Energy Efficiency and Building Science News

Grenfell BRE Report: If Code Followed, Likely Wouldn't Have Happened

Tue, 2018-04-24 10:31
Building CodesBuilding Science

A Building Research Establishment (BRE) report summarizing the investigation into the deadly Grenfell Tower fire last year in London has been leaked, and several causes for the tragedy were identified. Each of the following excerpts from the report are linked to the online report. Each of the BRE excerpted report pages are also linked at the end of this article.  


The report states that Grenfell Tower as originally constructed provided “very high levels of passive fire protection,” but that a refurbishment undertaken between 2014 and 2016 was not performed correctly, and opened multiple avenues for fire spread, in the event of an accidental fire.



Essentially, the report makes clear that had the refurbishment been completed to code, it is highly unlikely the fire would have spread beyond the original flat nor would there have been any loss of life. 


Building code requirements in the United States are comparable, if not more exacting, than those that applied to the construction of Grenfell Tower. It is clear from the report’s conclusions that enforcement of the code is the most effective way to prevent similar occurrences both in the U.S. and U.K. To understand why, it’s vital to look at the conditions that led to the rapid fire spread.


Between 2014 and 2016, Grenfell Tower received a new cladding and insulation system as part of a refurbishment.  The BRE report notes that both the insulation and the aluminum composite panels used provided combustible fuel for the fire. These materials have been used successfully for many years, and when installed in a code-compliant manner, are properly separated from living spaces and use detailing to prevent the spread of the fire inside the wall to the next higher floor.


In the case of the Grenfell Tower refurbishment, however, key details were ignored which allowed the fire to reach the cladding, and once there, to spread without check.  New windows were installed in a way that “lacked any barriers to fire spread between flats and the cladding system” and cavity barriers in the cladding system meant to expand to block off the cavity during a fire were too small to expand fully, and in many cases, improperly installed. 



These shortcomings allowed the fire to easily move from interior living space to the exterior façade (and vice versa), and spread quickly across the façade. 



Fortunately, when buildings similar to Grenfell Tower are constructed in the U.S., they are subject to the International Building Code (IBC).  The International Building Code (IBC) directs builders and designers through a series of questions when it comes to cladding exterior wall systems. These questions include:

  1. What is the building occupancy? IBC Chapter 3.
  2. What type of building is it? IBC Chapter 6.
  3. What is the building’s height and area? IBC Chapter 5.
  4. How close is the building to other buildings? IBC Chapter 6.
  5. Will it have a sprinkler system? IBC Chapter 9Chapter 14.
  6. Does it need to meet the NFPA 285 test standard? IBC Chapter 14Chapter 15, and Chapter 26.

With limited exceptions for some one-story buildings, Chapter 26 of the IBC requires buildings of type I-IV construction of any height which contain foam plastic insulation to comply with National Fire Protection Agency standard 285 (NFPA 285).  To comply, testing and professional engineering analysis are performed where the proposed wall and cladding system is subjected to fire exiting from a window (as happened with the Grenfell Tower). To pass, fire tests and related professional engineering analysis must show that fire spread vertically or horizontally along the cladding beyond the immediate area is less than the time it would take for the inhabitants to evacuate. 


The IBC also requires all high rise buildings to include an automatic sprinkler system.  The BRE report states that had a sprinkler system been installed in the Grenfell Tower, it “could have significantly altered the outcome of the fire” by putting out the fire before it left the original apartment.



Given the report’s conclusions regarding the construction detailing and the resulting spread of fire in the Grenfell Tower event, a key questions is: “Does this event reflect expected fire resistance performance, in code compliant construction, in a way that should cause significant regulatory changes for U.S. buildings?”  

It seems clear from all the information available, if designers, builders and installers perform in a manner that conforms with the requirements of the IBC, the 30 years of demonstrated effective and safe performance, when using NFPA 285 and IBC Chapter 26, will continue.

For more in depth information on fire safety and the use of foam sheathing, read this recent document created by the American Chemistry Council’s Foam Sheathing Committee (FSC).

For additional information about this topic please review:

Here are links to the 13 leaked pages from the Draft BRE Report:

Author: Kirk Grundahl, Tim Ahrenholz, Sean Shields, Larry Wainright and TJ Jerke

Weyerhaeuser to Distribute Owens Corning XPS Line

Mon, 2018-04-23 21:06
Building Science

Weyerhaeuser Distribution will stock the full-line of the FOAMULAR® XPS portfolio at its distribution centers in Denver, Salt Lake City, Albany, Ore., Boise, Idaho, and Tacoma, Wash. Owens Corning, a leading global producer of glass fiber reinforcements for composite systems, manufactures the FOAMULAR® XPS insulation family of rigid foam boards for both residential and commercial building solutions.

The comprehensive line of FOAMULAR® products includes a broad choice of sizes, thicknesses and edges for ease of installation, as well as compressive strengths found in light residential through to the heaviest of industrial floor loads. Its high resistance to moisture coupled with its R-value make it a great solution for excellent thermal and moisture control throughout the building's lifecycle.

Available product lines will support residential and commercial applications comprised of wall sheathing, including interior basement walls, re-siding, under slab and exterior wall foundations.  Add to that complementary Owens Corning® accessories for a complete insulation building solution.

"We are committed to supporting our customers with forward-thinking approaches to meeting changing codes in our growing communities," said David Helmers, vice president of Weyerhaeuser Distribution. "FOAMULAR®, a proven leader in building insulation systems, allows our west coast facilities to guide builders through the selection process for their homes and buildings."

Not only durable, FOAMULAR® XPS insulation is GREENGUARD Gold certified for indoor air quality standards, is the only XPS foam with third-party certified recycled content-certified by SCS Global Services with an average of 20 percent recycled content and contributes to the LEED® Green Building Rating System.

"We are excited to be working with Weyerhaeuser in our combined efforts to help builders build structures with long lifespans," said Julian Francis, president of Owens Corning's Insulation Business. "Our partnership with Weyerhaeuser provides a wonderful opportunity to better serve our customers and grow our business on the west coast."


Kingspan’s New Rigid, Fiber-Free Cavity Insulation

Mon, 2018-04-23 21:04
Building Science

Kingspan has developed a rigid thermoset fiber-free insulation called Kooltherm K8 Cavity Board, which is suitable for a host of installation applications including wall, floor, soffit, rainscreen, and concrete sandwich wall systems.

The closed-cell structure of the insulant protects against moisture and water vapor ingress, and offers fire protection. Kooltherm is covered on both sides with a low-emissivity composite foil for improved thermal resistance of any unventilated cavity adjacent to the board and has an R-value of up to 16 per 2" thickness.  Its core is made of a high-performance rigid thermoset fiber-free phenolic insulant. Further, the insulation core and facings resist attack by mold and microbial growth and do not provide any food value to pests.

This product is manufactured with a blowing agent that has zero ozone depletion potential (ODP) and low global warming potential (GWP). Kooltherm's standard size is 47.25" wide by 16" long.





Comparing Two Leading Interior Vapor Barrier Products

Mon, 2018-04-23 20:54
Building Science

As most building science nerds know, in the past five years we have been inundated with new products to help us build to Passive House or Net Zero standards. You would assume that most of the building science professionals have a good handle on all of the latest products, however, some recent conversations with experts in the field led me to believe that there is still a lot of unknowns. Like myself, many “experts” are still overwhelmed with finding the best approach for controlling moisture in walls and products that can assist in achieving air-tightness, while allowing vapor permeability in the right direction, as well as understanding human health impacts of the chemicals used in the materials.

A little background for the layman:

In the last few decades there has been a push to be build tighter building envelopes. Initially, the industry had not yet opened the doors to balanced ventilation using ERVs and HRVs, and even today, we are still building exhaust only ventilation systems. As buildings got tighter, ventilation systems didn’t change and thus did not have proper air circulation. When people started getting sick from mold and lack of fresh air, the term “sick building syndrome” was born and many people found out the hard way that tighter, didn’t always mean better when it came to human health. Where older buildings had relied upon air leakage for fresh make-up air, these newer buildings were tighter and thus started trapping moisture, which allowed mold to grow within the walls, feeding off wet wood and drywall, hidden from the occupants within the wall. There were many instances of people becoming quite sick due to exposure to mold spores and fungal growth within their homes and work places. I personally have seen buildings with mushrooms growing out of the wall around windows and doors.

So, back to today. We now know that in order to build energy efficient building envelopes, we need to create an airtight layer, but we also need to make sure we control moisture within the walls. The main sources of moisture are: 1. Outdoor Water (rain), 2. Exterior Humidity and 3. Interior Humidity. When we build a tight envelope to achieve Passive House for instance, the design suddenly becomes a bit more complicated that previously. We need to understand the basics of temperature differentials inside and outside the building and dew points, to know where there may be potential for condensation accumulation. Though we can control fresh air through mechanical means, we can’t however always dictate moisture build up within the building envelope. So in order to build high performance buildings that are also durable, we need to know how our building products work, especially key components like air and vapor barriers.

Vapor Barriers:

Two of the leading interior vapor barriers being used today for Passive House and high performance projects are SIGA products and Pro Clima’s Intello Plus membranes. Both companies have products which are Passive House Certified components.

  • But what are the differences between SIGA’s Majrex and Intello?
  • Does one perform better than the other?
  • Which product is best for my project?
  • Does one product meet higher health standards than the other?
  • What are the products made of? Are they recyclable?
  • What are the cost differences?

As I mentioned, many people in the industry are still confused on which product they should be using for their particular application. So I’ve done the digging so you can just read and make a choice for yourself.

SIGA Majrex vs. Pro Clima Intello Plus

SIGA Majrex:
The SIGA, Majrex membrane was designed based on the natural moisture balance of a cactus which SIGA calls Hygrobrid technology. A cactus allows for moisture into the plant at night to trap the moisture inside during the day, to prevent the plant from drying out in the hot/dry desert climate. Similar to the cactus, Majrex allows the moisture to move from within the wall to the inside of the building but doesn’t allow interior moisture into the wall. This is called “one direction vapor transportation”, as moisture only moves to the interior.  (I do like how they are using biomimicry to describe the product.) One directional drying helps to prevent microbial growth from building up from condensation that becomes trapped within or continually moves through the wall. Moisture within the building can then be addressed though ventilation (HRV or ERV). Majrex provides permability ratings for both sides of the membrane, Direction 1: 0.17-3.8 perm (ASTM E96) Direction 2: (the logo side) 0.16-1.3 perm, indicating the interior side is less permeable as described above. Majrex is 12 mils thick and comes in 4.9 ft width and 164 ft long rolls.

Pro Clima – Intello Plus:
Intello Plus by Pro Clima is known as a vapor variable retarder, which claims to have “adjustable permeability” based on humidity levels. In the winter, when the air is dryer, the permeability of the material remains low, to prevent wetting of insulation from interior moisture. In the summer, when relative humidity is high, the material opens further to allow max diffusion openness, to increase drying potential to the interior. Intello’s variable permability ranges from 0.2 – 6 perm (ASTM E96) (DIN EN 1931 <0.13m to 13.2m) and is 16 mils thick. The rolls come in 5 ft and 10ft wide and 65 ft and 164 ft long. Pro Clima claims the product is fully recyclable as it is made of polypropylene microfiber fleece, vapor variable polyethelene co-polymer with polypropylene non-woven fabric. The tape used with Intello Plus is Tescon Vana.

Product Health:

With regards to transparency in material health and chemicals, Intello Plus wins. Intello Plus not only has a ILFI’s (International Living Future Institute) Declare Label, it is also “Red List Free” meaning that the product has been inspected for all chemicals on the Red List, which is used by the Living Building Challenge to eliminate the use of the highest risk chemicals on projects. SIGA’s rep mentioned that they don’t use any harmful chemicals, but said that they have chosen not to pursue the Declare Label for proprietary reasons.


COST: The SIGA product was slightly more expensive. I received quotes from local vendors in the north east, Intello running about $323 for a 4.9 ft – 164 ft roll and SIGA $377 for a 4.9 ft 164 ft roll. Winner: Intello Plus

HEALTH: Intello Plus has no “Red List” chemicals and has been transparent about the chemicals used in the product using ILFI’s Declare Label.  SIGA has not provided chemical transparency and is looking to provide more information. Winner: Intello Plus

PERFORMANCE: Performance between the two products isn’t a simple answer unless we see failures in the field or if some specific testing is done. I believe that climate zone may dictate which product performs better, however this is just an assumption. Both products have been approved by the Passivhaus Institute as “Certified Components” which gives some added assurance that both products would perform quite well in a Passive House setting. From reviewing the product technical data and discussions I had with each of the product representatives, I’ve come to the following assumption: Areas with highly variable temperature and humidity, like we have here in the North East, Intello may be the better choice as it adjusts based on humidity and temperature. In areas with less variability in climate, SIGA might be just as effective if not the better choice, however I’m interested to see how each product performs over the next 10-20 years. Winner: Undetermined

SUSTAINABILITY: Both products claim to be recyclable, however the SIGA Majrex seems to be only recyclable in certain areas of the country, whereas the Intello Plus is claiming to be 100% recyclable.  Winner: Intello Plus

Overall, both products were developed with what seems a lot of research and testing backing up their performance. Both products serve as air sealing and vapor barrier membranes, though the specifics of performance do vary. Considering the categories we reviewed, the Intello Plus seems like the logical choice, especially if product transparency and health is a concern. However, we look forward to hearing from contractors installing these and other products like them, to give a clearer picture of how vapor barriers perform across the industry.


Austin to Host Conference on Humid Climate Construction

Mon, 2018-04-23 20:39
Building Science

The Passive House Austin (PHAUS) Chapter will be hosting its annual Humid Climate Conference May 21-22, 2018 in Austin, Texas. This two-day event is focused on design considerations for humid climates with substantial cooling loads. The conference offers eight CEU hours to attendees and features experts in the field including, Dr. Joseph Lstiburek, Lew Harriman, Jonathan Bean, Marty Walsh, Claudette Reichel, and Richard Corsi.

Registration is limited to 250 attendees, and over 100 have already registered.




Author: Sean Shields

Video: Builder Shows How to Insulate and Vent Stucco

Mon, 2018-04-23 20:14
Building ScienceEnergy Efficiency

Based in Austin, Texas, Matt Risinger is a new generation of homebuilder who regularly blogs and reviews new building products and methods as he uses them in the homes he builds. Recently, he made this video detailing how he installs a traditional three-coat stucco wall with a drainage plane and exterior insulation:


Author: by Matt Risinger

Net-Zero Project's Unique Use of Spray Foam

Mon, 2018-04-23 20:08
Building ScienceEnergy Efficiency

Zero Net Energy (ZNE) will soon be the overriding goal driving the residential building industry.

Over the past decade, interest and activity in ZNE have markedly increased. More and more custom homes designed for ZNE have cropped up, and many production builders are currently planning ZNE new home communities, even if those communities represent their first endeavor in the space. Pre-fab options are also gaining traction, and the movement overall has grown in momentum, with ZNE project case studies and solutions now figuring more prominently in industry conferences.

Net zero momentum

"The net-zero building movement is rapidly gaining momentum -- the number of net-zero energy buildings nationally is on a steep upward curve and has increased 700 percent since 2012, " said Drew Shula, founder and principal with Verdical Group and organizer of the Net Zero Conference held annually in Los Angeles, which is expected to draw close to 1,000 attendees in September. "Just as the LEED green building rating system took off on a trajectory up and to the right about 15 years ago, the net-zero building movement is poised to do the same in the decade ahead."

Within the residential sphere specifically, some standout projects were delivered to market this past year. One such home, the Jacobson House in Northern California, garnered the spotlight with its unique story and innovative energy solutions.

The home belongs to Stanford professor Mark Z. Jacobson. His commitment to living in an Earth-friendly home aligns with his role as head of the university’s Atmosphere and Energy Program. A climate and clean energy scientist, Jacobsen is also one of the founders of The Solution Project, a program to accelerate the transition to 100 percent renewable energy use in the United States. His new home enables him to practice what he preaches.

The home sits on an irregular pie-shaped lot near Stanford’s campus. An abode designed by BONE Structure, the Canadian prefab homes company, the Jacobson house has been compared to a giant erector set. Snapped together in under a week, the 3,200-square-foot modular home includes a frame comprised entirely of steel, of which 89 percent of the material used is sourced from recycled content and is expected to last centuries longer than a wood frame.

The home is also designed to use no consumer electricity and generates zero emissions. Powered by solar panels, all excess energy is stored in large Tesla batteries. There is no natural gas line leading into the property.

“This home is exciting for a variety of reasons including its tie to a world-class scientist, its unique prefab construction and its overall energy generating technology and performance,” said Kurt Riesenberg, executive director of the Spray Polyurethane Foam Alliance, one of the sponsors of the Net Zero Conference. "The most exciting part of this to me, however, is how the project uses spray polyurethane foam insulation to conserve the energy. The SPF industry has always contended that there is no better compliment to distributed or onsite energy generation than spray foam. Who wants to invest in technology and engineering just to put it in service on a building that leaks like an air-filter?”

The home’s metal framing provides improved structural performance for the walls. While somewhat typical in commercial construction, metal framing can create unwanted thermal bridging. But in this home, horizontal framing was applied perpendicular to vertical framing to minimize heat loss through metal studs, while maintaining a fastening surface to the exterior cladding.

The area between the horizontal and vertical horizontal studs was insulated and air sealed with spray polyurethane foam insulation, in an approach consistent with high-performance walls as emphasized in the state of California's 2019 Building Energy Efficiency Standards for Residential and Nonresidential Buildings (i.e., Title 24).

SIPs were used for the low slope roof structure. While SIPs provide continuous insulation, they must be properly sealed at all joints and wall connections. Open-cell spray foam applied below the roof deck provides backup insulation and air sealing for the SIP roof structure.

Airtight thermal envelope

The building enclosure for this home measures an air leakage rate of 0.8 ACH50, which is extremely low. Minimizing unwanted air movement through the enclosure reduces exfiltration of conditioned air and infiltration of unconditioned air, which reduces energy use for heating, ventilation and air conditioning. Jacobson reports a 90-percent reduction in HVAC operating costs, enabling him to sell up to two-thirds of the onsite energy generation back to the local power companies. The minimized air leakage also provides the added benefit of improved indoor comfort and air quality by controlling moisture and eliminating infiltration of outdoor pollutants and allergens.

SDI Insulation, Inc., a well-known Northern California based insulation contractor, completed all spray polyurethane foam installations in the home, using Accella Bayseal open-cell spray foam on the underside of the roof panels. They also applied Accella Bayseal closed-cell spray foam to the outside of the exterior walls, providing extra R-value, air sealing and structural strength, while creating a rain screen behind the exterior cladding system.

The air-tightness of the exterior walls also minimizes transmission of outdoor noise into the home, while the open-cell spray foam used inside the home’s interior walls reduces sound transfer between rooms.

"We install spray foam insulation in a number of high-performance homes and structures and know the power of the material in maximizing energy efficiency," said Steve DeLorenzi, principal and owner of SDI Insulation. “The Jacobson home, however, showcases how well spray foam complements energy generation technologies such as solar, to create a total energy solution for the home, which in this case is Net Zero Energy.”

The Jacobson House and SDI Insulation were recently recognized with a 2018 Industry Excellence Award, winning first prize in the Residential Wall category. The annual awards program recognizes best-in-class spray polyurethane foam projects in insulation, roofing and specialty applications, and is hosted by the Spray Polyurethane Foam Alliance (SPFA), the technical and educational resource to the spray foam industry.

“The SPFA has been a major proponent of the Zero Net Energy movement for quite some time now, as spray foam technology is particularly well suited for ZNE structures,” added Riesenberg. “We are really proud to witness the growing activity among our members and the industry at-large in Zero Net Energy homes, and we expect to see more and more ZNE projects built in the coming years that will capitalize on spray foam's unique multitude of performance deliverables.”

About the Author

Rick Duncan, Ph.D., P.E is the Technical Director of the Spray Polyurethane Foam Alliance (SPFA), the industry’s leading organization representing contractors, material and equipment manufacturers, distributors and industry consultants. The SPFA promotes best practices in the installation of spray foam and offers a Professional Certification Program to all those involved in the installation of the product.


Author: by Rick Duncan, Ph.D., P.E

Breaking Down the Benefits of Building Energy Codes

Mon, 2018-04-23 19:18
Building CodesBuilding ScienceEnergy Efficiency

Justin Koscher, president of the Polyisocyanurate Insulation Manufacturer’s Association (PIMA), authored an article published in the April 2018 issue of interface magazine.  “Beyond Savings: Building Energy Codes Drive Important Benefits to States and Cities,” Koscher argues that building energy codes can, “deliver a multitude of benefits that can improve the communities within which energy-efficient buildings sit or the lives of the occupants to use these buildings each day.”

The article takes a close look at the many benefits of energy codes beyond energy efficiency and the resulting cost savings. Click here to view the full article.

Author: by Sean Shields

Continuous Insulation Solves Energy Code Math Problem

Mon, 2018-04-23 18:54
Building CodesBuilding ScienceEnergy Efficiency

It is an easy mistake to make. For example, when one comes across the R 13 + 7.5 ci wall insulation requirement in the International Energy Conservation Code (IECC) commercial provisions, it can be tempting to just add the two R-values and install R-20.5 rated insulation in the cavity with the assumption being that the same performance can be achieved with fewer steps. However, by employing just R-20.5 cavity insulation, one would be accepting a 16 percent decrease in thermal performance in a wood-framed wall, or a 40 percent decrease in a steel stud wall, when compared to the energy code requirement.

Continuous insulation (ci) and cavity insulation products are both sold with R-value ratings, but the way these two products are used in wall construction means they do not have the same effectiveness. (The article assumes design according to U.S. energy codes. However, the concepts presented here are applicable in all territories, as the underlying science does not change.) Cavity insulation is interrupted by framing members, which let heat through the insulation layer. On the other hand, ci, as the name suggests, is uninterrupted (except at fasteners and service openings, as defined by IECC). So a layer of cavity insulation is less effective than a layer of ci of the same R-value.

Figure 1: A cross-section of two walls. On the left is the R-20.5 + 0 continuous insulation (ci) wall, and the R-13 + 7.5 ci wall is on the right.

This can easily be seen with thermal modeling software. Figure 1 shows a cross-section of two walls. The left wall is the R-20.5 + 0 ci, and the right is R-13 + 7.5 ci. When these two are subjected to a temperature differential—such as winter outside and room temperature inside—heat flows through the wall from the warm to the cold side. Figure 2 shows the temperature flux, or rate of change, through these walls. As one can see, there is high flux through the wall studs. In the wall without ci, the studs act like a ‘heat highway,’ allowing heat an easy route around the cavity insulation—out of the wall in cold climates and into the wall in hot regions. When ci is added, the highway ends, and heat is forced to slowly seep through the last layer of insulation.

Figure 2: Thermal modeling reveals there is high temperature flux through the wall studs.

The real math problem of determining a wall assembly’s overall R-value is not nearly so simple as just adding the nominal R-values of the different insulation components (e.g. R 13 + 7.5 ci = R 20.5). Depending on whether wood or steel framing is being employed, different procedures for calculating the assembly R-value of a wall are laid out in the American Society of Heating, Refrigerating and Air-conditioning Engineers’ (ASHRAE’s) 2017 ASHRAE Handbook–Fundamentals and IECC. This article will discuss both the methods. But first, let us look at some of the terms.

R-values and U-factors
In this article, the u-factor (or C-factor) of a component or an assembly refers to its thermal conductance. A u-factor is given in units as W/m2.K (Btu/h-F-sf). One way of understanding these units is the rate of heat transfer (W) through a material with a given u-factor is proportional to the temperature difference on both sides of the material (K) and the surface area available (m2).

The R-value of a component or assembly is the inverse of its u-factor. The R-value describes an object’s thermal resistivity, and the units for R-value are simply the inverse of the u-factor: K.m2/W (sf-F-h/Btu). Therefore, good conductors have low R-values and high u-factors, and good insulators have high R-values and low u-factors. If one knows the R-value of a layer or an assembly, one can find its u-factor by simply calculating the inverse. R-value and u-factor requirements mentioned in this article are taken from IECC.

While any layer of material can be described by its R-value, U.S. energy codes only refer to the R-values of insulation layers in the prescriptive R-value compliance path. Conversely, while any layer or assembly also has a u-factor, energy codes only discuss the u-factors of entire wall assemblies. When this is done, a capital ‘U’ is used. For the remainder of this article, a capital ‘U’ will be employed when discussing assembly U-factors.

If an R-value and a u-factor are just two sides of the same coin, why would the energy codes include both as separate compliance paths? This is because the R-values of individual components like cavity insulation and ci can be easier to work with and understand than assembly U-factors. Many people can picture an R-13 insulation batt whereas a wall assembly with a U-factor of 0.064 is not an intuitive notion. One must delve into some math to understand what this means.

If there are several unbroken layers of different materials forming a wall assembly, the R-value of the entire assembly can be found simply by adding the layers:


With u-factors, it is not so simple. Since a u-factor is the inverse of an R-value, to find the overall u-factor, one needs the following equation:

1/utotal =1/u1 +1/u2 +1/u3 +…

(Which, by the way, is the exact same equation. Since a material’s R-value is just the inverse of its u-factor, the author just replaced each R-value with the inverse of the u-factor.) Now one can take the inverse of the entire equation to find the overall u-factor:

utotal=1/(1/u1 +1/u2 +1/u3 +…)

As mentioned earlier, this only applies to the part of a wall with unbroken layers, such as the wall cavity. To account for the framing in the wall, a separate u-factor calculation must be done, and then the two u-factors can be combined to get an overall value for the entire assembly. If one tries to do this using R-values, the answer will be wrong. R-values of different heat flow pathways through an assembly cannot be added together, averaged, or area-weighted to get the overall assembly performance.

Energy codes have tried to make compliance possible without doing any math because the math is not intuitive. This is why they have provided tables listing just a required insulation R-value (and in many cases, an accompanying required ci R-value).

How can this be fair or accurate? It is easy to see a wall’s overall rating depends on a lot more than just the insulation. What about the air films, cladding, structural sheathing, framing, and interior finish? Well, it turns out IECC has assumed the following R-values for all of these layers in a wall in commercial construction:

  • exterior air film: R-0.17;
  • cladding: stucco, R-0.08;
  • sheathing: 16 mm (5/8 in.) gypsum, R-0.56;
  • interior finish: 16 mm gypsum, R-0.56; and
  • interior air film: R-0.68.

When one uses these assumptions to compute the overall U-factor for the prescriptive R-value wall assemblies, they match right up with the U-factor requirements. To see this correspondence in action, one needs to go through the approved U-factor calculation procedures.

Good energy code math
For wood walls, the “parallel path” method is appropriate, (see for example, the “R 20.5 + 0 ci” and “R 13 + 7.5” wall assemblies in Figure 1). This method of calculation can be applied to any combination of ci and cavity insulation required for wood-framed construction (whether commercial or residential). The first step is to determine the R-value for each “path” heat can take through the wall. There are two paths—through the framing (studs and headers) and cavity. In Figure 3, the layers for each path and their R-values are listed. The totals are obtained by summing the R-values for each layer in each path.

Figure 3: A list of the layers for each path heat can take through the walls and their R-values.

One can see while both walls have the same cavity path R-value, the R 13 + 7.5 ci wall has a higher R-value for the framing path (even with a smaller thermal contribution from the thinner 2 x 4 wall framing), thanks to the ci.

The next step is to combine the R-values of the two paths to get an overall value for the entire wall assembly. To do this, the author assumes the wall assemblies are 25 percent framing (21 percent studs and 4 percent headers) and 75 percent cavity by area, which is typical for 406 mm (16 in.) o.c. framing. Then the U-factor for each wall can be obtained with the following formula:

U=ffframing*1/Rframing +ffcavity*1/Rcavity

where ff is the framing factor (25 percent for framing and 75 percent for cavity). Once the U-factor is found, the assembly R-value is just the inverse of the U-factor. This calculation gives us the assembly U-factors and R-values found in
Figure 4.

Figure 4: The U-factors and R-values for the wall assemblies.

Clearly, with complete energy code math, an R 20.5 + 0 ci wall (effective R-16.393) is not equivalent to an R 13 + 7.5 ci wall (effective R-19.608). Further, it becomes obvious the R 20.5 + 0 ci wall complies with and slightly exceeds the R-value requirements only in climate zone five for IECC residential provisions. On the other hand, the R 13 + 7.5 ci wall complies in climate zones up to seven. It is easy to see the location of the insulation makes a big difference (cavity vs. continuous).

Since the math is covered, let us explore a few more comparisons. For instance, how much cavity insulation would one need to achieve performance equivalent to an R 13 + 7.5 ci wall? As demonstrated in Figure 5, R-24 cavity insulation would be required. In most cases, this would require using 2 x 8 studs, since cavity insulation greater than R-21 is generally thicker than the cavity in a 2 x 6 wall. By using ci, the wall is kept to half the thickness it would be otherwise, saving lots of valuable interior floor space.

Figure 5: An R-24 cavity insulation would be needed to achieve performance equivalent to an R13 + 7.5 ci wall.

The benefits of ci ought to be clear for timber-framed structures, but for cold-formed steel framing, the impact is even more significant. Steel conducts heat more efficiently than wood, so the thermal bridging effect is much more pronounced. In this type of structure, ci is absolutely necessary for adequate performance. The calculation method provided in IECC for commercial steel-framed walls is arguably simpler to implement than the parallel path method for wood walls.

Essentially, the code treats the cavity/stud layer of the wall assembly as a single layer with its own R-value, and provides a correction factor to compute the appropriate R-value. For example, in climate zone six, IECC commercial provisions require a wall u-factor of 0.064 or less. The correction factor for climate zone six with steel studs at 406 mm (16 in.) o.c. is 0.46. Another way of saying this is a layer of ci contributes only 46 percent of the listed R-value to the overall wall performance. Consider the two qualifying walls in Figure 6. The advantage of ci over cavity insulation is more obvious in steel-framed walls. In this comparison, adding just R-2.5 of ci more than makes up for removing cavity insulation worth R-5. With deeper 152- and 203-mm (6- and 8-in.) steel studs, the disparity only grows. The full list of correction factors is shown in Figure 7.

Figure 6: The advantage of ci over cavity insulation is more obvious in steel-framed walls. Adding just R-2.5 of ci more than makes up for removing cavity insulation worth R-5.

Figure 7: A list of correction factors.

Though there are many choices when it comes to ci products, polyisocyanurate (or simply polyiso) stands out for its high R-value per inch of 6 (or more, when layers 76 mm (3 in.) or thicker are used). Polyiso ci is available in thicknesses from 6.35 to 114 mm (¼ to 4.5 in.) or more. For the R-7.5 ci requirement, just over an inch of polyiso would be needed. An additional incentive is most polyiso is sold with a foil facer on one or both sides. This is important as polyiso ci can serve as an air- and water-resistive barrier, saving labor and materials costs, if the facer is properly taped, sealed, and integrated with flashing at penetrations. Additionally, polyiso is manufactured without the use of global-warming-causing blowing agents, making it an attractive choice. Thus a wall using polyiso ci can achieve the code-required, minimum R-value with thinner materials than other ci products, thereby providing more saleable floor space.

If one would like to further explore proper wall design for thermal behavior, visit the wall calculator developed by the Applied Building Technology Group.  (Visit for the wall calculator.) This tool uses the approach the authors have outlined to compute the effective R-value and U-factor of a wood-framed wall, and depending on climate zone, determines whether the wall is code-compliant. Additionally, the calculator handles moisture code compliance, another tricky area in design. A version of the calculator for steel walls taking the same approach is in the works.

Timothy Ahrenholz is a special projects engineer with the Applied Building Technology Group. In this role, he develops design solutions for foam sheathing products. Ahrenholz has been involved with standards development and code change proposals for the I-codes and the National Building Code of Canada (NBC). He holds a master’s degree in civil engineering with a structural focus from the University of Illinois, and bachelor’s degrees in physics and mathematics from Covenant College. He can be reached at




SBCA Categories: Energy EfficiencyPerformanceMoisture ControlThermal BridgingAuthor: Timothy Ahrenholz

Can Wood have Better Thermal Performance Than Insulation?

Mon, 2018-04-16 22:07
Energy Efficiency

It’s only been a few weeks since we learned of plans to build a bridge in California using concrete that has been infused with nanocrystals from wood.

Research can be a slow process, at times even tedious. Publication of results often seems to be just as slow. That’s why there is often a time lag between publication of papers dealing with any one particular topic.

And that’s why I was surprised recently when another example of wood-based nanotechnology of interest to the construction industry popped up on my screen. This latest one is at least as intriguing as the first one was.

If you’re interested in insulation, you may be surprised to learn that researchers have found that by stripping away all the filler material in wood, leaving just their fibres, the resulting “nanowood” material outperforms just about all existing insulation. Wood, it seems, might be the new Styrofoam.

A research team at the University of Maryland developed this new nanowood simply by exposing wood to three simple, cheap chemicals: sodium hydroxide, sodium sulfite and hydrogen peroxide. The team discovered these substances strip out the cell walls in wood (which are made up of lignin and hemicellulose), leaving behind just the skeletal nanofibres of cellulose.

It seems the unusual properties of the resulting nanowood can be attributed to the fact that these nanofibres are mostly parallel to one another. And the solid filler material in wood that will usually convey heat is gone, replaced by air. Poorly conducting air.

As well, the parallel alignment of fibres dissipates any heat that does penetrate. It can’t become concentrated.

During lab tests, the research team found the substance’s capacity to keep heat from penetrating from one side to the other is on par with Styrofoam, which is hundreds of times better at blocking heat than wool, glass or epoxy. The team also found that the nanowood is extremely strong, withstanding loads as high as 13 megapascals. That’s the equivalent to almost 2,000 pounds per square inch.

The sample researchers tested was small — just 15 centimetres long and two centimetres thick — but they say it could be made in virtually any size or shape. Because the material is so versatile, it could be used to insulate a wide range of things, from entire buildings to very small computing components.

Since it is extremely light, it could be used where weight is important: aircraft engines, or cars, even spaceships.

And it’s cheap.

Liangbing Hu, who led the research team, says just seven dollars’ worth of chemicals would be enough to make a square metre of nanowood.

There is also an important ecological benefit because it’s made from ordinary, recyclable wood. For its experiments, the team used American basswood, but Hu says any wood would do.

“Wood stores rather than emits carbon dioxide,” he says.

Jeffrey Youngblood is a professor of materials engineering at Purdue University. He was involved in the research involving cellulosic nanocrystals for the concrete to be used in the California bridge this year. But his research interests are focused on the production of any industrially useful products derived from wood.

Referring to the work done at the University of Maryland by Hu and his team, Youngblood says it “really shows that nature has outperformed humankind, once again.

“We just have to unlock the secrets.”

With proper treatment, he says, “wood can become stronger and more insulating than commonly used insulation, such as fibreglass for houses.”

The research paper published by Hu and his team makes prominent mention of nanowood’s biodegradability, its high mechanical strength and the ease of manufacture. In fact, Hu has already spun off a company called Inventwood to commercialize the product.


Author: Korky Koroluk

Homebuilders Outline Opposition to 3 Code Proposals

Mon, 2018-04-16 21:47
Building Codes

The International Code Council (ICC) is preparing for 10 days of hearings on the first batch of proposals to amend the 2021 edition of the building and energy codes.

The good news: NAHB Construction, Codes and Standards committee members and staff are already on the job, preparing the building industry’s arguments to support safe, sensible code changes and jettison proposals that add money, time or materials to building practices that are not cost-effective, benefit product manufacturers more than their customers, or generally won’t work as advertised.

Last month, members of the NAHB Proposal Oversight Group pored over the more than 1,300 proposals submitted for consideration at the ICC Committee Action Hearings, which take place in Columbus, Ohio April 15-25.

The members are particularly concerned about three suggested amendments that would add to the cost of construction without an accompanying benefit to the health and safety of the home owner – the stakeholders NAHB represents when they testify at these hearings.

F267 Part 1 and 2: These proposals both require that four-story or higher buildings of combustible (e.g., wood frame) construction have gypsum board or other noncombustible materials installed during construction on all but the highest two floors when portions of the building exceed 40 feet.

This would typically require gypsum board to be installed on wood-frame construction as stories are being added to the building and potentially before the roof is installed.

S.22. This proposal requires electrical components, appliances, equipment and systems covered by the National Electrical Code to be inspected by a “special inspector.”

If accepted, this proposal would apply to all buildings built to the International Building Code, including four-story single-family homes. It does not specify when the inspections occur, but would seem to require inspections for both rough-in and finish work.

The cost is not quantified, but likely would add several thousand dollars to the typical multifamily project. Importantly, no evidence is provided to show significant electrical issues in buildings due to lack of “special inspections” above and beyond the building inspections already required.

FS34 and FS 35. These proposals would increase the fire-resistance rating of walls and horizontal assemblies between homes’ dwelling units to a two-hour fire barrier and require walls and floors to meet load-bearing requirements without sheathing.

Builders would need to add more layers of Type “X” gypsum board to change the walls and ceilings from a one-hour to two-hour fire rating. It would increase the cost of constructing load-bearing walls because they would have to structurally support loads without compromise by fire or water damage and without sheathing being part of the structural assembly.


HERS Rating System Growth Good for Continuous Insulation

Mon, 2018-04-16 21:42
Building ScienceEnergy Efficiency

Editor’s Note: The proliferation of HERS rating use is beneficial to the exterior foam sheathing industry as continuous insulation makes achieving higher HERS rating scores much easier.

RESNET announced that 13 builders will be added to the group of over 170 RESNET EnergySmart Builders who have committed to having all their homes rated to RESNET’s stringent energy efficiency standards.

By entering into Memorandums of Understanding with RESNET, the following builders have agreed to market their homes with the RESNET HERS Index Score, an industry-leading standard by which a home’s energy efficiency is measured.

RESNET EnergySmart Builders who have made the “Builder HERS Index commitment” receive representation on the RESNET board and at the national level on issues like home energy tax credits and building energy codes.


How Continuous Insulation Requirements Affect CFS Steel Framing

Mon, 2018-04-16 21:30
Building CodesBuilding ScienceEnergy Efficiency

Big changes in energy code requirements occurred with the 2009 and 2012 International Energy Conservation Code® (IECC) and the ASHRAE Standard 90.1-2013 that followed.

The newest versions of IECC and ASHRAE Standard 90.1 call for one to four inches of exterior continuous insulation depending on the building location by climate zone, even in warmer zones where foam board insulation had not previously been required.

Here’s what these requirements mean for cold-formed steel (CFS) assembly design and field integrations.

CFS framing assembly design

Architects, engineers, and contractors need to understand how to apply foam board insulation products as well as address the installation of cladding through the insulation, extensions for window and door openings, and other installations related to wall assemblies containing exterior insulation. Here’s what to do:

Don’t be quick to change

While the national model energy codes require greater thicknesses of continuous insulation (e.g. solid foam insulation), it may be tempting to choose a framing system that requires less continuous insulation than a CFS system.

But why give up the strength, durability, and other benefits of CFS framing when a variety of CFS wall assemblies meet IECC and ASHRAE 90.1 requirements?

Designers have a range of options. CFS walls vary in terms of claddings, the number of CFS members used in the framing, the thickness of CFS members, and other characteristics. And, a variety of methods to determine a wall assembly’s thermal performance — including new modeling software — exist and are approved for use.

According to the Steel Framing Industry Association (SFIA), many architects and large corporations (e.g. Target, Walmart, etc.) are moving toward conducting building simulations to comply with the energy code. This approach, known as the simulated compliance or performance path, allows trade-offs of one component of the energy system for other parts.

Understand how to calculate thermal performance

In general, energy codes and standards call for three ways to determine a wall assembly’s thermal properties:

  • Prescriptive R-value. When a code specifies a prescriptive R-value, you compare the R-values of the wall cavity insulation and the exterior continuous insulation. The wall insulation R-value total must be equal to or greater than the R-values listed in the code.
  • Prescriptive U-factor. Some energy codes specify a U-factor for the entire wall assembly, rather than an R-value just for the insulation. In this case, the designer could check published tables of U-factors for common CFS wall assemblies with a variety of combinations of insulation. The Steel Framing Alliance guide, “Thermal Design and Code Compliance for Cold-Formed Steel Walls, 2015 Edition,” includes U-factor tables for a variety of CFS wall assemblies.
  • Performance pathways. IECC and ASHRAE 90.1 include performance pathways that require building simulations. These new pathways include the total building performance option, energy cost budget method, and the Standard 90.1 Appendix G performance rating method. COMcheck software from the U.S. Department of Energy can help determine if a design meets the IECC and ASHRAE 90.1 requirements.

Field integrations

Energy code compliance will generally require adjustments in how CFS assemblies are installed. This could include the application of energy efficient framing methods such as a two-stud corner versus a three-stud corner, different framing methods for window and door openings, and the framing factor (e.g., 24 inches on center framing versus 19.2 or 16 inches on center).

Attaching continuous insulation materials

Attaching foam board insulation to an exterior brings the surface of those materials further from the face of the framing. The fasteners used will have to resist greater bending forces, since they must cantilever farther to support the exterior cladding, and the soft nonstructural continuous insulation provides little to no support of the fastener or cladding.

The SFIA paper, “Impact of Energy Code Changes,” indicates that this is a critical design issue with heavy cladding materials on multi-story buildings that could threaten occupants or visitors walking below if not designed and installed properly.

Attaching exterior items

Whereas windows, doors, and light fixtures would normally attach to CFS framing, attachment points may not be directly accessible with foam insulation in place.

Therefore, pay extra attention to certain issues: the corners when attaching cladding, jamb extensions for exterior doors, supplemental framing to attach window flanges, and possible changes to the fastening system.

Adjusting the interior space

The requirements to add foam board insulation to CFS and wood-framed assemblies can reduce a building’s interior square footage. The exterior walls may be thicker than other types of framing systems. If there’s no room to expand the envelope footprint, then any added wall depth will have to come from the interior space.

What do the new energy code requirements mean for CFS assembly design and field integrations? They mean doing some thermal calculations and modifying some installation procedures. Of course, what you decide to do in the end depends on your specific state or jurisdiction’s energy code requirements.


Insulation Key in Largest U.S. Passive House Building

Mon, 2018-04-16 21:25
Energy Efficiency

Hillcrest Residences has become the largest confirmed Passive House Institute U.S. certified (PHIUS) development in North America by square footage and number of units, according to a release from the developer.

The new, energy-efficient senior housing development brings 66 apartment homes and community space to Pittsburgh’s Carrick neighborhood. Hillcrest was developed and is owned by The Community Builders (TCB), a leading nonprofit developer of affordable and mixed-income housing. 

The voluntary PHIUS process adheres to rigorous energy efficiency standards that reduce a building’s ecological footprint and results in ultra-low operating costs, requiring little energy for heating or cooling. According to RDL Architects, Passive House developments in the Pennsylvania climate zone on average consume 86 percent less energy on heating and 46 percent less energy for cooling compared with code-compliant buildings.  

Passive House standards are performance-based. At Hillcrest, those standards were achieved by using highly efficient heat pumps in combination with energy recovery ventilation units. 

Construction is air-tight and highly-insulated, keeping the building temperature regulated for residents despite extreme weather. The high levels of insulation and triple-glazed windows help keep the building quiet despite busy, main street traffic. 

In addition, filtered air-exchange systems maintain high indoor air quality aiding against indoor pollutants.

A longtime partner in the city, TCB owns and/or manages 401 housing units in Pittsburgh. Significant funding for Hillcrest’s $15.8M total development cost came from Pittsburgh’s Urban Redevelopment Authority.

Best Practices for Storing and Handling Polyiso Foam

Mon, 2018-04-16 21:07
Energy Efficiency

With the snow finally melting off many roofs and spring ready to pop, here are key considerations about the storage and handling of polyiso roof insulation on a jobsite.


Polyiso insulation is typically shipped protected by a plastic wrap, plastic bag or both. This factory packaging is intended for handling the polyiso in the manufacturing plant and during transit; it should not be relied upon as protection at jobsites or other outdoor storage locations unless specified otherwise by the manufacturer.

Material delivery should be carefully coordinated with the roof application schedule to minimize outdoor storage. When short-term outdoor storage is necessary, whether at grade or on the roof deck, the following precautions should be observed:

  • Bundles should be stored flat above the ground utilizing included feet or on raised pallets. If possible, the bundles should be placed on a finished surface such as gravel, pavement, or concrete rather than on dirt or grass.
  • Unless specified otherwise by the manufacturer, cover the package and pallet with a waterproof cover, and secure to prevent wind displacement.

Note: Polyiso insulation is fully cured and fit for installation upon delivery. No additional storage time is required.


Exercise care during handling of polyiso insulation to prevent breaking or crushing of the square edges and surfaces. Remove the polyiso bundles from trucks with proper equipment. Other means of mishandling, such as pushing pallets off the edge of the truck or “rolling” the pallet across the roof deck, must be avoided.

Product Application

Polyiso should always be installed on dry, clean roof decks in dry conditions. Follow the manufacturer’s recommendations regarding product application to ensure performance to the intended design life of the roofing system. Apply only as much polyiso roof insulation as can be covered by completed roofing the same day.

Construction Traffic

Avoid excessive traffic during roof construction of or on a completed roof surface. Although polyiso has been designed to withstand limited foot traffic, protection from damage by construction traffic and/or abuse is extremely important. Roof surface protection such as plywood should be used in areas where storage and staging are planned and heavy or repeated traffic is anticipated during or after installation.

Some designers and membrane manufacturers specify the use of coverboards as a means of protecting the insulation. If specified, installers should ensure that the coverboard used is compatible with all components of the roofing system, is acceptable to the membrane manufacturer, and meets specified fire, wind and code requirements.

Polyiso roof insulation, like other roofing materials, requires a proper understanding of storage, handling and application to result in a properly constructed roof system. You can find additional technical information about polyiso roof and wall insulation at


Atlas Roofing Develops Online Wall Building Calculator

Mon, 2018-04-16 21:03
Building CodesBuilding Science

Atlas Roofing Corporation has created the EnergyShield® Wall Builder Tool, an industry resource designed for contractors and architects seeking guidance on designing with polyiso wall insulation. The EnergyShield Wall Builder Tool is hosted on the Atlas Roof & Wall Insulation website and allows any user to virtually construct a wall layer by layer.  As each layer is chosen, the user can see the wall rendering as it is assembled. Once the user has created a final product, the rendering of the wall assembly becomes available for download, along with the matching specifications and submittal materials.

The EnergyShield Wall Builder incorporates all EnergyShield products, including EnergyShield Pro, a foil faced polyiso continuous insulation product for commercial exterior walls. EnergyShield® Pro meets all commercial building requirements: NFPA 285 compliance, Class A flame spread, and a thin wall profile of 4” thickness or less. In addition, EnergyShield Pro meets NFPA 286 requirements for exposed interior use. EnergyShield Pro allows for short term savings and long-term energy efficiencies, incorporating an integrated weather and air barrier.

“The EnergyShield Wall Builder Tool was created to speed up the design and submittal process, while helping facilitate creative freedom in building design,” said Tom Robertson, Business Unit Manager for Atlas EnergyShield. “By having millions of possible wall material combinations at their fingertips, architects can more easily envision the possibilities.”

Innovation and Design Freedom for Architects

The EnergyShield Wall Builder Tool grew out of the desire to simplify the building process for customers. Atlas was inspired by similar virtual tools in other industries, like the car builders seen on many automakers’ websites. The Atlas tool gives customers the ability to see their wall as they construct it based on the specific needs of their project, then have the specs and a custom rendering instantly delivered to their email.

The EnergyShield Wall Builder Tool was custom-built from hundreds of digital renderings of wall assemblies and is capable of producing millions of finished combinations. Please visit Atlas® online at to use the EnergyShield Wall Builder.


Atlas Roofing Corporation is an innovative, customer-oriented manufacturer of residential and commercial building materials. Atlas has grown from a single roofing shingle manufacturing facility in 1982 into an industry leader with 24 facilities in North America and worldwide product distribution. All Atlas products are manufactured in state-of-the-art facilities and shipped worldwide from its network of manufacturing plants and distribution facilities in the United States, Mexico and Canada. Atlas Roofing Corporation is made up of 4 major divisions: Roof & Wall Insulation, Shingles & Underlayments, Expanded Polystyrene and Web Technologies. See more at:

Understanding Fire Safe Use of Foam Sheathing

Tue, 2018-04-10 11:18
Building CodesBuilding ScienceEnergy Efficiency

The Grenfell Tower tragedy was the worst building fire in London in recent memory. There have also been many concerns about fire safety and regulatory compliance at Grenfell Tower, including the lack of a working fire alarm system or sprinklers. With multiple fatalities and accusations of neglect, it is no surprise the accident investigation has turned into a full-blown criminal investigation. A key question being asked: “Given all the concerns surrounding the Grenfell fire, does this event reflect code compliant performance in a way that should cause significant regulatory changes for construction in the U.S.?”  

One emotionally-driven concern involves the performance of foam plastic insulated sheathing (FPIS) with different types of cladding. It is worth taking a specific look at both the extent of cladding options available with FPIS and the important restrictions to their use. Strictly keeping to the International Building Code (IBC) can help keep builders and designers from both overreacting to a tragedy like the Grenfell Tower fire and from perpetuating unsafe practices.

Related Content: Post Grenfell, Do You Know the Code and Your Cladding Options?

Additionally, the Foam Sheathing Committee (FSC) of the American Chemistry Council (ACC) has created the flyer below (click on the image to view a larger version) to summarize key concepts for builders, designers and building officials to consider.

Everyone involved in building construction is focused on providing as many safe and code compliant options to the market as possible. This generally results in the best engineered, economic and regulatory compliant solutions for any given project. If we allow emotion to drive decision making and take away generally accepted engineering practice, the easy solution becomes concrete buildings with concrete contents. It’s important to remain focused on avoiding such unintended consequences.



AttachmentSize FSC FIPS Fire Flyer233.11 KB Author: Kirk Grundahl

Builder Details How They Approach Effective Air Sealing

Mon, 2018-04-09 21:59
Building Science

In recent years, airtightness has become an increasingly important area of focus in residential construction. As of the 2012 International Energy Conservation Code (the “energy code” that underpins Chapter 4 of the IRC), builders must attain a minimum blower-door reading of 3 ACH50. However, our company’s goal is to meet or exceed the Passive House level of airtightness, which is 0.60 ACH50.

Many builders think that achieving an airtightness number this low requires a significant increase in budget due to costly materials and increased labor. But on the 1,100-square-foot home shown here, we were able to reach our initial goals with an extremely tight budget of $155 per square foot—which, for our typical practices and our market, is very low. We accomplished it by properly managing our materials and their installation.

Consulting Builder Program

When our clients initially approached us about building a responsibly sized and durable home for their small family, they had concerns about meeting their tight budget and building a high-performance home. In cases like this, my firm institutes our consulting builder program, where I consult with the clients or the project’s architect (or both) during the design phase to make meeting the performance and durability goals easier. The clients pay a consulting fee only if they decide to go with another construction firm. Otherwise, if the clients decide to hire my company, I simply absorb the fee into the construction price for the home. This process lets me build a relationship with clients before they have chosen a builder. More importantly, I no longer have to try to retrofit details like air-sealing into an existing design.

The architects with whom we work are open to designing more-energy-efficient homes and to having a builder involved in the design process. I can’t emphasize this enough: The one, simple step of being involved at the start of the design process is the single most important factor in our ability to remain profitable building high-performance homes. It has advanced both my firm’s budget management process and our ability to hit energy goals.

Our basic airtightness protocol is founded on our ability to develop air-sealing details that can be repeated easily and become part of our “universal” building toolbox. They have to be simple and cost-effective, and they must rely on methods that can be performed by any of our carpenters with materials from a well-stocked lumber supplier.


Sealing down low. Stack effect—the movement of heated air from the bottom to the top of a house on a cold day—tends to draw air into a home at the base, making air leaks low on the house among the most important to seal. The author’s crew accomplishes this in multiple ways. Before the slab is poured, all penetrations are sealed to the sub-slab poly, and the author keeps stub-ups separate so they can be sealed effectively (multiple stubs are nearly impossible to seal well).

Air-Sealing Starts at the Slab

The air barrier starts below ground level, under the building. Our first line of defense is 10-mil poly, which we apply directly over the under-slab insulation. We’ve found that the 10-mil thickness withstands traffic better than the code-required 6-mil and prevents damage that would require us to go back and make repairs. During the installation of the 10-mil poly, all the seams are lapped and taped to ensure an airtight installation. When it’s available, we prefer to use one continuous piece of poly.

While it’s not too likely that we will develop air leaks through the slab penetrations, we instruct our subs that each individual stub through the slab be taped to the 10-mil poly below the slab. This means each line that penetrates the slab does so alone and is not mated with a handful of other pipes—clusters of pipes are nearly impossible to air seal. By separating the stubs by just a couple of inches, however, we are able to properly seal them.


Tim Healey: The wall-to-foundation seal is applied over and under the “sill seal” (which mostly functions as capillary break) as well as at the base of the wall sheathing.

On this home, code required a 3-inch PVC line from below the slab to the roof for a passive radon vent. This radon line ended up being the only roof penetration. In general, we try to avoid roof penetrations, by using approved air-admittance valves for plumbing vents.

Framing Process

Once we are ready to frame a home, we have a crew meeting about our goals for the next steps of the project and the methods we will use, and we ask for objections or ideas. We do this on every project; it brings every crew member, no matter how green or seasoned, fully into the process. At this time, we assign one crew member to be in charge of all air-sealing, which will take place over multiple days and include various materials. This ensures we never run into “I thought that was someone else’s job.”


The Aarow Building crew leaves window and door openings sheathed for the duration of the framing.


When the frame is complete, they’ll come back, fill in doors they left open for access, and run their initial blower-door test. Note the white spray paint above the door. All temporary nailers are painted white for easy identification so they can be filled prior to the test.

When it comes to sealing the sill plate to the slab, we not only use the standard foam sill sealer required by code as a capillary break below the pressure-treated sill, but we also add two beads of sealant. In the past, we have used Tremco’s acoustical, but on this home, we used Geocel from Proflex. Both products are supposed to have a long service life without curing to a hard finish. This is important, because when things become rigid, they tend to crack, creating leaks.

This home was our first attempt using Geocel. The decision to use it was driven by budget; the Geocel is about half the price of Tremco. Also, Geocel is readily available at our supply house. For the majority of homes we build, though, we prefer to use Tremco because we know that its service life can be more than half a century.

We apply the two beads of sealant before we stand the walls. We apply one bead to the pressure-treated plate near what will be the interior, and then staple the sill sealer on like normal. The second bead of sealant is applied to the concrete slab near the outer edge. Placing the beads on opposing sides of the sill sealer creates a non-direct, “Z”-shaped pathway for air movement.

Each joint in the plates is detailed with enough sealant that it squishes out once pushed into place. If it doesn’t squish, we pull things apart and add more. Each of the foundation bolts also receives a large glob of the sealant, just in case. I have found that stressing the idea that the sealant is continuous is important to achieving our goals.

Zip-Tape Sealing

Now that the walls are standing, we start installing the sheathing. Our homes receive full sheathing using Huber’s Zip System. The seams are then taped according to the manufacturer specs. As with the liquid sealants, one crew member is responsible for all taping and rolling, which means everyone else can move on to other tasks. First, we tape all of the horizontal seams of the sheathing on the project and then all the verticals. This creates a shingled effect on all tape joints that will help to shed water from the tape and down the wall, without making a penetration into the envelope.


Corners are areas where Aarow Building ramps up the taping detail. On inside and outside corners, the crew uses three pieces of tape.


First, a single piece that bridges the joint between the meeting panels, and then, a strip on each side of the first piece. Huber makes a 6-inch tape that could work, but it is a special-order item for the author.

The only aspect of the Huber instructions from which we deviate is the inside and outside corner taping—we use three pieces of tape instead of the recommended one. We install one piece on the corner, bridging both sides, and roll it. Then we install a strip on each edge of the first piece, as insurance. Make sure to roll the first piece before installing the others; otherwise, air can easily become trapped behind all three layers. We started using this practice because it was difficult to run tape in a straight line in corners, and the three pieces ensure full coverage. Huber makes a 6-inch tape that would work perfectly for this; however, our supply house doesn’t stock it and we find it easier to have a method that doesn’t require special-order items that can delay the schedule or be overlooked because they’re not on site.

For this home, we didn’t remove the window or door sheathing during framing, so we could test the envelope before installing the windows. We taped and rolled those openings as if they didn’t exist at this stage.

After all the walls are up, we return to the slab-to-wall connection. On this project, we used FastFlash, a liquid flashing product from Prosoco; I also think the fluid-applied sealer from Huber is a superb product. We chalk a line 1 inch down from the top of the slab as a guide, to avoid applying the product too far down for the siding to properly conceal it. Then we apply the Prosoco FastFlash, bridging from the Zip sheathing down to the foundation (see “Air Seal at Base of Wall,” above).

Flashing the base of the wall requires more attention to detail than anything else discussed so far. It’s messy, you’re often in the mud, and the area is low and hard to see. But it is an important spot. Of all the air leaks, those low and high on the wall draw in the most air due to stack pressure. If you’re going to invest your time on air-sealing, those are the areas to concentrate on.

The wall-to-slab connection is also difficult to detail because the slab concrete is never completely flat or straight. Hence, it requires a lot of added effort to create a solid seal. Keep in mind that leaks here will be impossible to repair after construction is complete, so getting them right the first time is critical.

Sealing the Lid

On this home, the ceiling drywall is part of the air barrier, so we needed to make the transition from the Zip System sheathing to the drywall at the top of the wall. For this transition, we use two different tapes: Zip seam tape and 9-inch Grace Vycor Plus with a split backing. We first tape from the wall sheathing onto the top plate. Depending on the wall height, this may take two runs of the Zip tape.


Continuous air barrier. Air leaks at the top of the wall are sealed with a combination of Zip Tape and Grace Vycor Plus. First, the sheathing is taped to the top plate.


Strips of 9-inch Vycor Plus lap over this tape.



The Vycor Plus strips extend inside. There, they will be taped to strips of OSB that will be installed at the perimeter of the ceiling, forming the air barrier for the lid.

Then we install the Grace Vycor. We leave half of the backing on the tape and let it hang into the building so we can connect to it after we’ve installed the ceiling joists or rafters.

After completing the taping, we finish framing the structure and even install the roof sheathing. We strap the interior ceiling with 1x3 pine to create a channel for wiring. This strapping also helps flatten the ceilings.

Around the exterior walls, we stop the strapping short, and we fill in with ripped 8-inch-by-8-foot strips of AdvanTech subflooring. We now take the Grace tape that we had left hanging, and we roll it onto the top side of the AdvanTech and nail it to the bottom of the rafters, providing continuity in the transition from wall to roof. The combination of the AdvanTech and the strapping gives us an even plane on which to install drywall. It also allows the drywall ceiling to be fastened 16 inches on-center when we are framing 24 inches on-center. The tighter fastening schedule helps to prevent sag in the drywall over time.

At ceiling penetrations, we install blocks of AdvanTech in plane with the strapping. We drill through the blocks for any lines that pass through the ceiling, giving us a good surface to seal to.


Ceiling strapping helps flatten the ceiling - a particularly important detail on this sloped ceiling, which will be raked by daylight from clearstory windows.


At the perimeter of the ceiling, the crew installed strips of OSB. The Vycor installed across the top plates adheres to the top of this OSB and drywall is secured to the bottom to complete the air barrier across the lid.

We attempt to keep as much plumbing, electrical, and HVAC inside the air barrier at all times; however, there are always some things that must penetrate the envelope. To preserve the air barrier, we have developed a system for our subs: They are given spray paint (blue for plumbing, yellow for HVAC, and red for electrical) and are required to mark with their paint any hole they wish to drill.


To avoid subs randomly cutting holes through the envelope, the author asks subcontractors to mark hole locations with spray paint. This AC line-set has been marked yellow by the installer and marked as “approved” with white paint by the author.

Once all of the subs have marked holes, we return with white paint and approve their openings. If a sub drills a hole that we did not approve, they cover the cost of repair—which could be substantial depending on where they drill. We also tell them that each penetration can hold only one item. So on this home, the mini-split units used for conditioning each have four penetrations (two coolant lines, power, and a drain). That may seem like a lot, but air-sealing two pipes in one hole is nearly impossible.

Before the ceiling can be installed, any trades that will need to be above it must perform their work. Again, all holes must be marked and approved and there must be only one item per hole. To keep the trades moving efficiently, we mark all future wall locations on the floor as well as provide laser levels to transfer marks to the ceiling. Many items like gas lines and home electrical runs still have to find their way into the ceiling assembly and any mismarking at this stage will cost a lot to fix.

Because we are using the drywall ceiling as an air barrier, we prefer to install the ceiling in one mass without wall penetrations. The building is engineered to not need interior partition walls; therefore, we can frame the entire envelope and drywall the ceiling before any interior partition walls are installed. This process is key to keeping the system simple and envelope leakage manageable.

Verifying Framing Tightness

As a standard practice, our company executes multiple blower-door tests during the sequence of construction, to progressively identify air leaks as we proceed. We own a blower door, and as a builder of high-performance homes, we believe the blower door is just as important a tool as any of our saws.

Blower-door testing before insulation allows the crew to easily identify leaks in the shell before they get buried.

We performed the first blower-door test on this home once we were done with the sheathing and had installed drywall on the ceiling. This test was done before the door and window rough openings had been cut. We filled in the doors we needed for access, as well as the attic hatch, with Zip System sheathing, taping it in place. This allowed us to test the integrity of the primary air barrier—the taped sheathing and drywall lid. The result was 0.31 ACH50 Pa, roughly one-tenth of the allowable leakage by code in our market. It is equivalent to a cumulative hole less than the size of a business card across the entire envelope. Not a bad start.

Systematic Air Barrier

We now have a system that is continuous from foundation to ceiling and back. We can visually inspect almost any part of the 4,700 square feet of envelope—almost the entire air barrier; only the top plate assembly is inaccessible.

The way we find errors in the air barrier is with the blower-door testing. If the numbers on the blower-door test seem off, we can inspect with the blower door running. Every member of the crew and all of our subtrades have the opportunity to go back and correct a seal along any section of the wall or any penetration. This first test also gives us the ability to compare numbers with the next blower-door test that we perform, after the window installation. That gives us a metric for judging how well we installed the windows and an indication of any possible problems that we should correct.

Set procedures like approving penetrations by trades and assigning one crew member to take responsibility for all air-sealing have made the process of achieving a tight envelope as simple and cost effective as possible, while setting us on the path towards an extremely energy-efficient home.

The next blower-door numbers, after the doors and windows were installed, tested out at 0.9. This number was a bit higher, but that’s to be expected after cutting in all the openings. We expect this number to improve slightly before we are completely done, because there are no more holes to be cut, only finishes.


Author: Jake Bruton

Analyzing DowDuPont’s New Leader’s Short-Term Role

Mon, 2018-04-09 21:38

Editor’s Note: When Andrew Liveris shared he would step down as executive chairman of DowDuPont in April, it was announced that Jeff Fettig, the company’s co-lead independent director, would assume the role as a nonemployee executive chairman. The following article summarizes Fettig’s biggest challenges as he assumes this new role.

Generally, the chair or lead director runs the board and the chief executive runs the company. An executive chair has a potentially confusing foot in both camps, running the board and directly supervising the CEO. In DowDuPont’s case, Jeff Fettig took over on April 1 as “non-employee Executive Chairman”. Not joking. This does however reflect the temporary nature of his real job leading into the coming three-way split – setting the new companies and CEOs up for success.

In general:

  • The CEO is an employee.
  • The chair is not an employee. If the CEO is also the chair, there should be a non-employee lead director.
  • An executive chair is an employee, suggesting the need for a lead director as well.

Thus, “non-employee Executive Chairman” is a contradiction in terms.

Executive onboarding is the key to accelerating success and reducing risk in a new job. People generally fail in new executive roles because of poor fit, poor delivery or poor adjustment to a change down the road. They accelerate success by 1) getting a head start, 2) managing the message, 3) setting direction and building the team and 4) sustaining momentum and delivering results.

In Fettig’s case, his personal risk pales in comparison to the risk to the three new companies. In many respects, his real job is to set up for success the new CEOs of DowDuPont’s three spin-offs: Corteva Agriscience, Specialty Products, and Materials Science. These are going to be brand new corporations with $15B+, $20B+ and $45B+ in revenue on day one. Fettig needs to oversee the set up of three new boards, hopefully following generally accepted practices and roles:

Board Roles:

  • Accountable for governance and oversight (noses in.)
  • Approve strategic, annual operating (P&L, cash flows, balance sheet), future capability, succession, contingency and compensation plans.
  • Advise on everything else (hands out.)

CEO Role:

Accountable for strategic, operating, organization plans/results, culture.

Board Management:

Lead Director/Chair accountable for (“owns”) board management

  • Operations (committees) & board organization.

CEO responsible for board management (“does the work”)

  • Prepare/brief in advance, manage meetings, follow-up.
  • Manage board, group, one-on-one, board two-step (Step 1: Test or consult. Step 2: Sell.)
Author: George Brandt

Video: Duck Dynasty Star Helps Promote Spray Foam

Mon, 2018-04-09 21:01
Energy Efficiency

Si Robertson of Duck Dynasty fame took center stage on location at a residential spray foam project. Si suited up in an SWD Urethane coverall, wielded one of the Energy Assault crew’s AP-2 guns, and started shooting the place up a la Arnold Schwarzenegger in Commando. Of course, no foam ever came out of the gun due to the unfortunate circumstance of Si lacking the “licensed SPF applicator” title in his highly decorated resume – yet it provided some much needed laughter and entertainment for the hardworking Energy Assault crew and the SWD team onsite.

Watch the video to catch Si in action as he explains benefits of spray foam insulation…to the best of his ability.