Air and vapor barriers can be viewed as unsung heroes, defending a building enclosure and its occupants from poor thermal performance, unhealthy indoor air quality, moisture infiltration, and the problems that occur when moisture collects in the enclosure. A 2017 MASONRY blog post focused on the critical functions of air, water, and vapor barriers play in the building enclosure. How can contractors building MASONRY DESIGN enclosures select the proper air and water barriers to not only meet the architect’s specification but help the enclosure deliver optimal performance? What are some best practices when it comes to installing air, water, and vapor barriers? What support is available to help contractors navigate the tremendous breadth of products available? To address these questions, MASONRY Design magazine spoke with Tiffany Coppock, Commercial Building Specialist at Owens Corning®.
MASONRY DESIGN: Last year’s blog post mentioned that air, water, and vapor barriers should be installed to function as part of an enclosure system. What are some problems that can arise when the enclosure system is not considered?
Tiffany Coppock: It’s vital to have a working knowledge of how air and water barriers work together during the installation process and how other products installed afterward may impact performance. For example, after an air and water barrier is installed in a MASONRY DESIGN wall, its continuous membrane will likely be punctured repeatedly as other components are installed. With that in mind, it’s important to think about the methods used to install materials through the barrier. Are you using a fastener that will require four penetrations per attachment or are you using a single barrel anchor fastener that requires one penetration through the membrane? Does the fastener maintain compression creating a gasket effect for air and water tightness around the membrane? We see a lot of power actuated fasteners, but a common nail or stapler doesn’t necessarily hold in compression over the lifespan of a building. It’s important to consider whether the same level of compression will exist several years down the road.
The chemical compatibility of materials is another consideration. You may have an asphaltic-based flashing system, but your window manufacturer requires a specific sealant to uphold its warranty. A situation could arise where the asphaltic flashing comes into contact with a non-compatible silicone product. Incompatibility can be addressed successfully, but ideally, these considerations will be thought through during the design stage.
MASONRY DESIGN: From a macro-level, how are codes, extreme weather events, and the labor market influencing air and water barriers?
Tiffany Coppock: The original standards for air barriers to pass the ASTM E283, E1677, E2178 or E2357 ASHRAE standards, targeted performance at .4 CFM or lower. The E2357 tests we see these days consider pressures applied from the inside and outside and evaluated how well the product was able to maintain continuity and adherence to the walls and as a system. Today there are a wide range of products – fluid applied, peel-and-stick, self-adhered and rigid board – and the majority of these products will meet ASTM 2357. Now that the building community has proved existing standards are widely achievable, we may see code requirements tightening as has already been demonstrated on USACE projects
A good portion of the innovation was being driven by the government as a building owner and the manufacturing community to improve air and water leakage resistance. As an example, the USACE standards required design designed to ASHRAE 189.1 rather than 90.1 which not only required inspection and commissioning of the building but set forth requirements for air leakage that really inspired efforts to improve air and water barriers and allowed contractors to build better buildings knowing that the building’s performance would be tested. We learned as an industry how to install air and water barriers better and the magnitude of energy savings when we focused more on air and water barriers. The success led to tightening the requirements of the standard by 50%.
As extreme weather puts the spotlight on durability, manufacturers are developing air and water barriers that can withstand long exposure to UV light and adhere faster in a wet environment. Manufacturers are also looking at new ways to apply chemistries. We’re seeing more acrylics changing to silicones or Silyl Terminated Polymers (STPs), and asphaltic materials though they have a long history of strong performance are losing some of their popularity due to concerns about fire and compatibility. The tight labor market is driving companies to develop air and water barriers that do not require the same level of expertise and knowledge to install compared to earlier products. And of course, innovations that can keep products affordable without compromising performance are always a priority for the industry.
MASONRY DESIGN: How have air and water barriers been integrated into LEED?
Tiffany Coppock: As an actual building code requirement, air and water barriers were relatively new a decade ago and initially, LEED did not require air and water barriers based on the ASHRAE version referenced but you could use air barriers to possibly achieve points for building commissioning or energy efficiency. Since then, much attention has focused on air filtration and removing VOCs to support indoor air quality and there have been two versions of air and water barrier requirements for LEED. ASHRAE now requires an air and water barrier be included in the design of buildings… We’re seeing a more holistic approach to building commissioning and various tests such as blower door testing to assess air leakage and whole building testing after the building is complete.
Because air and water barriers help manage the flow of air and vapor into and out of the building, we can better support the building’s mechanical performance, such as specifying properly sized and more efficient air handler units. Collectively, these improvements allow the building to consume less energy, whether electricity, solar or wind.
MASONRY DESIGN: Occupant wellness is a growing subject of interest. How do air, vapor, and water barriers help protect against contaminants such as mold in the enclosure?
Tiffany Coppock: Keeping the building environment dry and ensuring the building has the ability to “dry out” following exposure to any moisture is critical. While vapor barriers are not a holistic solution to protecting against mold, they are one tool in the toolkit. Prior to the development of air barriers, there were weather barriers to prevent liquid water leakage above grade and waterproofing barriers to help manage below grade moisture where hydrostatic pressure was present. The introduction of air barriers restricted the movement of air and liquid moisture throughout the building, but not necessarily the flow of vapor. Today, there are products that stop air, liquid, and vapor and they can be installed in one location within the wall or in multiple locations- i.e. the air, water, and vapor barrier may be a single membrane on the exterior sheathing or an air and water barrier may be installed on the sheathing and the vapor barrier is a separate product installed on the interior behind the gypsum drywall.
The location of the vapor barrier in the building is very important and relates to the physics of moisture and condensation in the enclosure. In a hot, humid environment, moisture driven into the building can create condensation on the interior wall as the temperature of the living space drops and support conditions favorable to mold. A vapor barrier positioned on the outside of the building can forestall vapor from traveling through the wall to a temperature where it would condense and help keep the enclosure dry. An opposite situation arises in a cool climate where winter air is humidified and warm interior air escapes through the walls to the exterior. In that situation, a vapor barrier installed on the warm inside of the wall can guard against the formation of condensation in the wall cavity where spalling and efflorescence could occur on the brick veneer. Proper location is paramount as a vapor barrier positioned in the wrong location can actually contribute to condensation within the building.
Ultimately, the strategy behind a vapor barrier is to stop moisture from reaching a spot in the building where it can condense. Another vapor management strategy would focus on making sure the wall is completely vapor permeable so that condensation vapor travels through the wall to the exterior where it can evaporate into the environment and dry quickly before moisture accumulates.
MASONRY DESIGN: What tools are available to help designers, specifiers, and contractors choose the right product?
Tiffany Coppock: The variety of products can be overwhelming and is one reason Owens Corning® has a building science team devoted to analyzing moisture throughout the enclosure. Basic depoint analysis allows us to look at how moisture travels through a wall under given circumstances including temperature analysis, relative humidity, and specific wall assembly. This data can provide designers with direction to guide the selection of materials and location of the product within the enclosure in a very quick analysis. We can also provide advanced WUFI analysis for mission-critical buildings such as library archives, laboratories, and healthcare facility MRI suites where the environment must be tightly controlled and we cannot afford to have a performance failure. We combine historical weather data, material analysis, and anticipated drying times to lend an even higher degree of guidance to inform material selection and placement within the enclosure.
MASONRY DESIGN: From a contractor’s perspective, what resources are available to help inform the selection of the right air, water, and vapor barrier product?
Tiffany Coppock: The number of choices for stopping air, water, and vapor has definitely made the selection process more challenging. Today, every product on the market seems to be an air barrier. There’s a running joke in the community that peanut butter actually makes a great air barrier (passing ASTM E2357), albeit bringing pest control issues! But when making a choice, it’s key to consider which product is going to deliver longevity and be compatible with other components in the system. Familiarity with a product and how it is installed can also support the choice of barrier product, as well as access to the type of equipment necessary to apply the barrier to the substrate.
Contractors shouldn’t hesitate to ask a product’s manufacturer to come out and provide training on installation as well as guidelines for various steps such as fastening patterns and detailing. Another great resource is the Air Barrier Association of America (ABAA). ABAA provides training for various assembly types (peel and stick, rigid board, etc.) and most recently wall systems such as the Owens Corning® Cavity Complete® system. Certification includes classroom instruction, on-site demonstrations, written exams, and practical exams, along with a card noting certification. Increasingly, we are seeing more specifications require installation by an ABAA certified installer along with ABAA certified projects. Such certification provides a third-party audit that speaks to a contractor’s knowledge and demonstrated proficiency with a building enclosure product.
MASONRY DESIGN: From an installation perspective, what are some best practices for installing air and water barriers?
Tiffany Coppock: The installation practices actually begin in the design development stage. It’s a good idea to gather drawing sets, stick a pen on the air and water vapor and actually trace all the way around the building. Assuring continuity is critical AND if the pen has to be picked up at any point, it’s a good indication that the particular area needs to be closely analyzed for potential air and water leakage.
Water barriers must be continuous and contractors should evaluate continuity when they receive the drawing set. Contractors should also look for compatibility and ensure substrates are correct. For example, if you’re applying a barrier to a CMU wall, you want to make sure there aren’t a lot of mortar fins that could interfere with consistent application of the product. Frequent meetings with team members and sub-contractors can make sure everyone understands how important the materials are to the finished building. Protecting the air barrier after it is installed is imperative. For example, if a product is not supposed to be exposed to UV light over a period of time, installation should be timed appropriately. Be sure to protect the product from any freezing, thawing, vehicular or mechanical damage that could occur, as damage is a primary reason for contractor callbacks. As a matter of fact, the ability to repair damage should also factor into product selection- some membranes are easier to restore to a continuous state than others.
MASONRY DESIGN: What are some questions or considerations to take into account when selecting an air and water barrier product?
Tiffany Coppock: There are many factors to consider, but here are some big questions to ask. First, is it code compliant? Make sure the product complies with all specifications and codes before placing the product order. Next, consider the installation procedures for applying the air and water barrier to the wall and protecting its following installation. Also, know the minimum and maximum temperature for application, humidity levels, etc. Of course, the cost is always a factor. Consider not just the cost of the product but the labor cost associated and how that cost may vary according to geographic region. In some regions of the country, one product may be more expensive to purchase but deliver a lower overall installation cost based on labor rates.
It sounds obvious, but be sure the roof is installed before applying the air and water barrier. I’ve been in buildings where water was ankle deep and the air barrier was already applied. These barriers are not intended for immersion in water. The walls will only hold water for so long and it’s important to protect the area from moisture before and following application.
Consider how the shape of the structure lends itself to various methods of application. I’ve worked on a number of sphere shaped buildings and their unique geometry often makes a fluid applied membrane the simplest type of barrier to installing.
It should be noted that while these barrier products are dealing with air and water movement throughout the enclosure, they must also comply with NFPA 285 in most commercial situations. The Owens Corning® Enclosure Solutions NFPA identifies almost 75 different products categorized by vapor permeable or impermeable and application method that comply with NFPA 285 and provides details for helping select a product that works with the building design and wall assembly.
And finally, don’t hesitate to ask for help. The Owens Corning Building Science Center offers moisture analysis, NFPA 285 assembly design resources, and regional guidance through all phases of design.