlee

    Photo 5

    When we first inspected this house, most of the edges where uncovered and showing a lot of corrosion. Mark Parlee

    Photo 6

    On this particular house, we found some attempt to install kick-out flashing above the gutters on roofs intersecting sidewalls. The kick-out shown had probably been installed after-the-fact, and it was much too little, much too late. Mark Parlee

    Photo 7

    You can see clearly the tragic result of having such a wimpy kick-out flashing.

    Photo 8

    To do it right, we used a pre-formed kick-out flashing by DryFlekt at the base of the run.

    Photo 9

    The weep screed was followed by housewrap, black paper, rainscreen mat, and lath, all terminating to a weep screed at the roofline before applying the scratch coat.

    Photo 10

    Note the small cricket at the end of the valley above the kick-out. This is a variant of the kick-out and it performs the same critical task of diverting water away from the walls.

    Photo 11

    Around windows and doors, care needs to be taken to integrate flashing tape and housewrap. On the sides and bottom, the flashing should lap over the housewrap; but at the head, the housewrap should lap over the flashing.

    Photo 12

    At the head we install a weep screed, followed by metal lath.

    Photo 13

    Along window jambs and sills we install metal casing bead, spaced about 3/8-inch from the window flange.

    Photo 14

    After the stone gets installed, the gaps formed by the casing bead (14) will be filled with backer rod ...

    Photo 15

    ... and (after taping off the windows with blue painter's tape) finished with a bead of sealant.

    Photo 16

    When we peel off the blue tape, we get a joint with crisp edges. Clayton

    Photo 17

    Nothing special has to happen where stone wraps around an inside wall corner. It is the same materials on each face of the wall, and there's no reason for them to move at dissimilar rates. But on the inside corner,one wall will get stone and the other has EIFS.

    Photo 18

    Ordinarily we would wrap the inside corner with housewrap (being careful to avoid having a joint), but in this repair we took extra care to ensure that no water got behind the housewrap by flashing the corner with tape and using a healthy portion of sealant, tooled over the tape, to create as good a barrier seal as we possibly could.

    Photo 19

    At the top of walls, we can bring the rainscreen mat right to the J-bead supporting the soffit.

    Photo 20

    A rake return, like the ones on the gable ends of this house, is a different animal. Here we have a vertical joint that will see its fair share of wind and rain.

    Photo 21

    Along the small section of roof above a rake return, we need a weep screed above the shingles.

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    Most of my work is in exterior remediation, both as a builder specializing in exterior work and (more and more these days) as a building consultant inspecting and advising owners and builders when moisture problems arise. I see a lot of failures, and most of the hands-on work we do is fixing other builders' mistakes. Daily I am reminded of the need for wider understanding of best practices, and that is especially true with adhered concrete masonry veneer (ACMV). We call this material "stone," but we all know that it is a non-load-bearing concrete cladding made to look like pieces of stone set in mortar that is bonded to a stucco scratch coat. We really need to be treating this material like stucco with chunks of concrete in it. When we lose sight of that, problems arise.

    ACMV has been increasing in popularity as a cladding on mid-range and high-end homes for the last decade, and across the Midwest where I work, a huge number of these homes are now showing signs of water-damage because the ACMV wasn't installed correctly the first time. I am an Exterior Design Institute (EDI) third-party EIFS and building envelope inspector, and this work has recently led me to work with relocation service companies. When a person is relocated by a company to a home with an EIFS exterior, it has for a long time been an automatic trigger for an inspection, owing to all the acute moisture problems—often leading to severe mold problems—suffered by buildings with EIFS. Now, at one of the three national companies I do inspections for, ACMV on the exterior of a home has become an automatic trigger for inspection, too. I believe that the problems are worse with ACMV, and they will make the EIFS problems look like a drop in the bucket.

    The best practices described in this article apply equally well to new construction, when they should always be used, as well as to remediation. But if you apply them in new construction, you won't have to apply them as a repair.

    I've written a number of articles for about both ACMV and EIFS failures. In this article, I'm going to focus on doing it right the first time. But the photos come from a remediation job. It cost $33,000 to repair the problems on this 14-year-old home. Adding a drainage membrane from the outset would have cost only about a buck-and-a-half per square foot installed. That's pretty cheap insurance to keep the envelope dry and performing well, considering the alternatives.

    Drainable System

    If you get anything from this article, let it be this: ACMV must drain. This is true of any cladding system, but with ACMV it's especially important because all those chunks of concrete hold a lot of water. If that water can't drain, it's more likely to get sucked into the framed wall than it is to evaporate to the outside. Brick veneer works the same way, except that most builders know (and code demands) that there is a minimum 1-inch air space behind the veneer (although a 2-inch gap is recommended by the Brick Institute of America). While there can still be problems with this detail (namely from mortar droppings and squeeze-out that fills the space and creates numerous bridges for water to wick to the framing) for the most part the assembly works to allow moisture to drain to the outside from behind the brick. To create a drainable system, I always use a rainscreen material, such as Keene Driwall, which is shown in the photos for this job. Recently I have been using MTI Cavity Gravity, which was developed for brick walls but also works with EIFS and ACMV. It stays rigid, which makes applying the lath easier and helps to maintain an even thickness for the scratch coat.

    A rainscreen material makes the whole wall very forgiving, so you can get away with holes, thin spots in the scratch coat, and other mishaps in the assembly that are bound to occur no matter how diligent you are when inspecting the work. But what you can't skimp on is providing a place for the water to drain at the bottom. In fact, if you provide drainage but don't allow it to exit, you can accelerate the water damage because a build-up of water will concentrate at the base of the walls.

    To ensure good drainage at the base of walls, we always apply a weep screed. This is the essential piece that will allow drain water to exit the cladding assembly. At the exterior steps on the house, we had to install aluminum flashing first to bridge over the sheathing transition. This flashing extends down the wall into the drainable subgrade beneath the steps and sidewalk. This gave us a clean surface against which to adhere the sealant after installing backer rod in the gap between the concrete steps and the flashing.

    After installing the weep screed, we cover the walls with housewrap and building paper, and finally, install the rainscreen material. Lath and the scratch coat will go over the rainscreen mat, followed by mortar and stone.

    I get a lot of flak from builders about specifying both housewrap and black paper, but it doesn't cost that much more, especially if it prevents the high cost of a remediation. Without the rainscreen material, black paper would serve as an essential sacrificial layer over the housewrap, allowing water to drain between the two sheets. By itself, housewrap can form a capillary bond to mortar or when the two materials are pressed directly against each other. Either way, this can allow water to pass through the housewrap.

    With a rainscreen material, this is less of an issue, but I like having black paper to slow solar vapor drive. Because ACMV holds a lot of water, it is prone to evaporation toward the inside when the sun is beating down on a wet wall. Housewraps are made to be permeable to promote drying, but that means moisture vapor can pass through them from outside to inside. The black paper will not prevent solar vapor drive, but it will slow it down. If we can slow down the wetting time, we have a better chance of avoiding problems.

    Stucco Basics

    In addition to always applying a weep screed, there are a few other basic rules for stucco that apply to ACMV.

    Lath. Metal lath must be installed with the right side up, or the scratch coat will slide off the building. On wood framing, lath must be installed with the long dimension perpendicular to studs. At corners, make sure that the lath is not installed too tightly, or the scratch will pop off. Best practice calls for securing lath with furring nails, which place the lath roughly in the center of the scratch coat. But when securing lath over a rainscreen, staples work well, too. Just turn down the pressure so you don't compress the mat too much.

    Scratch coat. Clean sand is the key to creating a strong scratch coat. Dirty sand, or sand intentionally mixed with clay to improve workability, will become porous as the clay dissolves, leaving behind air pockets. The mix for a scratch coat should be rich (high cement content) so that it cures hard. Perform a "nail test" on cured scratch coat: If dragging a nail across the surface leaves a white line, it is hard enough to apply the mortar that adheres the stone cladding.

    Ideally, the scratch coat must cover the lath. As mentioned, this doesn't always happen in the field, but it is important that this happen at the edges, otherwise the lath will rust. When we first inspected this house, most of the edges where uncovered and showing a lot of corrosion.

    Solid, dry structure. Stucco can't tolerate a lot of movement and is prone to cracking. To minimize cracking, walls must be rigid. Sound framing, with particular attention paid to wind bracing, applies (see "Bracing Walls for Wind," July/13). In addition, it's important to protect the structure from water during construction to avoid trapping moisture or soaking OSB sheathing, which can lead to swollen panel joints.

    Tim Healey

    Roof-Wall Intersections

    The intersection where a roof meets a wall turns out to be one of the most important details on the entire exterior. On this particular house, we found some attempt to install kick-out flashing above the gutters on roofs intersecting sidewalls. The kick-out shown had probably been installed after-the-fact, and it was much too little, much too late. You can see clearly the tragic result of having such a wimpy kick-out flashing.

    To do it right, we used a pre-formed kick-out flashing by DryFlekt at the base of the run. A steep roof, like the one shown in the photo, will require a sizable area to prevent spillover that would load the wall with water. The illustrations show in detail how this kick-out needs to be integrated with step flashing woven into the roof shingles.

    Over the step flashing, we completed our assembly, installing a weep screed along the slope of the roof. (Technically, you should hold the weep screed 2 inches above the shingles. But this detail looks strange, so we bring it right down to the roofline and have never had problems.) The weep screed was followed by housewrap, black paper, rainscreen mat, and lath, all terminating to a weep screed at the roofline before applying the scratch coat.

    Note the small cricket at the end of the valley above the kick-out. This is a variant of the kick-out and it performs the same critical task of diverting water away from the walls.

    We have to constantly remind ourselves that ACMV absorbs and holds a lot of water, so we need to do everything possible to avoid loading the stone with water. Wide overhangs and meticulous detailing on gutters and valleys are critically important.

    Windows and Doors

    Around windows and doors, care needs to be taken to integrate flashing tape and housewrap. On the sides and bottom, the flashing should lap over the housewrap; but at the head, the housewrap should lap over the flashing. If we had installed the windows to begin with, we would have installed a drainable sill pan that lapped over the top of the housewrap below the window. But on a remediation job, we have to work with the existing window installation. In this case, I am not too concerned that the sill is taped off, because the weep holes in the window frame drain to the outside of the tape where the rainscreen mat will be. I'd rather make sure that the water streaming off the glass and flowing over the sill doesn't seep into the wall along the top of the housewrap below the window. At the head we install a weep screed, followed by metal lath. Again, it's critical that water be allowed to drain, otherwise it can collect, eventually seeping inside. Along window jambs and sills we install metal casing bead, spaced about 3/8-inch from the window flange.

    After the stone gets installed, the gaps formed by the casing bead will be filled with backer rod and (after taping off the windows with blue painter's tape) finished with a bead of sealant. When we peel off the blue tape, we get a joint with crisp edges. Though I like this detail, I'm not too concerned about these joints around the opening because the whole assembly behind it is drainable. This also applies to the gaps in the scratch coat, which I'd rather not have. But I do like having the flexible joint between the window frame and the stone to accommodate the thermal expansion of dissimilar materials. What usually happens is that the masons will simply fill the gap between the window and the stone with mortar, and the mortar cracks almost immediately. If nothing else, this looks bad. But usually the wall is not drainable, so the crack also allows for the speedy flow of water into the wall.

    Inside corners

    Nothing special has to happen where stone wraps around an inside wall corner. It is the same materials on each face of the wall, and there's no reason for them to move at dissimilar rates. But on the inside corner, one wall will get stone and the other has EIFS.

    In this case we wanted a flexible joint to accommodate the potential for these two walls to move at different rates. We did this using the same detail we applied at the sides of window and door openings: installing a metal J-bead spaced about 3/8-inch from the corner. The gap then gets filled with backer rod and sealant before the stone is applied.

    On another section of the house, where a wimpy kick-out spilled over the wall, we had to replace the entire cladding assembly. Since the new stone we had did not replace the old stone, we created a detail that was consistent with some of the EIFS detailing on this house, using HardiePanel with a stucco finish (an affordable alternative to EIFS) installed over housewrap and rainscreen battens. This created an inside corner where the old stone met new HardiePanel. Ordinarily we would wrap the inside corner with housewrap (being careful to avoid having a joint), but in this repair we took extra care to ensure that no water got behind the housewrap by flashing the corner with tape and using a healthy portion of sealant, tooled over the tape, to create as good a barrier seal as we possibly could.

    Top of Wall

    At the top of walls, we can bring the rainscreen mat right to the J-bead supporting the soffit. Some experts would argue that the top edge should be finished off with a metal J-bead held away from the soffit and the gap sealed with backer rod and caulk. But I don't think this joint will ever see much water, even along the rake. If anything, the top of the rainscreen should be allowed to vent, which it will through the inevitable gaps in the scratch coat and around the vinyl soffit bead, which is never installed too tight.

    Rake Returns

    A rake return, like the ones on the gable ends of this house, is a different animal. Here we have a vertical joint that will see its fair share of wind and rain. We use the standard detail for any vertical joint, and just like the one used around windows and doors: We install a J-bead with a gap that we finish off with backer rod and sealant before the stone is applied. Along the small section of roof above a rake return, we need a weep screed above the shingles.

    By now you are probably getting a good idea of what works with ACMV: The assembly needs to be drainable using a rainscreen material over a well-detailed weather barrier. We believe in a two-layer weather resistive barrier to slow any vapor drive to the interior when you have a cladding material that stores a lot of water. All horizontal transitions need a weep screed to allow water to exit the assembly, and all vertical transitions between dissimilar materials need metal J-bead with a small gap so you can create a flexible joint by installing backer rod and sealant. If you follow these rules, you will have a fighting chance of avoiding expensive repairs.


    Masonry Through-Wall Flashing at Windows

    Energy EfficiencyBuilding Science

    Photo 1. Doug Horgan/BOWA

    As a high-end remodeling firm in the Washington, D.C., metro area, our company works on many homes that have brick and stone exteriors. We sub out most of the masonry work, and getting the details right sometimes requires careful supervision. We pay particular attention to through-wall flashing, especially at roofs and above and below windows. The through-wall flashing at the head and sill must be planned before the masons are even hired, and we have to be sure the masons follow our plans closely because getting the details wrong is a sure-fire path to water problems.

    That was the clear case on one recent job. Our work involved enclosing an open second-story deck above a kitchen. When scoping out the job, we learned that there was a leak: Water was coming through the recessed light in the soffit above the sink, which faced a large window. This window had previously been fixed by another contractor, and from the exterior it appeared to have a good weep system at the header. So, like everyone else, we assumed that the leak was in the roof and that enclosing the deck would solve the problem. But after we finished our work, the leak persisted. Whenever there was a long, windy rainstorm, water still dripped through the light.

    Photo 2. Doug Horgan/BOWA

    So we investigated more closely, starting with water-testing the wall above the window. After soaking the brick with a hose, sure enough, water began flowing through the light. Still, before launching into a multi-thousand-dollar masonry project, we inspected further by taking off the casing above the window. We could see that there was through-wall flashing at the header, but we could also see plenty of water getting around it.

    When we finally opened up the wall, we discovered that the through-wall flashing had been pieced in, with the seams simply lapped, not sealed. Water was draining off the housewrap and onto the head flashing, but it was leaking through the seams. Plus, there were no end dams, so water was spilling off each end of the flashing and finding its way past the housewrap, past a layer of foil-faced polyiso insulation, and into the wall.

    Photo 3. Doug Horgan/BOWA

    Above Openings

    To repair the problem, we opened up four courses in the wall—enough so that we could pull up the existing housewrap and install a one-piece, 18-inch-wide through-wall flashing. We typically try to use purpose-made rubberized asphalt "thru-wall" flashing materials. These are similar to the self-adhered flashings made for roofs or windows but have a stronger polyethylene face layer. The thicker material stands up to abrasion from masonry and tends to come in wider widths, so we can get a good lap behind the housewrap and still bring the flashing all the way out to the face of the brick.

    This last point is important because it prevents water from soaking back into the masonry below the flashing and finding its way into the framing. There are purpose-made flashing materials with metal drip edges, but they are expensive, difficult to work with, and aren't stocked in our area. On some jobs, we have fabricated stainless steel drips along the outer visible edge. Most of the time, however, we just have the masons bring the flexible through-wall flashing all the way out to the face of the brick.

    Photo 4. Doug Horgan/BOWA

    If you try to be clever and hide the edge of the material, know that holding it back any more than a tiny bit will allow water into the veneer. On existing work, we often find through-wall flashing cut back to the middle of the brick, which dumps water directly into the core of the brick and into the open back half of the head joints. Pulling the flashing all the way out to the face is a good way to ensure quality—and it isn't very noticeable once it's trimmed off.

    The other critical detail on any through-wall flashing is the end dam, which is simply a fold at each end of the flashing that brings the material up into a vertical head joint. This detail allows the flashing to function more like a collection channel, or spout, than a flat membrane. Creating an end dam is also more reliable than trying to seal overlapping pieces of flashing: Whenever we need a mid-span joint in flashing for a long run, we create end dams, turning the ends of each piece up into a head joint.

    Photo 5. Doug Horgan/BOWA

    Through-wall flashing needs to run longer than the jamb flashing on each side of the window, so water won't find its way back into the opening. To ensure that water can escape, weep holes should be placed at each end dam and at every third brick to provide ample drainage. Weeps are commonly created by open head joints, or by fitting head joints with cotton rope purpose-made plastic devices (although tubes tend to clog or become insect nests), or drainable mesh (visible at the bottom of the wall in photo 7).

    On this house we also reworked the window wrap and casing, and added an aluminum head flashing. By pushing most of the water through the masonry and protecting against wind-blown and incidental moisture, we were able to stop the persistent leak.

    Photo 6. Doug Horgan/BOWA

    Below Openings

    We are careful to flash around windows, using high-quality butyl-rubber flashing and properly integrating it with the housewrap and window flashing. (For examples of details using a variety of different flashing materials, see "Flashing a Flanged Window," Nov/12, and "Flashing and Trimming a Window," Aug/12.)

    A key feature of a good window flashing is a drainable sill pan, which gathers the water leaking around a window unit and directs it to the outside. We find that a lot of masons, if left to their own devices, will let the sill pan drain into the air space behind the brick, leaving the through-wall flashing at the base of the wall to do all the work. However, we feel that best-practice should include a through-wall flashing right below each window that is integrated with the sill pan. Any water leaking from any window needs a clear path out of the wall as quickly as possible.

    Photo 7. Doug Horgan/BOWA

    It's important to run the through-wall flashing long enough so that the jamb flashing, as well as the sill pan, lap over it. This includes the jamb flashing between windows. (Make sure to lap correctly; reverse shingling is the bane of every flashing job.) And as with every through-wall flashing, each end must be turned up to create an end dam so that water is channeled out of the wall. Otherwise, it is likely to dribble back into the masonry and find its way inside.


    Why Wall Flashing Installation Errors Are So Common

    Energy EfficiencyBuilding Science

    As Christine Williamson (the architect behind Instagram's Buildingsciencefightclub) explains in a recent IG post, lots of builders confuse the cladding of a building with the building's water control layer, and, she surmises, this is the reason for a very common omission: Not installing through-wall flashing, the (usually) L-shaped piece of metal above an opening or at the base of a wall.

    In her post (embedded below), Ms. Williamson aptly notes that installing through-wall flashing and allowing water to drain out is a much more reliable approach to protecting a wall from water damage than trying to prevent water from entering in the first place. As she says it: "You will never be perfect at keeping 100% of water out of the wall - in providing drainage, you don’t have to be. This isn’t a compromise position that 'accepts' poor craftsmanship, it’s just smart design."

    View this post on Instagram                  

    One of my favorite walking routes takes me past a lot of garages... nearly all of them poorly flashed. This is such a frustrating construction defect because it’s so common and yet so inexpensive to avoid: simply provide an outlet for the water that gets behind the cladding to drain safely to the exterior. Usually this is in the form of “through wall flashing,” which is a more or less L-shaped piece of metal (made of stainless steel, copper, lead coated copper, or even painted aluminum) that directs water from the face of the water control layer (the code term is “WRB” or water resistive barrier) to the exterior. * It’s really important that when through wall flashing is included, it’s not caulked or sealed to the cladding. The whole point is to let water out! This can be tough to accept intuitively, but I promise providing drainage is much, much more important than blocking entry. You will never be perfect at keeping 100% of water out of the wall — in providing drainage, you don’t have to be. This isn’t a compromise position that “accepts” poor craftsmanship, it’s just smart design. * Sketched with #Morpholiotrace * #architecture #architecturestudent #architecturestudio #architecturaldetail #architecturedetail #designdetail #womeninarchitecture #womeninconstruction #sustainablearchitecture #constructiondetail #buildingscience #buildingsciencefightclub

    A post shared by Christine Williamson (@buildingsciencefightclub) on Aug 15, 2020 at 4:29am PDT

    Be sure to click on all the slides in the post above to understand the scope of the problems and Ms. Williamson's guidance on solving them.

    It's surprising to us here at JLC that this omission continues to be so prevalent after all the attention we have brought to it over the years, but we agree with Ms. Williamson that it remains incredibly common.

    One solution that works on cantilevered areas is to build a drainable reveal. Click to enlarge.

    Stucco buckets. One distinct and especially thorny problem Ms. Williamson points out is a problem we earlier dubbed "stucco buckets" - overhangs where stucco wraps from the vertical wall to the horizontal surface without anywhere for liquid water to drain out (see "Avoiding Stucco Buckets"; Nov/18).

    One solution is a drainable reveal, with variations that work for stucco (shown left), as well as thin brick. Another option described in "Avoiding Stucco Buckets" is to divert the water with a channel that drains the water away from the bucket (the closed cladding above an opening).

    As Ms. Williamson notes, the omission of through-wall flashing is especially common with stucco, but it's not the only cladding that gets short-changed. Providing an escape route for water is vitally important for all cladding.

    Here are some good resources for detailing through-wall flashing in a variety of cladding types:


    16 States' Attorneys General Concerned About Energy Efficiency Standards

    Energy Efficiency

    Editor's Note: Sixteen States' Attourneys General signed on to a letter to the U.S. Department of Energy outlining the deadlines it has failed to comply with regarding energy efficiency standard review mandated by the Energy Policy and Conservation Act.Click here to view the letter (PDF).


    Air Sealing Whys and Hows

    Energy Efficiency

    Duct boots should be carefully sealed using foam sealant. Steve Easley

    In my work as a home building consultant, I often find myself training builders and crews about the importance of airtight construction. The new energy code mandates blower-door verification for homes, with a maximum 3 ACH50 in climate zones 3 to 8. If you fail the test, you’ll have to call your crews back in to air-seal as a retrofit. Three ACH50 is a tough mark for some builders to get to from the previous requirement of 7 ACH50. But there are good reasons for builders to focus on airtightness.

    As much as a third of a home’s heating and cooling bills can be traced to air infiltration and exfiltration. So tightening up a house is an important step in energy efficiency. But that’s not the only reason airtightness matters. In addition, air leaks bring warm, humid air into contact with cold surfaces. That creates conditions ripe for mold growth and decay. And of course, drafts in homes are a comfort issue that can lead to homeowner complaints. Some people mistakenly believe that air leaks help walls dry out, but it’s the opposite, as the leaking air is almost always warmer and wetter than the air it’s driven to. In my experience, the biggest cause of water-related damage in buildings is from water leaks from the outside, and the second is damage due to air leakage. Tighter is better as far as managing moisture to prevent rot and decay.

    Here, an air leak has led to condensation and severe moisture damage. Steve Easley

    Air leaks in the building shell can be costly and difficult to fix after the fact. But air-sealing a new home under construction should only take a few hours. Let’s look at the low-hanging fruit—the simple approaches that will help you hit 3 ACH50 the first time out.

    Attic First

    For an air leak to occur, you need to have a hole and a pressure difference. Pressure differences are caused by wind, stack pressure, and HVAC equipment. Yep, duct leakage creates pressure differences across the envelope that drive moisture, so seal and test your ducts.

    Fewer holes mean less leakage. Attics are particularly prone to losses from stack effect, which effectively turns a house into a drafting chimney (hence “chimney effect” is a synonym for “stack effect”). Air leaks at the top tend to be the most numerous and the easiest to remedy, making the attic the first place to focus on.

    I recently air-sealed a 3,300-square-foot house built in 1978 (a two-story over a crawlspace). Because the house had a family of bats in the attic, all the attic insulation had to be removed. This was a perfect opportunity to air-seal. By sealing only the attic leaks, we cut the whole house air leakage rate from 4,460 cfm to 2,180 cfm—more than half the total air leakage.

    Conscientiously air-sealing the attic ceiling after the drywall is hung—before insulation—makes getting to 3 ACH50 much easier. It doesn’t have to interrupt the sequence of the job, and it can be done with minimal cost. More production builders need to take this step.

    Partition wall plates are a big leak point at the attic floor plane. Drilled holes for wires make the problem worse. Steve Easley

    Here, the wall plate joint has been sealed with foam. Steve Easley

    An alternative to air-sealing from above is to seal the drywall to the plate. DuPont

    Wall Plates and Ceiling Drywall

    What does sealing the attic entail? It means identifying the big leak areas and addressing them. At the top of the list are wall plates. Partition and exterior walls are typically framed with truss chords fastened to the top plates. Once the ceilings are hung with drywall, you generally end up with hundreds of feet of cracks on either side of the top plates open to the attic. These can leak up .7 cfm per linear foot. Each stud bay in the partition effectively becomes a little chimney. Stack effect draws in air at the bottom of the wall plates and pushes it out the cracks into attics. Holes for electrical wiring, plumbing vents, and ductwork boots compound the leakage. One practical way to address this leak point is to send in a spray-foam contractor to hit just the leak areas (see “Air-Sealing the Lid,” JLC, August 2019).

    Can Lights

    Of all the openings in a house, one of the biggest from an air-leakage perspective is around recessed light fixtures. In one study, can lights accounted for an average of 9.1 CFM50, or about 0.15 to 0.31 ACH50, per fixture. Conventional recessed cans are so leaky, you can see right through them. Surprisingly, many so-called “airtight, IC-rated” fixtures (which is what the energy code requires) are not much better. One Owens Corning study found they leak .9 cfm per light.

    Better from an air-sealing perspective (and arguably from a lighting perspective, as well) are a range of new LED “can-less” fixtures that either have a low-profile housing or are surface mounted. Both types have simple plug-and-play-type wire connections that not only simplify the installation but result in almost no penetrations. (Consult the LED manufacturer for specific recommendations regarding insulation contact.)

    Recessed light fixtures are a major source of air leaks into attics. Here, light is shining up through the can light from below. Steve Easley

    Even IC-rated can lights like this unit may have significant leaks. Steve Easley

    Steve Easley

    Duct Terminations

    Duct boots at the end of HVAC supply runs through the attic are another big ceiling penetration from an air-sealing perspective. Carefully applying foam sealant to the perimeter of the boot and the drywall tends to be the easiest way to seal these leaks.

    Caulking the perimeter of the duct boot prevents air leakage. Steve Easley

    Knee Walls

    Knee-wall areas and the floor and roof sections outside attic trusses are protected from weather, but otherwise are “open” to outside. The best way to deal with these enormous leaks is with rigid foam or heavy cardboard sheathing (even building wraps can work). It is picky work to piece-in these sheet goods and foam or tape the edges. But if not done, the impact on performance can lead to costly warranty issues. (For more on this, see “Fixing the Bonus Room,” JLC, March 2017.)

    Sheet goods applied to the knee wall prevent a major air leak. Steve Easley

    Attached Garages

    Attics often have other huge openings that many builders don’t see as air leaks. A common one occurs in the ceilings of single-story attached garages where they bump up and connect to a larger attic space over the main house, or to a two-story wall. The best way to shut these huge leaks off is to apply sheathing or air-barrier material over them at the framing stage. Otherwise, you will need to go in later and cut pieces of rigid foam to block off the areas between the truss chords, and then seal the edges with foam sealant.

    The juncture between a garage roof and an attic space should be sheathed over before the trusses are set. Steve Easley


    Dropped ceilings above cabinets are often left open to the attic floor. The exterior wall gets insulated, and often the insulation contractor will lay a batt over the opening in the attic floor, but underneath that insulation is just one big hole to the unconditioned attic, which is effectively outside.

    The most effective way to seal these areas is by installing the ceiling drywall before framing out the soffits. A continuous drywall lid over the area effectively shuts down the airflow, whereas drywall that gets pieced on the sides and bottom of the soffits doesn’t. There are too many cracks at the soffit corners that corner bead and drywall mud don’t seal.

    Cabinet soffits represent a significant source of air leaks. Steve Easley

    Installing drywall at the soffit location before attaching the soffit creates an effective air seal. Steve Easley

    Not every builder can get the drywall contractor on board to hang the whole ceiling early in the schedule, but you may be able to get the pick-up framing crew to install a few selective sheets of drywall over the soffit area. It’s not much drywall compared with the entire ceiling. Having the pick-up crew install these few sheets may not be as disruptive as you might imagine.

    Bottom Plates and Band Joists

    Beyond the attic, there remains a host of wall air leaks on which builders can focus attention to produce a significant reduction in total leakage area. Plate-to-floor connections and band-joist areas are often poorly sealed. I’ve learned you need to seal both the sheathing-to-plate connection and the plate-to-floor connection.

    Sole plates should be sealed to the floor and to the sheathing. Steve Easley

    Sole plates at the base of walls are a significant leak point. Even the wall between the garage and the main house should be sealed at this location. Steve Easley

    The infrared camera captures this view of air leakage at the base of a wall during a blower-door test. Steve Easley

    Here, wind-washing has pushed cold air several feet up the inside face of an exterior wall. Steve Easley

    Band joists for second floors fall closer to the neutral pressure plane—the middle section of a building’s height—and therefore, they do not tend to be as affected by stack pressures. Nevertheless, they are still extremely leaky owing to the number of cracks formed by the pieces joining in this area.

    This cantilevered joist system is full of holes that would be troublesome to seal as a callback (see closeup, below). Steve Easley

    Steve Easley

    Some builders continue to believe that stuffing the rim with fiberglass is sufficient. Batts may work to insulate this area, but you first need to air-seal with caulk in the corners at the top and the bottom of the rim joists (the corner between the sill or wall plate and the top-side decking), as well as along the joists or floor trusses crossing the sill plate.

    This is awkward work, to say the least. Getting between the floor joists and the decking is difficult. Some framing crews have gotten skilled at handling a caulk gun as they frame, sealing the plates before installing floor decking, and then going back to apply one bead to seal the top of the rim to the deck. This is not the way every framing crew likes to work, however.

    Fiberglass insulation is ineffective at blocking air infiltration at the band joist (or anywhere else). Steve Easley

    This infrared image shows the ineffectiveness of fiberglass as an air seal. Steve Easley

    A much easier and still very effective way to address the rim joist is to seal the entire area with closed-cell spray foam. It can be cost-effectively foamed to a 1-inch thickness (or in colder areas, to 2 inches) and insulated with batts (flash-and-batt), or insulated to a great depth to satisfy the entire code-required wall R-value. Even if you’re not insulating the wall cavities with foam, insulating the rim joist entirely with closed-cell spray foam is turning out to be a go-to solution for an increasing number of builders.

    Spray foam makes an effective air seal at the band joist location. Steve Easley

    HVAC Penetrations

    Vents and ducts passing through framing can lead to some large, significant leaks through the building shell. Many HVAC ducts and vents run through boxed-out framing chases and connect an equipment room at slab level, or a basement or crawlspace, with the attic.

    This huge hidden hole will leak major amounts of air. Steve Easley


    There are two serious leaks that builders miss time and time again. One is the bathtub drain over crawlspaces. It’s not uncommon for plumbers to overcut the floor sheathing to make ample room to glue up the drain trap. This happens not only in wood-framed floors but also in slabs: Where the slab is formed to fit the trap gets left as a wide-open hole under the tub.

    Gaping holes are often left under tubs, allowing huge amounts of air infiltration from the crawlspace below. Steve Easley

    Here, the hole under the tub has been well sealed with rigid sheet material and gun foam. Steve Easley

    Holes in the slab that accommodate plumbing should also be filled and sealed. Steve Easley

    The other place that is missed is the wall behind the tub. Unlike most of the wall in the bathroom, which is air-sealed with drywall or backerboard, the area behind the tub, or tub platform, is often left open. The solution is simple: Before the tub surround is framed in or the tub installed hard to the framing, the wall needs to be covered with a panel stock. This is required by code.

    Here, the wall behind a tub has been insulated, but not air-sealed. Steve Easley

    Code requires air-sealing the area behind the tub, as shown here. Steve Easley

    Quality Assurance Key

    Inspection before the insulation is installed is critical to success and avoiding callbacks. Also inspect the outside just before cladding to make sure the air barrier is airtight and watertight.

    An inspection before insulation would have caught this big unsealed penetration. Steve Easley

    BFS and BMC Announce Planned $11.2B Merger

    Press ReleasesBusiness

    Editor’s Note: The press release below details today’ announcement that Builders FirstSource and BMC plan to merge into one large company serving most of the continental U.S. For further information, this investor presentation provides an excellent overview of what the combined company may look like. To learn more about the recent financial performance of these two companies, check out these summaries of BFS Q2 2020 earnings and BMC Q2 2020 earnings.

    Builders FirstSource, Inc. and BMC Stock Holdings, Inc., today announced that they have entered into a definitive merger agreement under which Builders FirstSource and BMC will combine in an all-stock merger transaction to create the nation’s premier supplier of building materials and services. The companies will host a joint conference call today at 7:30 a.m. Central Time (8:30 a.m. Eastern Time) to discuss the transaction.

    Under the terms of the agreement, which has been unanimously approved by the Boards of Directors of both companies, BMC shareholders will receive a fixed exchange ratio of 1.3125 shares of Builders FirstSource common stock for each share of BMC common stock. Upon completion of the merger, existing Builders FirstSource shareholders will own approximately 57% and existing BMC shareholders will own approximately 43% of the combined company on a fully diluted basis. The merger is expected to be tax free for U.S. federal income tax purposes.

    Click to enlarge.

    After a 90-day transition period following the completion of the merger, Chad Crow, current Chief Executive Officer of Builders FirstSource, will retire as previously announced and will be succeeded as Chief Executive Officer of the combined company by Dave Flitman, current Chief Executive Officer of BMC. Thereafter, Mr. Crow will continue to be available on a consulting basis to the combined company for a period of time to support the integration execution and to ensure an orderly transition.

    Mr. Crow said, “This is a transformational opportunity that unites two outstanding and complementary companies, providing enhanced scale and superior returns as we build upon a new, larger platform. Builders FirstSource and BMC together will have a very diverse portfolio of value-added offerings and greater resources to more closely partner with and serve customers. The transaction is expected to produce tremendous value for the shareholders of both companies through the realization of significant cost synergies, the realization of attractive growth opportunities and the acceleration of technological innovation. Similar to the success of our prior acquisition of ProBuild, we will be poised to capitalize on the strength of our combined platform and the significant upside potential in our key end markets to increase sales, reduce costs and improve cash flow. We are excited about the opportunities ahead and look forward to quickly realizing the benefits of this transaction.”

    Mr. Flitman stated, “We believe this strategic combination of two great organizations is an exciting step forward for both BMC and Builders FirstSource, as well as for our associates, our customers and other key stakeholders. As we accomplished in our prior combination with Stock Building Supply, this transformational merger will enable BMC to further accelerate our profitable growth strategy with a company that also focuses on providing a broad product portfolio and differentiated capabilities deployed through a customer-focused service model.  Our customers and associates will benefit from the strengths of our exceptional teams, who share common values and a dedication to providing innovative services and solutions. We believe this compelling combination will enhance our ability to deliver outstanding customer service, generate attractive financial returns and create shareholder value. I look forward to working closely with Chad and the collective management teams of both companies to complete the transaction and further advance our next chapter of profitable growth.”

    Strategic Rationale and Financial Benefits of Winning Combination  

    • Leading Supplier of Building Materials and Services:  The combined company will become the nation's premier supplier of building materials and services, with combined sales in excess of $11 billion and approximately 26,000 team members. The combined company, operating a leading network of 550 distribution and manufacturing locations, will have a presence in 42 states, including 44 of the top 50 metropolitan statistical areas, covering most of the nation’s fastest growing regions.  
    • Enhanced Value-added Offerings: Benefitting from the focus on value-added product and service capabilities that both Builders FirstSource and BMC have long shared, these offerings will represent approximately 43% of the combined company’s sales. BMC’s distinct millwork capability, READY-FRAME® offerings and other manufactured products will complement Builders FirstSource’s strengths in trusses and manufactured components, among other offerings, to enable further penetration of key segments through the delivery of value-enhancing efficiencies to customers and superior solutions across a broader platform.
    • Expanded Geographic Footprint and Strengthened Distribution Network: The combined company’s increased geographic reach and diversity will provide a wider set of opportunities and deeper resources for organic and inorganic growth to meet the needs of more customers in the highly fragmented professional building materials industry nationwide. 
    • Significant Synergy Opportunities and Earnings Accretion: In addition to expanded top-line growth opportunities, the combination is expected to generate approximately $130 million to $150 million in annual run-rate cost savings within three years. Key drivers of these synergies include procurement, SG&A savings and expanded operational excellence through the adoption of best practices from each company. The transaction is expected to be accretive to adjusted earnings per share in the first year after closing. 
    • Strong Financial Profile and Capital Flexibility: The combined company will be supported by a strong financial profile, with combined Adjusted EBITDA(1) of approximately $950 million for the trailing twelve-month period ended June 30, 2020, including annual run-rate synergies, and combined net debt-to-Adjusted EBITDA(2)  of 1.4x. The combined company will remain operationally and financially disciplined with a focus on driving robust free cash flow, preserving its strong balance sheet and flexible capital structure to pursue a wide range of capital deployment strategies and deliver additional value to shareholders.
    • Accelerated Innovation: The combined company will have far greater resources to invest in innovation and develop targeted solutions, which is expected to accelerate the next generation of growth and deliver value on behalf of our customers.
    • Complementary Cultures: The combined company will bring together two strong performance-based cultures focused on people, safety, innovation, collaboration, integrity, diversity and corporate social responsibility. The collective workforce of highly skilled team members will benefit from expanded opportunities for career development and be empowered to provide best-in-class service to customers and communities.             

    Leadership and Governance

    Following the transaction closing, the combined company will operate under the name Builders FirstSource, Inc. and will be headquartered in Dallas, TX, while maintaining key functional corporate centers of excellence in both Raleigh, NC and Denver, CO.

    In addition to the succession of Dave Flitman as Chief Executive Officer of the combined company, the management team will be comprised of leaders from both organizations. Peter Jackson, Chief Financial Officer of Builders FirstSource, will serve as Chief Financial Officer of the combined company. The transition and integration of the combined company will be led by Dave Rush, Chief Operating Officer of Builders FirstSource’s East Region, who led the integration team for Builders FirstSource in its ProBuild acquisition, and Jim Major, Chief Financial Officer of BMC.

    Upon closing, the combined company’s Board of Directors will have 12 directors, consisting of seven members from the Builders FirstSource Board of Directors and five members from the BMC Board of Directors. Paul S. Levy, Co-Founder and current Chairman of the Board of Builders FirstSource, will serve as Chairman of the Board of Directors of the combined company.

    Mr. Levy commented, “We are excited to join forces with BMC. We started Builders FirstSource in 1998 with an ambitious vision, and the combination of these two exceptional companies represents another significant milestone, further enhancing value for all stakeholders. Our ability to continue to build our world-class organization exists because of the extraordinary commitment of our many teammates, led through many incredibly dynamic periods by Chad Crow and our prior CEO, Floyd Sherman, and we look forward to continuing that strong legacy of leadership under Dave Flitman. I have full confidence in the unified team to accelerate the success of this larger platform and continue building upon our powerful momentum into 2021 and beyond.”

    Timeline and Approvals

    The transaction is expected to close in late 2020 or early 2021, subject to, among other things, the expiration or termination of the applicable waiting periods under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, as well as other customary closing conditions. The transaction requires the approval of shareholders of both Builders FirstSource and BMC.


    2 ASHRAE Articles Underscore Importance of Healthy Buildings

    Energy EfficiencyBuilding Science

    Energy Efficiency & Building Science News published a popular article in June, Where Is COVID-19 and Building Science Leading ‘Healthy Buildings’?, in which Jay H. Crandell, P.E., ARES/ABTG, explores the finding contained in a recently completed research report titled Healthy Buildings & the COVID-19 Pandemic: Building Science for HVAC Systems and Building Envelope Best Practices.

    ASHRAE published two articles in the September 2020 issue of ASHRAE Journal that provide further insight into the importance of healthy buildings in the context of COVID-19:

    HVAC and COVID-19: Filling the Knowledge Gaps: Many HVAC-related factors could be significant regarding the spread of COVID-19. Increased ventilation, advanced filtration, humidification and improved mechanical hygiene are being included in measures intended to reduce its spread. A paper published in the September ASHRAE Journal summarizes what is known about the virus responsible for COVID-19 (SARS-CoV-2) and similar viruses regarding the role of HVAC in both the spread and control of infection.

    Improving IEQ to Reduce Transmission of Airborne Pathogens in Cold Climates: In cold climates, winter indoor environments often stabilize at a low relative humidity (RH) because of high outdoor air ventilation rates required for schools and high-occupancy office buildings. The low RH heavily affects indoor environmental quality. An article in the September ASHRAE Journal explores how improving indoor environmental quality through advanced HVAC equipment design for RH control can help reduce the transmission of airborne pathogens in cold climates and minimize energy efficiency impacts.

    For more information on the many ways building science is contributing to healthy buildings, check out these resources on continousinsulation.org.



    Designing and Installing Exterior Foam Correctly

    Energy EfficiencyBuilding Science

    Sherman Plumley of Resourceful Renovator in Richmond, Vt. Tim Healey

    If you’ve watched the evolution of energy codes over the past couple of decades, you’ve probably noticed an increasing emphasis on exterior insulation for walls. As early as 2006, the International Energy Conservation Code (IECC) specifically allowed exterior insulation as an option in its insulation tables. In the upcoming 2021 IECC, required insulation levels for walls are being stepped up, and choices are being added. As that happens, the option of insulating the wall exterior becomes more compelling. In many situations, augmenting cavity insulation with exterior foam will increasingly be the most practical alternative for builders.

    Exterior insulation has advantages. First of all, it substantially increases the true R-value of walls at a fairly low cost. For example, adding one inch of R-5 exterior insulation raises the real R-value of a 2x4 wall with R-12 cavity insulation from just R-10.7 to R-16. Secondly, most homes have framing factors of 25% (meaning that the true R-value of 25% of the windowless walls is the R-value of the wood, or R-3.5). Exterior foam insulation reduces thermal bridging across the wall through framing members, and it keeps the sheathing warmer (which reduces the risk of condensation and mold growth on the sheathing). But the practice of applying foam insulation to wall exteriors can be complicated, and it comes with some drawbacks. In particular, plastic foam is vapor impermeable, which means walls can’t dry to the outside if they do get wet. And foam sheathing doesn’t provide a positive attachment for the nailing fins of windows or doors.

    Over-framed walls like this lose a substantial amount of energy via thermal bridging. Exterior foam insulation overcomes much of this loss. Steve Easley

    To avoid callbacks caused by these factors, you have to address water and moisture management with greater diligence when you make the move to exterior foam insulation. And you may have to rethink the way you attach and flash your windows and do diligent inspections.

    The Advancing Code

    In the prescriptive tables of the upcoming 2021 IECC, a combination of cavity insulation with exterior insulation is strongly favored. In climate zones 6, 7, and 8, you can have either R-30 in the wall cavity, or a combination of R-20 cavity insulation with R-5 exterior insulation (R-20+5), or a combination of R-13 cavity insulation and R-10 exterior insulation (R-13+10). In climate zones 4 and 5, your options are R-20+5 or R-13+10. In climate zone 3, you can choose among R-20 in the cavity, R-13+5, or R-0+15. And in climate zones 1 and 2, you can choose between R-13 in the cavity or R-0+10.

    This infrared image shows the cold studs in a heated house on a winter day. Exterior foam insulation could prevent this source of heat loss. Steve Easley

    Extruded polystyrene foam is rated at R-5 per inch and polyiso at R-6.5 per inch. So depending on the options they choose, builders may need to apply an inch, 2 inches, or sometimes even 3 inches of foam. The energy benefit aside, there are practical problems to applying that much foam to a building exterior.

    Moisture Risks

    In the 1980s, we built a demonstration home at Purdue University that had heating and cooling costs of less than $200 a year. Part of how we accomplished that was by sheathing the exterior of the building with polystyrene. At that time, structural codes allowed us to install wood structural panel sheathing only at the building corners. But modern wall bracing codes in most regions require more extensive use of structural panels, and using continuous structural wood panel sheathing is the best way to get a stiff, rugged building. Although installing exterior insulation is still a way to get a high-performing building, there’s an increased level of risk when you cover a hygroscopic material like OSB sheathing with an impermeable material like rigid polystyrene foam. To forestall this risk, follow good moisture management principles and inspect everything before cladding is installed.

    Melted lines on a frosty wall show the heat passing through the wall at stud locations. Exterior foam insulation would make a difference.

    Moisture problems come from two places—they come from inside the home, or outside it. If there is a big moisture drive from inside to outside, and there is an impermeable material on the outside, that moisture is not going to dry to the outside so well. So you need to make sure that you pay particular attention to air-sealing. Do an air-sealing inspection before the insulation is installed.

    That’s because most of the moisture that enters the wall cavity from the interior is driven by air currents. And when the moisture comes in contact with a cold surface, it dampens that surface. If the surface relative humidity moves up above 70% or 80% range, then mold can start growing. How do you solve that problem? You prevent the moisture from getting there in the first place. You do that by providing good spot ventilation in the home, with bathroom and kitchen exhaust fans. Ideally, you should install technology that can automatically sense and control humidity.

    Good air-sealing becomes critical when walls are vapor-closed to the outside. Here, a builder did it right, as they have caulked the sheathing joint to the wall plate and the plate to the floor. (Yes, you need to do both.) Steve Easley

    The good news about exterior insulation is that because the insulation is outboard of the sheathing, that sheathing stays warmer. Warmer sheathing surface temperatures mean lower surface relative humidity. This means that the sheathing is less likely to dampen to the point that it reaches the threshold for mold growth. Even so, when you apply impermeable foam insulation to the outside of a building, you need to be fastidious about air-sealing the walls so that air currents across the wall are minimized.

    One option is to install the foam board first, then sheathe over it. That lets the sheathing dry to the outside. But if you build in a location where higher levels of wall bracing or shear walls are required, you’ll want to check with an engineer and make sure that the shear capacity of your sheathing is adequate. When sheathing is held away from the studs by insulation, its ability to resist racking forces is reduced.

    The Window Installation Puzzle

    Here, foam insulation has been applied directly to the studs, with sheathing applied outboard of that. Steve Easley

    Controlling the indoor humidity and building an airtight enclosure reduces the moisture risk from inside the home. That leaves the risk from outside the home—which is primarily found at penetrations like windows, doors and roof wall intersections. Most builders have plenty of experience at installing windows in a wood-frame wall without exterior insulation. But many builders may not have a usual method for installing windows when the wall has been packed out with an inch or two of extruded polystyrene.

    And while the code may require exterior foam insulation, the code doesn’t tell you how to fasten and flash the windows into that foam-insulated wall. However, there is a resource for builders: a document called FMA/AAMA/WDMA 500-16, which goes by the title “Standard Practice for the Installation of Mounting Flange Windows into Walls Utilizing Foam Plastic Insulating Sheathing (FPIS) with a Separate Water-Resistive Barrier.” This document is a joint production of the Fenestration Manufacturers Association, the American Architectural Manufacturers Association, and the Window & Door Manufacturing Association. Also be sure to follow the window, housewrap, and flashing manufacturers’ guidelines for their products.

    A lot of testing and thought went into the creation of FMA/AAMA/WDMA 500-16. Recognizing that the sequencing of the trades varies from builder to builder, the standard practice offers multiple alternatives for how to install the windows. In one method, housewrap is applied to the building before the window bucks and foam are attached; in another, the housewrap goes on after the bucks and the insulation. In a third method, the window is applied directly to the wall with no bucks. In every case, the flashing and housewrap are designed to direct water down and out of the wall assembly.

    ThermalBuck, an insulated window mounting system, creates a positive attachment for the window while limiting thermal bridging. Steve Easley

    In one version of Method A from the standard practice, the foam is applied directly to the sheathing and the housewrap is applied over the foam. The window buck (termed a “Rough Opening Extension Support Element,” or “ROESE,” by the document) goes on the wall first. The full sequence is as follows: window buck; insulating foam; housewrap (WRB); sill flashing; window; jamb flashing; head flashing; head tape.

    In another version of Method A, the housewrap is applied after the window is installed. In this version, the sequence is: window buck; insulating foam; skirt; sill flashing; window; jamb flashing; head flashing; housewrap (WRB); jamb tape; head tape.

    If you are concerned about thermal bridging at the window buck, or ROESE, consider a rigid-foam prefabricated product that is designed to take the place of the wood buck. The product shown here is called ThermalBuck.

    In this example, the window buck, window, drainable housewrap, and flashing have been installed prior to the application of the insulating foam. Always use a drainable wrap anytime you apply foam over the wrap. It’s important to carefully review window manufacturer installation instructions and warranties. Some window companies, for example, require “effective engineered drainage systems” for the warranty to apply. Steve Easley

    Method B describes a situation where the window is installed into the window buck over the housewrap, and the foam insulation is applied next. This method uses either fluid-applied or peel-and-stick flashing.

    Method C takes a different approach, applying the housewrap and the window to the wall before the foam is applied. In this case, there’s no window buck.

    For added security, I recommend that builders consider a rainscreen wall assembly. With a rainscreen, water striking the cladding has to jump across a ¼- to ¾-inch gap to reach the weather barrier, and even if that happens, the water just hits the weather barrier and runs down. So rainscreens provide you with exponentially better protection against water getting behind the foam.

    Here, a window buck and foam have been applied, the window has been installed, and then housewrap has been applied. When thick foam is used, window manufacturers may require metal jamb installation brackets to adequately support the window. Steve Easley

    Here, the window has been applied directly to the wall before the application of foam, and then housewrap and flashing are applied. Steve Easley


    ACEEE Publishes Several Energy Efficient Building Reports

    Energy Efficiency

    As we recently wrote on the ACEEE blog, the COVID-19 crisis has exposed the intertwined relationships among housing, energy, and health​, and has underscored how ​disparate living conditions can adversely affect communities of color. The health inequities revealed by the COVID-19 pandemic remind us of the urgent need to rectify the underlying conditions that make certain communities particularly vulnerable to health harms, and to ensure that every person has a safe space to shelter.  

    Here's an update on some of the work that the ​ACEEE Health and Environment team has been doing to bridge the health, housing, and energy efficiency sectors and align their efforts towards an equitable and healthy future.  

    We recently released a suite of reports that examine the relationship between health and efficiency, and identify opportunities to measure and monetize impact, expand innovative health services and leverage funding. These are available for download at the links below:   

    • Making Health Count: Monetizing the health Benefits of Services Delivered by Energy Efficiency shows that by targeting four common health risks — asthma, falls, and exposure to extreme heat or cold — existing weatherization programs could save almost $3 billion dollars in avoided health harms over a ten-year period. This study is among the first to quantify these potential savings and introduces a tool to customize and tailor calculations for specific programs at the state and local levels. 
    • Braiding Energy and Health Funding for In-Home Programs: Federal Funding Opportunities identifies 6 sources of health-related federal funding that represent $2 billion that could be used to provide weatherization and/or complementary services to households in need. By weaving together resources from the health and energy sectors, programs can access increased funding opportunities, expand services, and reach more households; such an integrated approach can yield environmental, economic, and health benefits, particularly for vulnerable communities.    

    These reports are first steps toward meaningfully bridging the health and energy sectors at the program level. To help share actionable knowledge with the on-the-ground practitioners who will turn these ideas into reality, we are also launching a new working group to support program implementers to incorporate health into energy saving programs. You can join the group by filling out a brief introductory survey here: www.bit.ly/aceeePDN.  


    A Cost Benefit Analysis of Energy Efficient Buildings

    Energy EfficiencyBuilding Science

    The home building industry is working to quantify the value that healthier, high-performance residential buildings can bring to occupants. Justifying the financials and the advantages of investing in durable, comfortable and sustainable buildings is especially fitting in the wake of COVID-19, as people are becoming more aware of what they want in their homes.

    The initial cost of a residential building is a primary calculation for builders, but what happens if that is co-mingled with considerations of the total cost of ownership, opportunity costs or other hidden values? These could include decreased number of doctor visits because of improved indoor air quality or fewer days of work missed from being sick.

    Tradeoffs occur when designing various features; opportunity cost is the potential profit loss when one option is chosen over another alternative. What costs and profit losses might occur when you choose to not build green? Evaluating costs and benefits can be multifaceted, so choosing one method over another might depend on a buyer’s priorities.

    Take multifamily residential buildings, for example. Turnover and recruitment of tenants can be expensive, including money lost when units are left vacant, money spent to clean and prepare a space when someone moves out, and investment in marketing/advertising to recruit new occupants for the space. Incorporating high-performance practices and features can positively impact the occupant’s experience, which could increase the chance that a renter will stay longer and reduce turnover costs.

    The Parkway, a garden style multifamily community in Houston, Texas, photography by Bruce Glass Photography. Read how The Parkway incorporated green features to increase the project’s marketability.

    Investing in high-performance construction strategies may come at a premium as you learn the specifics of green design, but many of the costs can be recouped. This case study — an above-code high-performance retrofit — demonstrated that savings per square foot from the following features made it less expensive to operate, off-setting initial costs:

    • The tight building envelope with insulation and air sealing reduced the required size and, therefore, cost of the HVAC system due to energy efficiency improvements;
    • Strategically placed operable skylights and windows and other daylighting techniques lessened the need for artificial lighting, which cut down on electricity usage and utility costs;
    • The exterior insulation provided more useable rental space; and
    • Building materials that help limit harmful chemicals, increase thermal comfort, reduce noise pollution and improve acoustics also enhanced the quality and comfort of the units and added significant value to the above-market rent.

    Increased occupant health and comfort associated with the highlighted strategies may also include decreased allergies, lower instances of asthma and increased productivity if the resident is working from home. Builders can learn more about how to clearly communicate these benefits by exploring Home Performance Counts, a new joint initiative from NAHB and the National Association of REALTORS®.

    The Parkway, a garden style multifamily community in Houston, Texas, photography by Bruce Glass Photography. Read how The Parkway incorporated green features to increase the project’s marketability.

    For more information about NAHB’s sustainable and green building programs, contact Sustainability and Green Building Program Manager Anna Stern. To stay current on the high-performance residential building sector, follow NAHB’s Sustainability and Green Building team on Twitter.


    PIMA Offers Live Course on Exterior Wall Fire Performance

    Press Releases

    PIMA is pleased to announce that its new live education course – Exterior Wall Fire Performance with Polyiso CI for Types I-IV Construction – is now available for member use. The course has been approved by AIA (1 LU | HSW credit) and ICC (0.15 credit) for continuing education credit. The course content provides an overview of Polyiso CI fire performance, introduces large-scale fire testing requirements, and explains the International Building Code provisions applicable to exterior walls. The course is available on the PIMA Advanced Wall Systems WG webpage.


    Green Homes 2.0: Sustainability and Resilience in New Construction

    Energy EfficiencyBuilding Science

    Extreme winters that evoke descriptors like “snowpocalypse” and “Chiberia.” Pummeling heat throughout the summer. Unrelenting wind and rain marking the calendar points where we used to experience spring and fall. Climate change is affecting life throughout Chicagoland and around the world.

    Still, the region has not seen large-scale, dramatic catastrophes such as the fierce hurricanes along the East Coast or wildfires like those that swept through parts of California last year. Lakeshore erosion and more frequent flooding on waterways like the Des Plaines River are alarming but have not generated the same sense of urgency. Mario Greco, founder of The MG Group at Berkshire Hathaway HomeServices Chicago, said that’s part of the reason why the Midwest is behind other parts of the country in terms of confronting the effects of climate change.

    “That doesn’t really seem to affect people,” Greco said. “There’s erosion along the lake. Beaches are disappearing. But that doesn’t really move people in the Midwest. I think Midwestern people are practical. They would rather spend less for gain now than spend more for gain later.”

    But still, shifts in the public perception of the planet are impacting the new construction world in Chicagoland. For some, the solution involves environmentally sound green homes that utilize sustainable materials in their construction to help mitigate the human impact in the environment. But also, the concept of resilience has also become part of the conversation as homebuyers seek out buildings designed to withstand the stresses of environmental change.

    Residential greenery gains traction

    Green homes are nothing new. The U.S. Green Building Council was established in 1993 by more than 60 architectural firms and nonprofit groups that sought to develop a rating system for eco-friendly buildings. Their goal was to create better buildings with people and nature in mind. The Leadership in Energy and Environmental Design, or LEED, building certification program evolved through the council to verify that a structure met certain metrics in terms of energy efficiency, water usage and the utilization of renewable or recycled construction materials.

    In the nearly three decades the organization has been around, the conversation has moved beyond the basics. Wellness considerations are also a factor and are becoming a bigger part of the equation for people who want green homes.

    “Efficiency is a hot topic, and that’s something that helps homes improve their performance and also can lead to financial savings,” said USGBC West North Central Regional Director Sheri Brezinka. “I think one of the biggest trends that we’re seeing and that we’re really hoping it’s going to gain more traction is the emphasis on personal health and well-being. I think people are really starting to understand the impact of LEED on what we call indoor environmental quality.”

    Structures such as schools, municipal buildings and even grocery stores can be built according to LEED standards. Builders are also approaching new-home construction with those guidelines in mind, as evidence of climate change and higher costs associated with traditional building practices pile up.

    The Chicagoland region has long been one of the top markets for LEED certification, according to Brezinka. The majority of those certifications are granted to commercial buildings, but there also has been an increase in homeowners seeking the status.

    “Because people are familiar with the certification, it really does set a mark for showcasing that a LEED building is a more sustainable, high-performing building,” Brezinka said, noting that the number of homes with LEED certification has jumped by 19 percent nationally since 2017. “That’s an all-time high. So, we’re excited to see the residential market is starting to uptick not only in Chicago, but across the country.”

    USGBC’s “LEED in Motion: Residential” report, released last summer, states that there are more than 400,000 LEED-certified housing units in the United States out of nearly 500,000 worldwide. Illinois had 2,408 LEED-certified residential units at the time of the report, which ranked the state 19th in the U.S. But in terms of its square footage of green projects completed per person in 2019, Illinois came in second in the nation at 3.95 gross square feet per capita, according to the USGBC. That figure encompasses 121 total projects and includes commercial structures.

    John Goldsworthy has had a front-row seat in this recent expansion of LEED-certified residential space in Chicago. The broker and manager of development sales and marketing at @properties works with builders who put up sustainable and resilient structures, as well as renovate existing buildings to make them more environmentally friendly. He represents the developers of the 1000M condo building that’s going up at 1000 S. Michigan Ave. in Chicago’s South Loop. That project is being developed with LEED certification in mind. Features designed to lessen the 74-story tower’s impact on the environment include the use of core building materials that are sourced from within a 500-mile radius and those that contain high levels of recycled materials.

    “The overall goal is to try and diminish or avoid sending a large stream of damaged or used material to landfills,” Goldsworthy said. “It’s about switching the mindset from cheap and short term to items and building materials that are worth a bit more in the long run.”

    Resilience and reality

    Climate change poses major questions for builders. What sorts of problems will their buildings face? For people in coastal areas, rising water levels and storm intensity immediately come to mind. Chicagoland’s proximity to Lake Michigan and rivers such as the Chicago and Fox make it vulnerable to similar threats. The region also faces the threat of more precipitation, hotter temperatures and increased humidity, according to Openlands, a conservation organization based in the region. Higher temperatures are not only uncomfortable but also expected to contribute to more intense storms.

    Greco believes municipalities in the Midwest need to respond to climate change by making it easier for builders and homeowners to utilize environmentally friendly features.

    “Cities like Chicago need to make the permitting process for — for example — geothermal heating and cooling, solar panels, and other green features, easier, more streamlined and more public,” Greco said, adding that homeowners who act now will be able to reap the rewards sooner than they may think. “What people need to keep in mind is that things are changing pretty quickly. If you can get ahead of the curve by putting some green features in your home, maybe in the next five or 10 years when I think it’s going to be a much more urgent matter, you might be able to come out ahead when you’re selling your home.”

    Resilience construction takes some of the same principles from green construction standards and applies them to the practice of designing and constructing buildings that can withstand the environmental stresses of climate change. Stronger materials, innovative building techniques and a tighter building envelope are all major elements in resilience construction. Homes elevated on stilts in coastal areas could be considered examples of resilient construction, as they are designed in response to the looming threat presented by weather events like hurricanes.

    Brezinka said that resilience construction often makes use of durable materials. Site selection is part of the process, including considerations such as orienting the building to withstand wind or make use of the sun in lighting. Rainwater collection, energy efficiency, and site renewal and regeneration — practices that restore natural elements such as coastal marshes that can absorb some of the effects of extreme weather — are also elements of resilience construction.

    Thankfully, the twin concepts of sustainability and resilience work together. “All of these strategies that are used in green buildings and homes are also strategies that contribute to helping people to prepare for severe events and to recover from those events that do happen,” Brezinka said. “We see that green [construction] as a cornerstone of resilience. I think that people are really starting to recognize that sustainability is more than just reducing our impact on the environment. Way back when we started with LEED, it was really about reducing environmental impact. But as years have gone on, we’re looking at creating homes and buildings that are designed to help support us if there are severe events that happen.”

    Goldsworthy pointed to the 1000M building as an example of a new structure that incorporates resilient elements in response to climate change scenarios that are likely to affect the Great Lakes region. Its features include a green roof and storage tanks designed to hold runoff from severe rainstorms so that it can be released gradually, without taxing the city’s sewer system.

    “We’ve converted our roof surface area to a green roof,” Goldsworthy said, adding that sky-high gardens also lower the temperature of the tops of buildings. “We see that trend growing as the city is requiring that more and more to keep the thermal envelope down. Water retention and storage are becoming a big issue with our outdated or antiquated sewer systems in the city.”

    The value proposition

    Misconceptions regarding green homes persist. Brezinka finds that people often think a green or resilient home is more expensive to build, that green materials are hard to find or that such structures are too costly to maintain. Agents who want to sell green homes should be prepared to discuss long-term benefits that outweigh the price premium on LEED-certified units.

    Brezinka noted that while green building materials and certifications might cost more at the outset, that initial outlay is recouped in the form of lower energy bills and higher resale value.

    “Certified homes undergo inspections; there’s detailed documentation, reviews, they’re performance tested, so they’ve been proven to make sure that they’ve been built in a way that can protect the health and safety of the homeowner,” she said. “There are so many key benefits that the homeowners should be aware of, like the savings through energy-efficient measures and water that can not only help the environment but can lead to more affordable utility bills.”

    Greco said agents need to be prepared to communicate the value proposition that goes along with green features to their clients, both the more obvious payoffs and the subtler ones.

    “Sometimes the savings aren’t immediate,” Greco said. “In the long run, I think green features are not only going to keep their value, but actually make properties easier to sell. I think environmental and climate change concerns are going to be growing exponentially in the next few years.”


    USGBC Announces LEED Homes Awards Recipients and Residential Project of the Year

    Energy Efficiency

    The U.S. Green Building Council (USGBC) announced the recipients of the annual LEED Homes Awards. The awards recognize LEED-certified residential projects that are positively impacting communities through sustainable, healthy and resilient design, as well as builders and developers who are helping to advance green home building. Recipients represent multifamily, single family and affordable housing projects from around the world, including the U.S., Mexico and Turkey. This year’s Project of the Year is Park Mozaik A Block in Ankara, Turkey.

    “As communities around the world are grappling with how to address the economic and health challenges we’re facing, it’s never been more important to commit to the development of green homes that help families lower their utility payments and enhance their health and well-being,” said Mahesh Ramanujam, president and CEO, USGBC. “The LEED Homes Awards recognizes the residential builders and developers committed to LEED who are leading the industry to a sustainable, resilient and healthy future. This year’s recipients are examples of what we can achieve when we prioritize decisions that support both people and the planet, especially for our most vulnerable communities, and they remind us that each certified green home is an opportunity to improve someone’s quality of life.”

    The full list of this year’s LEED Homes Awards recipients include:

    Outstanding Multifamily Project:
    – Iconia Cubos Luxury Living, Guadalajara, Mexico
    – Park Mozaik A Block, Ankara, Turkey (Project of the Year)
    – Sitka Apartments, Seattle, Wash.

    Outstanding Single-Family Project:
    – GPD 346 Highland, Weston, Mass.
    – GREENLAB, Dallas, Texas
    – Sikes Residence, Cincinnati, Ohio

    Outstanding Affordable Project:
    – 3365 Third Ave, Bronx, N.Y
    – The Arroyo, Santa Monica, Calif.
    – Freedom Commons, Syracuse, N.Y.

    Outstanding Developer:
    – AMLI Residential

    The awards also recognize LEED Homes Power Builders—an elite group of developers and builders who have exhibited an outstanding commitment to LEED and residential green building. At least 75 percent of each Power Builder’s homes/unit count from 2019 achieved LEED certification.

    This year’s group includes:
    – Active West Builders
    – AMLI Residential
    – Brookfield Properties
    – Frankel Building Group
    – Gables Residential – DC Metro
    – National Community Renaissance
    – Maracay Homes
    – MHI Dallas
    – MHI Austin
    – Tierra Realty Trust

    Achieving LEED certification is an indication that a home meets the highest sustainability standards. A LEED-certified home helps lower utility bills by reducing energy and water consumption and provides a healthier indoor environment by improving air quality and using materials that lower people’s exposure to toxins and pollutants. LEED also serves a roadmap for creating high-quality, affordable housing that improves quality of life. The number of LEED-certified green homes continues to grow globally with certifications increasing 19 percent from 2017 to 2019. Currently, there are more than 555,000 LEED-certified residential units around the world.


    Study Recommends How to Reduce Home Energy Consumption

    Energy EfficiencyBuilding Science

    Americans’ homes are energy hogs. This is because houses in the US are much larger than houses in other countries, says a new study from University of Michigan researchers. Further, larger, wealthier US households produce around 25% more emissions than their lower-income counterparts in smaller homes.

    For example, according to 2010 data from the World Energy Council (via Shrink That Footprint):

    In the US, typical household power consumption is about 11,700 kWh each year, in France it is 6,400 kWh, in the UK it is 4,600 kWh, and in China around 1,300 kWh. The global average electricity consumption for households with electricity was roughly 3,500 kWh in 2010.

    The University of Michigan study looked at 93 million homes’ 2015 tax assessor records. The researchers examined houses’ size, age, location, and construction date. The study states that the average US home consumed 147 kilowatt-hours per square meter (kWh/m2) in 2015.

    What US households need to do

    The study’s abstract states:

    Grid decarbonization will be insufficient to meet the 80% emissions reduction target for 2050 due to a growing housing stock and continued use of fossil fuels (natural gas, propane, and fuel oil) in homes. Meeting this target will also require deep energy retrofits and transitioning to distributed low-carbon energy sources, as well as reducing per capita floor space and zoning denser settlement patterns.

    Benjamin Goldstein, a co-author of the study, says Americans need to rethink how they live:

    Structural change is going to be important and necessary. We need to have denser and smaller homes.

    Reuters reports that home sizes have been trending downward since 2015, according to builders, and congressional Democrats unveiled a climate policy blueprint earlier this month that calls for an update of building codes to eliminate greenhouse gas emissions. Further, there is a growing movement to ban natural gas in new homes; San Francisco recently proposed this measure.

    And why wouldn’t Americans want to reduce energy consumption right now? In addition to the importance of reducing emissions, people are spending more time at home than ever due to the pandemic, so they’re using more electricity at home, and money is tight for a lot of households.

    Do energy-efficient appliances work?

    There are a lot of ways to reduce energy consumption and emissions, such as better insulation and either installing rooftop solar or joining a community green energy plan such as Arcadia. Further, turn your air conditioning temperature up this summer and get a smart thermostat.

    But let’s take a look at some energy-efficient appliances, which have been thrown into the political spotlight recently by Donald Trump as being ineffective. Snopes rated Trump’s claim as false. Here’s how they actually reduce a household’s energy consumption without compromising quality:

    Toilets: Peter Gleick with the Pacific Institute in Oakland said, “New toilets not only use a tiny fraction of the water the old toilets used to use, but the truth is they flush better — and if you have a bad toilet that doesn’t flush, well, that’s because you have a bad toilet.”

    Showerheads and faucets: As the Lebanon Democrat reports, “Standard shower heads use up to 8 gallons of hot, steaming water per minute. With a new, low-flow shower head, you will only use 1 to 2 gallons of water per minute. Faucet aerators cost about $5 and work much the same way. You probably won’t notice a difference, but you will on your utility bill.”

    Water heaters: These use up a lot of your household electricity. Replace old models with tankless water heaters if possible, and comparison shop — here’s Consumer Reports‘ take on the most efficient water heaters. And in the meantime, turn your water heater temperature down to 120F. It’s plenty hot, and it will cut water heating cost by 6% to 10%.

    Dishwashers: Today’s dishwashers currently use 5 gallons of water per cycle — half the amount of water and energy that standard dishwashers consumed 20 years ago, according to the Natural Resources Defense Council. And they clean dishes just fine. Soil sensors in most machines ensure dishwashers take only as long as they need to clean dishes.

    Light bulbs: Using incandescents are a waste of money and energy. Again, according to the NRDC:

    LED light bulbs work great and consumers like the light they provide. LEDs are better than incandescents because they use up to 85% less energy to produce the same amount of light. They last 10 to 25 years while incandescents burn out and need to be replaced every year or two. An LED bulb sips rather than gulps electricity, saving consumers $50 to $100 over its lifetime.


    RESNET Releases Trends in HERS Rated Homes

    Housing & Construction

    Each year more than one-fifth of all new homes built in the U.S. are rated for their energy efficiency using the Residential Energy Services Network’s (RESNET) Home Energy Rating System (HERS®) Index.

    Developed by the Residential Energy Services Network, or RESNET, a HERS Index Score is available only via certified RESNET Energy Raters. Based on several variables that affect the energy efficiency of a home, including exterior walls, attic, windows and doors, heating and cooling systems, ductwork, water heating systems, lighting and appliances, the HERS Index Score tells homeowners and prospective buyers how their homes compare to other similar homes in terms of energy usage.

    RESNET has posted a new report that provides a unique glimpse on how homes are built today and the dramatic increase in the energy performance in new homes. The report, “2020 Trends in HERS Rated Homes”. This report is the first of its kind to look at the construction and efficiency trends across all homes receiving a HERS rating in 2019.

    The report looks at

    • Broad national-level trends in the number of HERS ratings and average index scores.
    • State-level trends, including the total number of HERS ratings in each state and the percent of new homes that received a HERS Rating.
    • Trends of HERS ratings in cities, including the top 25 cities for single-family and multi-family ratings.
    • Individual trends across HERS ratings, including a breakdown of the basic characteristics of rated homes and individual building components.
    • The report concludes with a first-of-its-kind look at the demographics of buyers of HERS rated homes based on a 2019 study conducted by mortgage industry giant Freddie Mac.

    In 2019, HERS Raters rated almost 242,000 homes. This represents nearly 100,000 more ratings than were completed in 2013 and marks the eighth straight year-over-year increase in HERS ratings. In addition to the record number of HERS ratings, the efficiency of HERS rated homes also improved. The average HERS Index in 2019 was a 59, representing a 41 percent improvement in efficiency over a home built in 2006. Since 2013, the average HERS index score has decreased by four points. Seventy-seven percent of all homes rated last year were one- and two-family dwellings and 23 percent were multifamily units. In 2019 there were HERS Ratings completed in more than 4,000 individual municipalities. San Antonio, Texas tops the list of municipalities with the highest number of HERS Ratings at more than 4,200 homes. The top 25 municipalities are located across seven states and are responsible for nearly one-fifth of HERS Ratings last year.

    As a national aggregate, the average single family HERS Rated home had the following basic characteristics in 2019:

    • HERS Index Score: 59
    • Number of bedrooms: 3.7
    • Conditioned floor area: 2,775 ft2
    • Number of floors: 1.6
    • Annual energy cost: $1,707
    • Annual energy cost savings: $789
    • Annual CO2 savings: 2.6 tons

    The average multi-family dwelling unit had these basic characteristics in 2019:

    • HERS Index Score: 59
    • Number of bedrooms: 2.2
    • Conditioned floor area: 1,384 ft2
    • Annual energy cost: $1,118
    • Annual energy cost savings: $504
    • Annual CO2 savings: 2.5 ton

    Click here to download the full report.