Energy Efficiency and Building Science News

BFS and BMC Announce Planned $11.2B Merger

Thu, 2020-08-27 08:46
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

Tue, 2020-08-25 12:14
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



Designing and Installing Exterior Foam Correctly

Mon, 2020-08-24 17:14
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

Mon, 2020-08-24 16:38
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:  


A Cost Benefit Analysis of Energy Efficient Buildings

Mon, 2020-08-24 16:28
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

Mon, 2020-08-24 16:11
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

Mon, 2020-08-24 16:03
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

Mon, 2020-08-24 15:58
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

Mon, 2020-08-24 15:53
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

Mon, 2020-08-24 15:46
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.


Version 3 of Steel and Wood Wall Design Calculators Released

Thu, 2020-07-23 16:33
Energy EfficiencyBuilding Science

The Applied Building Technology Group has recently released updated versions of both the Steel Frame Wall Calculator and Wood Frame Wall Calcuator. These tools help coordinate thermal insulation energy code compliance and water vapor control building code compliance for a proposed steel frame or wood frame wall assembly on a commercial or residential building.

Both calculators, now at Version 3.0.0, include additional building and energy code options. They also now allow the user to download a PDF of the calculator output, making it easy to email, print or include with other specification documentation.


Presentation Highlights Need for Moisture Management Changes

Thu, 2020-07-23 16:18
Building Science

At the recent IIBEC 2020 Virtual International Convention and Trade Show, Jay H. Crandell, P.E. gave a presentation titled “Applying Recent Building and Energy Code Advancements for Durable and Energy-Efficient Building Enclosures". In the presentation, Crandell highlighted and explained the code advancements while providing guidance and examples of their effective application for design and construction of code-compliant, durable, and energy-efficient building enclosures.

Photo Credit: EverGuard Solar

Energy codes have advanced in recent years—in large part by requiring more efficient building thermal enclosures. This advancement typically requires more insulation or a more strategic and effective use of insulation, such as continuous insulation on exterior walls. Regardless of the insulation methods and materials used for compliance, this change has altered how water vapor and bulk water must be managed to maintain or even improve durability.

Consequently, long-standing building code “rules” for moisture management are no longer reliable or, at best, are rendered incomplete. Fortunately, very recent building code advancements for water vapor control, including some related improvements for bulk water management, have answered this call to better coordinate with the prior energy code advancements.

To view or download the slides from the presentation, visit


ASHRAE Releases Buiding Science Guide for Reopening Schools

Thu, 2020-07-23 15:57
Building Science

The ASHRAE Epidemic Task Force has developed guidance on the operation of HVAC systems to help mitigate the airborne transmission of SARS-CoV-2 as schools prepare to reopen for the fall academic year.

The 41-page Presentation includes convenient checklists to prepare educational buildings to resume occupancy such as starting up HVAC systems as well as checks and verifications to maintain during the academic school year. The guidance is meant to provide practical information to school districts and university campus environmental health managers, facility managers, administrators, technicians and service providers.

“As schools prepare to reopen for the fall academic semester, it's important to keep children and school staff safe,” said 2020-21 ASHRAE President Charles E. Gulledge III, P.E. “ASHRAE’s school reopening guide will serve as a resource to school leaders as they work in lockstep with health experts to finalize plans to keep everyone safe.”

The guide includes the following topics:

  • Determining Building Readiness
  • Equipment & System Specific Checks & Verifications During the Academic Year
  • New/Modified Facility Design Recommendations
  • Filtration Upgrades
  • Operations of Occupied Facilities
  • Controlling Infection Outbreak in School Facilities
  • Higher Education Facilities Recommendations

 Also included is guidance formulated to help designers retrofit and plan for the improvement of indoor air quality and to slow the transmission of viruses via the HVAC systems as well as new guidance on student health facilities, laboratories, athletic facilities, residence halls, and large assemblies, lectures and theatres.

“School and university officials are challenged with making very difficult decisions on how to best protect both students and staff as education facilities reopen, said Corey Metzger, ASHRAE Epidemic Task Force Schools Team lead. “This guidance offers a solid framework on ventilation control, filtration and maintenance that can be applied to different climate zones, building types and HVAC systems.”

For the complete ASHRAE Epidemic Task Force school reopening guide and other COVID-19 resources, visit


DuPont Develops Next Generation of Syrofoam

Thu, 2020-07-23 15:39
Building Science

In support of its commitment to reduce greenhouse gas (GHG) emissions while driving sustainable innovation, DuPont™ has announced the phased launch of a new, reduced global warming potential (GWP) Styrofoam™ Brand Insulation. Beginning January 1, 2021, the Styrofoam™ Brand Insulation family of products will include lower GWP options, advancing DuPont’s 2030 Sustainability Goals and complying with adopted and upcoming state and provincial hydrofluorocarbon (HFC) regulations throughout the United States and Canada. Building on the company’s previous announcement, the multi-phased approach will deliver GHG reductions in support of the Paris Climate Agreement along a timeline that is more aggressive than the Kigali Amendment to the Montreal Protocol.

“The new, reduced GWP product will first launch in Canada and U.S. states that have adopted 2021 HFC regulations as of April 1, 2020, with plans to expand the product offering going forward.”

“We are committed to leading the transition to more sustainable buildings, while ensuring our products continue to deliver the high level of performance our customers trust,” said Tim Lacey, Global Vice President & General Manager, DuPont Performance Building Solutions. “Pairing market performance needs with innovation that addresses environmental challenges, such as climate change, is at the core of our beliefs.”

This latest innovation from DuPont represents the next step forward in the evolution of the Styrofoam™ Brand franchise, introduced nearly 80 years ago. Styrofoam™ Brand Insulation- an extruded polystyrene (XPS) foam insulation- was the first brand in its category. Since its launch, it has played a key role in the building and construction industry, providing thermal, air, and moisture management that contributes to operational building energy efficiency over the lifetime of buildings. With this latest innovation step change, DuPont also expects a reduction in embodied carbon to be reflected in an updated Environmental Product Declaration (EPD), which will be available with the new products.

“We are taking a thoughtful, phased approach to launching this latest Styrofoam™ innovation to ensure we are providing a sustainable, code-approved solution that does not sacrifice the performance our customers have come to trust,” said Lacey. “The new, reduced GWP product will first launch in Canada and U.S. states that have adopted 2021 HFC regulations as of April 1, 2020, with plans to expand the product offering going forward.”

To learn more about DuPont™ Styrofoam™ Brand Insulation, visit


2019 Group B I-Code Appeal Process Solidifies

Thu, 2020-07-23 15:35
Building Codes

As we reported in January, the Group B 2021 I-Codes contain a number of significant improvements in the realm of energy efficiency and building science.

In March, the ICC reported it had received complaints regarding the online governmental consensus vote and its Validation Committee reviewed a third-party intendent audit of that process and ruled there were no voting irregularities.

In June, the ICC created a webpage tracking the six appeals it had received.

On July 8, the ICC posted the official Notice of Appeals, which outlines the timeline for appeals hearings (which will be announced by August 7), identifies the four-member appeals board, and outlines how interested parties can submit their comments prior to the start of the appeals hearings in last August or early September.

For more information, check out ICC’s 2019 Group B Appeals webpage.


New High Performance Building Website Aimed at Consumers

Thu, 2020-07-23 15:31
Energy EfficiencyBuilding Science

NAHB and the National Association of Realtors have launched a new joint education website, Home Performance Counts, aimed at consumers.  The intention of the website is to help the public better understand the rapidly growing high-performance home marketplace and its benefits.

This site is also intended to help builders and real estate agents better communicate high-performance home features and benefits, as demand continues to rise. They cite the number of these homes certified to the National Green Building Standard® increasing by more than 57% since 2017 as a prime indicator of this growing demand.

Of particular note to the building science community is a section on the page that allows consumers to submit questions to their “Ask the Pros.”  It may be worthwhile periodically accessing this section to see both the questions asked regarding building performance, but also to monitor the answers they post.

Home Performance Counts also offers resources for consumers and builders, including:

 Home Buyers:

  • Education on the qualities and benefits of high-performance homes.
  • Communication tools that highlight tips for discussing with builders and real estate agents using more common terms so that home buyers can ensure they’re getting the home they want.
  • Directories for home builders and REALTORS® in their area.

 Builders and Real Estate Agents:

  • Common language tools to better communicate the value and benefits of high-performance homes to prospective customers.
  • Best practices for positioning their business competitively in the marketplace.
  • Latest trend data and information to stay informed of shifts in the industry.


Connect with CI: Announcing the Launch of our New Social Media Profiles

Wed, 2020-07-15 14:18
Energy EfficiencyBuilding Science

The team at appreciates our community of supporters and are always looking for new ways to put valuable and timely information at your fingertips. We’re excited to announce that in addition to our monthly e-news publication, we’ve also recently launched two new social media profiles on Facebook and LinkedIn. We’ll share information and updates regularly, including valuable articles, building-science-related news, and more!

Please take a moment and visit our pages. Once there, click “Like” or “Follow.” We look forward to bringing you great information and connecting with you! We encourage you to comment on our posts, ask questions and share the content with your friends, family, and co-workers.

Join us on Facebook!

Join us on LinkedIn!

If you’re looking for more information about continuous insulation, but aren’t a social media user, you can always visit or send us a message.


2021 IBC and IRC Adopt Improved Vapor Retarder Requirements

Wed, 2020-07-15 13:34
Energy EfficiencyBuilding Science

In a prior EEBS article, we listed various advancements forthcoming in the 2021 International Energy Conservation Code (IECC), International Building Code (IBC), and International Residential Code (IRC). Last month, we discussed advancements for conventional Portland cement stucco installation requirements to improve moisture-resistant performance in moist climates. As the next installment, this article addresses advancements to the water vapor retarder provisions of the 2021 IBC and IRC.  It is also related to the discussion on cavity and continuous insulation in a companion article which places this topic in the context of improving system-based design and construction guidance in building codes.

To start, the new code language for vapor retarders is shown in Figure 1 (as based on ICC code change proposal RB223-19). This may appear to be a lot to digest, but it is actually pretty straight-forward and effective. To help, a brief explanation of the most significant aspects of this code change follows.

R702.7 Vapor Retarders. Vapor retarder materials shall be classified in accordance with Table R702.7(1). A vapor retarder shall be provided on the interior side of frame walls of the class indicated in Table R702.7(2), including compliance with Table R702.7(3) or Table R702.7(4) where applicable. An approved design using accepted engineering practice for hygrothermal analysis shall be an alternative. The climate zone shall be determined in accordance with Section N1101.7 (R301.1) [ See Figure 1].


  1. Basement walls.
  2. Below-grade portion of any wall.
  3. Construction where accumulation, condensation or freezing of moisture will not damage the materials.
  4. A vapor retarder shall not be required in Climate Zones 1, 2, and 3. [This exception is not in 2021 IBC]

R702.7.1 Spray foam plastic insulation for moisture control with Class II and III vapor retarders. For purposes of compliance with Tables R702.7(3) and R702.7(4), spray foam with a maximum permeance of 1.5 perms at the installed thickness applied to the interior side of wood structural panels, fiberboard, insulating sheathing or gypsum shall be deemed to meet the continuous insulation moisture control requirement in accordance with one of the following conditions:

  1. The spray foam R-value is equal to or greater than the specified continuous insulation R-value.
  2. The combined R-value of the spray foam and continuous insulation is equal to or greater than the specified continuous insulation R-value.
TABLE R702.7(1)




Sheet polyethylene, nonperforated aluminum foil, or other approved materials with a perm rating of less than or equal to 0.1.


Kraft-faced fiberglass batts, vapor retarder paint, or other approved materials applied in accordance with the manufacturer’s installation instructions for a perm rating greater than 0.1 and less than or equal to 1.0.


Latex pain, enamel paint, or other approved materials applied in accordance with the manufacturer’s installation instructions for a perm rating of grater than 1.0 and less than or equal to 10.0.


TABLE R702.7(2)






1, 2

Not Permitted

Not Permitted


3, 4 (except Marine 4)

Not Permitted



Marine 4, 5, 6, 7, 8



See Table R702.7(3)

  1. Class I and II vapor retarders with vapor permeance greater than 1 perm when measured by ASTM E96 water method (Procedure B) shall be allowed on the interior side of any frame wall in all climate zones.
  2. Use of a Class I interior vapor retarder in frame walls with a Class I vapor retarder on the exterior side shall require an approved design.
  3. Where a Class II vapor retarder is used in combination with foam plastic insulating sheathing installed as continuous insulation on the exterior side of frame walls, the continuous insulation shall comply with Table R702.7(4) and the Class II vapor retarder shall have a vapor permeance of greater than 1 perm when measured by ASTM E96 water method (Procedure B).


TABLE R702.7(3)



Marine 4

[or all of 4 for 2021 IBC]

Vented cladding over wood structural panels.

Vented cladding over fiberboard.

Vented cladding over gypsum.

Continuous insulation with R-value ≥ 2.5 over 2 x 4 wall.

Continuous insulation with R-value ≥ 3.75 over 2 x 6 wall.


Vented cladding over wood structural panels.

Vented cladding over fiberboard.

Vented cladding over gypsum.

Continuous insulation with R-value ≥ 5 over 2 x 4 wall.

Continuous insulation with R-value ≥ 7.5 over 2 x 6 wall.


Vented cladding over fiberboard.

Vented cladding over gypsum.

Continuous insulation with R-value ≥ 7.5 over 2 x 4 wall.

Continuous insulation with R-value ≥ 11.25 over 2 x 6 wall.


Continuous insulation with R-value ≥ 10 over 2 x 4 wall.

Continuous insulation with R-value ≥ 15 over 2 x 6 wall.


Continuous insulation with R-value ≥ 12.5 over 2 x 4 wall.

Continuous insulation with R-value ≥ 20 over 2 x 6 wall.

  1. Vented cladding shall include vinyl, polypropylene, or horizontal aluminum siding, or brick veneer with a clear airspace as specified in Table R703.8.4(1), or other approved vented claddings.
  2. The requirements of this table apply only to insulation used to control moisture in order to permit the use of Class III vapor retarders. The insulation materials used to satisfy this option also contribute to but do not supersede the thermal envelope requirements of Chapter 11.


TABLE R702.7(4)




Continuous insulation with R-value ≥ 2.

4, 5, and 6

Continuous insulation with R-value ≥ 3 over 2 x 4 wall.

Continuous insulation with R-value ≥ 5 over 2 x 6 wall.


Continuous insulation with R-value ≥ 5 over 2 x 4 wall.

Continuous insulation with R-value ≥ 7.5 over 2 x 6 wall.


Continuous insulation with R-value ≥ 7.5 over 2 x 4 wall.

Continuous insulation with R-value ≥ 10 over 2 x 6 wall.

  1. The requirements of this table apply only to insulation used to control moisture in order to permit the use of Class II vapor retarders. The insulation materials used to satisfy this option also contribute to but do not supersede the thermal envelope requirements of Chapter 11.

FIGURE 1. New Vapor Retarder Provisions for the 2021 I-Codes (IRC shown)
NOTE: For more options and an automated means of compliance, refer to and the wall calculators found at

Some of the most significant aspects of the new provisions in Figure 1 are explained as follows:

  1. A new format uses a look-up table approach to make it easier to identify all prescriptive requirements applicable to a given climate zone for a given frame wall assembly. For example, Table R702.7(2) is the launching point for determining water vapor retarder requirements and options. Other tables and text provide details for specific conditions of use.
  2. New provisions are provided for use of foam plastic insulating sheathing (continuous insulation) in combination with a Class II vapor retarder such coated Kraft paper facers on fiberglass batt cavity insulation. See footnote ‘c’ in Table R702.7(2) which points to specific requirements in Table R702.7(4). This table compliments existing provisions for use of Class III vapor retarders while maintaining adequate inward drying potential and promoting better alignment with energy code R-value requirements for continuous insulation.
  3. The Class III vapor retarder provisions in Table R702.7(3) are expanded to apply to all of Climate Zone 4, not just Marine 4 (this applies to the 2021 IBC only). Table R702.7(2) also clarifies that Class III vapor retarders are permissible in Climate Zones 1-3 with no special requirements.
  4. The Class III vapor retarder provisions in Climate Zones 7 and 8 are differentiated and strengthened to address an inadvertent error in prior codes that treated Climate Zones 7 and 8 the same.
  5. In footnote ‘b’ of Table R702.7(2), the code specifically addressed the avoidance of so-called “double vapor barrier” walls (i.e., having Class I vapor retarder materials on both sides of the assembly). These types of walls have performed well in some conditions of use such as cold-dry climates with use of appropriate weather protection and application of sufficient exterior continuous insulation. However, there also are many cases where they have not performed well such as moist climates coupled with poor weather protection practices and inappropriate use of interior vapor barrier in warm-humid climates. One way, however, to realize the winter vapor control benefits of a Class I interior vapor retarder while avoiding the low inward drying potential problem is addressed in item 6 below.
  6. The code now recognizes “smart” or responsive vapor retarders for use in any climate zone as shown in footnote ‘a’ of Table R702.7(2). The code defines a responsive vapor retarder as any Class I or II vapor retarder (based on dry-cup water vapor permeance) that also has a water vapor permeance of greater than 1 perm (based on wet-cup water vapor permeance).[1] When used on the interior side as a vapor retarder, they promote inward drying by “opening up” in periods or seasons where inward vapor drives occur (most prominent during spring and summer months). In the winter, they “close up” to restrict water vapor from moving into the assembly when outward vapor drives are the strongest and most persistent.

The other significant consideration is what is still missing from the IRC and IBC water vapor retarder provisions. Most importantly, the code lacks a means of controlling the vapor permeance on the interior and exterior side of wall assemblies that do not include continuous insulation to control water vapor as now addressed more completely in the 2021 codes. For example, the code provisions for continuous insulation in Figure 1 rely on compliance with underlying “insulation ratios” to ensure the inside of the wall does not reach a dew-point or high humidity levels for a sustained period of time and these ratios vary by climate. For walls without continuous insulation, the ratio of permeance of outer and inner layers of the wall must be similarly controlled by use of permeance ratios that also should vary with climate. However, such a methodology remains absent from the code. It is advisable to consider this potential omission carefully to better inform code compliance decisions. For additional information on this matter, refer to ABTG RR No. 1701-01, and the wood wall calculator and steel wall calculator that evaluate and implement insulation ratios and permeance ratios as applicable for walls with cavity insulation only, cavity and continuous insulation, or just continuous insulation. 

[1] Greater than 1 perm wet cup is advisable for hot and humid climates or when combined with low-perm exteriors. This advice is based on two things: (1) coated Kraft paper facers for FG batts are the benchmark conventional responsive vapor retarders and they generally have a wet-cup vapor permeance of about 1.8 perms or more (see ASHRAE Handbook of Fundamentals) and (2) in hot-humid climates studies have suggested a minimum 3 perm for interior finishes to avoid the disaster of having a vapor barrier on the wrong side of the assembly in this climate, like vinyl wall paper – see ABTG RR No. 1410-03). In addition, if used with exterior foam sheathing in colder climates, the requirements of Table R702.7(4) should be applied as a conservative code interpretation.


2019 Group B I-Code Receives Six Appeals

Mon, 2020-06-15 18:19
Building Codes

As we reported in January, the Group B 2021 I-Codes contain a number of significant improvements in the realm of energy efficiency and building science.

In March, the ICC reported it had received complaints regarding the online governmental consensus vote and its Validation Committee reviewed a third-party intendent audit of that process and ruled there were no voting irregularities.

The final step in the process is to review and resolve outstanding appeals.  To that end, ICC has created a webpage tracking the six appeals it has received from:

  1. American Gas Association;
  2. Air Conditioning, Heating & Refrigeration Institute;
  3. Leading Builders of America;
  4. National Association of Homebuilders; and,
  5. Two appeals from Jake Pauls, an independent consultant

ICC staff are currently in the process of correlating where these appeals overlap and coordinating their review of all the appeals received.

For more information, check out ICC’s 2019 Group B Appeals webpage.



2021 I-Code Development Schedule Released

Mon, 2020-06-15 18:15
Energy EfficiencyBuilding Science

While the Group B 2019 I-Code development process may have recently wrapped up (although, there are some appeals still to deal with), there is no rest for the model code community. The ICC recently released its schedule for the development of the 2021 Group A I-Codes and 2022 Group B I-Codes.

Essentially, the 2021 edition of the I-Codes will be published sometime in the fall of 2020 and the deadline for 2021 Group A code change proposals is January 11, 2021. Committee Action Hearings (CAHs) will occur April 11-21, 2021 in Rochester, NY, and public comments will be due July 2, 2021, with Public Comment Hearings (PCHs) September 22-29, 2021 in Pittsburgh, PA.

To see all the dates, click on the pdf link below.

2021-2022 I-Code Development Schedule