This CE Center article is no longer eligible for receiving credits.
The design of building enclosures entails some very particular requirements that mandate attention to detail. Specifically, barriers of multiple types are needed to restrict air, water, vapor, and thermal transfer. This usually means that a wall assembly requires multiple products to address each one. An emerging alternative is to use a single product with multiple properties, thus eliminating construction steps and reducing labor and material costs accordingly. To work fully, that means the product or material has to demonstrate proven abilities to resist heat, water, and air movement through it in addition to providing a truly continuous installation in order to assure uninterrupted performance. Such a product exists in spray foam insulation systems that have been tested and proven to provide the multiple levels of protection needed in a single-product application. At the same time, it can allow more design freedom due to the custom, field-applied nature of the system. Hence, it is becoming a popular alternative among architects compared to a reliance on multiple, separate barrier products for air, water, vapor, and thermal transfer.
All images courtesy of Icynene, except as noted
Buildings of all shapes and sizes require exterior enclosures that provide air, water, moisture, and thermal barriers. Spray foam insulation can be used to provide all of these in addition to great thermal insulation properties.
Overview of Spray Foam Insulation
Spray foam insulation products have been successfully used in buildings for decades. Part of their appeal is that in addition to providing excellent thermal insulation capabilities, they can also provide a protective barrier that significantly reduces air leakage, minimizes airborne moisture transfer, and reduces bulk water transport. Since it is sprayed in place, almost monolithically, there are no seams or joints, thus creating a truly continuous layer in roof, floor, and wall assemblies. This continuity can be maintained particularly well in exterior wall continuous insulation designs, where the spray foam can be applied to the outside face of exterior sheathing, not just between the studs. These performance characteristics can not only satisfy building code requirements for weather-resistant barriers, they can also optimize energy efficiency by fully restricting heat flow and air leakage. From a design standpoint, spray foam insulation allows for plenty of architectural options. Unlike rigid board insulation products, it can be sprayed in place to conform completely against virtually any building geometry or shape, including curved and rounded forms.
Common Types of Spray Foam
Typically, spray foam insulation is polyurethane based and referred to as spray polyurethane foam (SPF). As a manufactured product, it can be formulated in different types and in different densities, producing correspondingly different characteristics. For buildings, it is usually classified as one of the following:
- Low-density foam weighs around 0.5 pounds per cubic foot (0.4–0.75 available) when installed. It is typically an open-cell product, which remains somewhat flexible in place and achieves R-values comparable to fibrous insulation on the order of R-3.7 per inch or so. Low-density spray foam is fairly vapor permeable and typically does not qualify as a water barrier. Further, low-density foam can only be used in interior applications, such as filling stud or joist cavities, not for exterior continuous insulation.
- Medium-density foam, as the name implies, is heavier and more rigid than low-density spray foam, coming in at about 2 pounds per cubic foot, or roughly four times heavier than low-density material. Its other defining characteristic is the closed-cell nature of the insulation when mixed. Since it becomes a series of small bubbles (cells) of trapped insulating gas (a blowing agent), the thermal performance is directly enhanced, resulting in a noticeable increase in R-value up to R-7.1 per inch. The makeup of medium-density spray foam also allows it to serve as a full air barrier, according to the Air Barrier Association of America (ABAA). Further, in terms of water vapor permeance, it tests and qualifies as a weather- and water-resistant barrier since very little water vapor passes through it.
Based on the differences between these two types of spray foam, it is clear that medium-density spray foam insulations offer the superior water- and moisture-barrier characteristics, the ability to be used as exterior continuous insulation, and much better thermal performance per inch of thickness. Collectively, this means that medium-density, closed-cell spray foam insulation provides the performance of four products in one: insulation, air barrier, vapor retarder, and water-resistive barrier. This combination of traits means it has the potential to save time and money during construction by eliminating the number of products installed or avoiding the need to cut and fit board-type insulation. Once the building is occupied, it also significantly reduces air leakage, minimizes water and moisture transfer, and optimizes energy efficiency.
Medium-density, closed-cell spray foam insulation can be applied very precisely in a controlled manner to create a very predictable surface behind cladding.
Spray Foam in Exterior Walls
All of these attributes make medium-density, closed-cell insulation suitable for many portions of the building enclosure. However, it is in exterior wall assemblies that it has become particularly popular. When used as continuous insulation over wall sheathing, it not only provides a superior insulation installation, it helps enhance the rest of the wall assembly as well. First, it should be noted that expanding spray foams or low-density foams create the irregular and bulbous forms that many people associate with spray foam insulation. However, medium-density foam is different in that it can be installed fairly precisely and in very controllable thicknesses. That means it creates a smooth and predictable surface that is ready to receive cladding over it.
Installing spray foam insulation is much simpler than installing rigid foam boards, which require fasteners, cutting, and waste. Spray foam has its own adhesive properties that keep it securely attached in place once applied and avoid waste. Of course, not all buildings are designed to be rectilinear, and even those that are often have some unique or irregular conditions along the walls. Rigid insulation boards are necessarily rectilinear and don’t bend or adapt easily to irregular conditions in a wall assembly. Therefore, they may not be a practical or realistic choice for certain buildings. By contrast, spray foam insulation conforms directly to the surface it is being applied to regardless of shape, geometry, or irregularities. That means that it fully covers and seals over the underlying construction to provide a truly continuous, uninterrupted insulation layer and protective barrier. It also means that buildings designed with intentional curves, domes, arches, angles, or other non-rectilinear shapes no longer need to suffer from lower performance because of limitations from other insulation types. For example, a curved surface would be very difficult if not impossible to cover properly with rigid foam board insulation. Mineral fiber batts or blankets do curve and may be used in wall cavities, including curved surfaces. However, they do not provide the same performance in terms of insulation level per inch, water resistance, or air resistance. Spray foam insulation provides excellent performance in all of those areas since its characteristics are not limited or influenced by the shape of the building.
The design of building enclosures entails some very particular requirements that mandate attention to detail. Specifically, barriers of multiple types are needed to restrict air, water, vapor, and thermal transfer. This usually means that a wall assembly requires multiple products to address each one. An emerging alternative is to use a single product with multiple properties, thus eliminating construction steps and reducing labor and material costs accordingly. To work fully, that means the product or material has to demonstrate proven abilities to resist heat, water, and air movement through it in addition to providing a truly continuous installation in order to assure uninterrupted performance. Such a product exists in spray foam insulation systems that have been tested and proven to provide the multiple levels of protection needed in a single-product application. At the same time, it can allow more design freedom due to the custom, field-applied nature of the system. Hence, it is becoming a popular alternative among architects compared to a reliance on multiple, separate barrier products for air, water, vapor, and thermal transfer.
All images courtesy of Icynene, except as noted
Buildings of all shapes and sizes require exterior enclosures that provide air, water, moisture, and thermal barriers. Spray foam insulation can be used to provide all of these in addition to great thermal insulation properties.
Overview of Spray Foam Insulation
Spray foam insulation products have been successfully used in buildings for decades. Part of their appeal is that in addition to providing excellent thermal insulation capabilities, they can also provide a protective barrier that significantly reduces air leakage, minimizes airborne moisture transfer, and reduces bulk water transport. Since it is sprayed in place, almost monolithically, there are no seams or joints, thus creating a truly continuous layer in roof, floor, and wall assemblies. This continuity can be maintained particularly well in exterior wall continuous insulation designs, where the spray foam can be applied to the outside face of exterior sheathing, not just between the studs. These performance characteristics can not only satisfy building code requirements for weather-resistant barriers, they can also optimize energy efficiency by fully restricting heat flow and air leakage. From a design standpoint, spray foam insulation allows for plenty of architectural options. Unlike rigid board insulation products, it can be sprayed in place to conform completely against virtually any building geometry or shape, including curved and rounded forms.
Common Types of Spray Foam
Typically, spray foam insulation is polyurethane based and referred to as spray polyurethane foam (SPF). As a manufactured product, it can be formulated in different types and in different densities, producing correspondingly different characteristics. For buildings, it is usually classified as one of the following:
- Low-density foam weighs around 0.5 pounds per cubic foot (0.4–0.75 available) when installed. It is typically an open-cell product, which remains somewhat flexible in place and achieves R-values comparable to fibrous insulation on the order of R-3.7 per inch or so. Low-density spray foam is fairly vapor permeable and typically does not qualify as a water barrier. Further, low-density foam can only be used in interior applications, such as filling stud or joist cavities, not for exterior continuous insulation.
- Medium-density foam, as the name implies, is heavier and more rigid than low-density spray foam, coming in at about 2 pounds per cubic foot, or roughly four times heavier than low-density material. Its other defining characteristic is the closed-cell nature of the insulation when mixed. Since it becomes a series of small bubbles (cells) of trapped insulating gas (a blowing agent), the thermal performance is directly enhanced, resulting in a noticeable increase in R-value up to R-7.1 per inch. The makeup of medium-density spray foam also allows it to serve as a full air barrier, according to the Air Barrier Association of America (ABAA). Further, in terms of water vapor permeance, it tests and qualifies as a weather- and water-resistant barrier since very little water vapor passes through it.
Based on the differences between these two types of spray foam, it is clear that medium-density spray foam insulations offer the superior water- and moisture-barrier characteristics, the ability to be used as exterior continuous insulation, and much better thermal performance per inch of thickness. Collectively, this means that medium-density, closed-cell spray foam insulation provides the performance of four products in one: insulation, air barrier, vapor retarder, and water-resistive barrier. This combination of traits means it has the potential to save time and money during construction by eliminating the number of products installed or avoiding the need to cut and fit board-type insulation. Once the building is occupied, it also significantly reduces air leakage, minimizes water and moisture transfer, and optimizes energy efficiency.
Medium-density, closed-cell spray foam insulation can be applied very precisely in a controlled manner to create a very predictable surface behind cladding.
Spray Foam in Exterior Walls
All of these attributes make medium-density, closed-cell insulation suitable for many portions of the building enclosure. However, it is in exterior wall assemblies that it has become particularly popular. When used as continuous insulation over wall sheathing, it not only provides a superior insulation installation, it helps enhance the rest of the wall assembly as well. First, it should be noted that expanding spray foams or low-density foams create the irregular and bulbous forms that many people associate with spray foam insulation. However, medium-density foam is different in that it can be installed fairly precisely and in very controllable thicknesses. That means it creates a smooth and predictable surface that is ready to receive cladding over it.
Installing spray foam insulation is much simpler than installing rigid foam boards, which require fasteners, cutting, and waste. Spray foam has its own adhesive properties that keep it securely attached in place once applied and avoid waste. Of course, not all buildings are designed to be rectilinear, and even those that are often have some unique or irregular conditions along the walls. Rigid insulation boards are necessarily rectilinear and don’t bend or adapt easily to irregular conditions in a wall assembly. Therefore, they may not be a practical or realistic choice for certain buildings. By contrast, spray foam insulation conforms directly to the surface it is being applied to regardless of shape, geometry, or irregularities. That means that it fully covers and seals over the underlying construction to provide a truly continuous, uninterrupted insulation layer and protective barrier. It also means that buildings designed with intentional curves, domes, arches, angles, or other non-rectilinear shapes no longer need to suffer from lower performance because of limitations from other insulation types. For example, a curved surface would be very difficult if not impossible to cover properly with rigid foam board insulation. Mineral fiber batts or blankets do curve and may be used in wall cavities, including curved surfaces. However, they do not provide the same performance in terms of insulation level per inch, water resistance, or air resistance. Spray foam insulation provides excellent performance in all of those areas since its characteristics are not limited or influenced by the shape of the building.
Wall Assembly Integration
Of course, the method of securing and attaching cladding material needs to be acknowledged. Connectors or anchors for attaching cladding, whether for thin systems such as metal or fiber cement or thicker systems such as ties for brick and masonry, can be a factor in the wall assembly. Rigid foam boards are commonly available in 2-foot widths for the purpose of fitting above and below, such connectors or anchors that are spaced 2 feet apart vertically. Often, that means that there can be a horizontal gap along the joints of the foam boards, which compromises the full insulating performance of the system. This can be exacerbated if there are unusual details or irregular shapes along the wall, which alter the spacing of the cladding connectors and result in imprecise field cutting of the insulation. Spray foam insulation, on the other hand, covers and seals around all connectors and attachments completely. There is also greater flexibility with regard to attachment placement and configuration since a slightly bent or misaligned anchor can still be sprayed around without requiring realignment. This all minimizes the disruption in the continuity of the insulation, reducing it to only the actual thickness of the attachment materials.
Medium-density, closed-cell spray foam insulation adheres to substrates and seals completely around cladding anchors, such as brick ties and other penetrations.
Overall, medium-density spray foam covers the wall construction completely and creates a much more uniform layer of continuous insulation and barrier against air and weather. In the process, it seals completely around cladding attachments as well as covers over all of the joints and seams of substrates, such as exterior gypsum board. When applied around windows and doors, it makes smooth, continuous, and well-sealed transitions at heads, sills, and jambs, while conforming to flashings and other transition membrane components. If the walls have curved or other non-rectilinear shapes, the on-site spray application is ideal in that it can conform to any shape or feature of the wall system. Finally, manufacturers have recognized the need to demonstrate fire resistance and have successfully tested medium-density, closed-cell insulation in wall assemblies as part of showing code compliance for fire ratings.
Thermal Resistance
Spray foam products are most commonly known for their insulating properties, which is appropriate since they provide an excellent solution for insulating buildings thoroughly and completely. In buildings that use framed exterior walls constructed of either metal or wood studs, it is common to think in terms of insulating between the studs. But each of those studs is a break in the insulation that collectively can reduce the thermal performance of the wall by 20, 30, or even 50 percent. This is because the studs and other elements no longer have the thermal resistance of the insulation but instead act as a thermal bridge, allowing heat to flow more freely between inside and outside. Add in the thermal bridges that occur along floor lines or around major structural elements, such as columns, beams, piers, etc., and it is clear that a truly energy-efficient building needs a different approach to insulation.
Based on the above, the principle of continuous insulation in the building enclosure has been adopted in building codes, voluntary standards, and best practices. In exterior wall systems, that typically means a layer of exterior continuous insulation is installed outside of the exterior wall sheathing such that it covers over the outer surface of everything behind that sheathing too—the studs, the floors, the structure, etc. This dramatically increases the effective thermal performance of a wall since all or most thermal bridging is eliminated. Furthermore, the temperature of the framed wall and structure can approach the temperature of the living space if the right amount (thickness) of continuous insulation is used. That means that during cold outdoor conditions, most or all of the wall will be not only warm, but more likely to remain dry since condensation will not likely occur. During hot outdoor conditions, a majority of the wall will be dry and cool. Such environmental conditions translate into a wall under less long-term temperature and moisture stress, which leads to greater more durability and longevity of the wall.
Vapor Barriers
There is an additional benefit of having full exterior continuous insulation using closed-cell foam, particularly in cold climates. The codes recognize that insulated walls need an interior vapor barrier/retarder to prevent warm, moist air from entering into the wall assembly, condensing, and causing the potential for damage, rot, mold, or other issues. The type of vapor retarder required or prohibited by the code is based on the climate zone where the building is located and the classification listed in the codes based on perm ratings and material. The lower the perm rating, the less water vapor that passes through the material. The code classifies vapor retarders as follows (per 2015 International Building Code [IBC] Section 1405).
- Class I vapor retarders have a very low perm rating of less than or equal to 0.1 and include materials such as sheet polyethylene or non-perforated aluminum foil.
- Class II vapor retarders have a moderate perm rating greater than 0.1 but less than or equal to 1.0, as found in kraft-paper-faced fiberglass batts or certain vapor-barrier-tested paints and closed-cell spray foam insulation.
- Class III vapor retarders have a higher perm rating of greater than 1.0 but less than or equal to 10.0 and are common of most latex or enamel paints.
Low-permeability spray foam is recognized by building codes to have vapor-barrier qualities that can reduce the need for other interior vapor retarders.
The code goes on to say that there are exceptions to the otherwise required Class I or Class II vapor retarder in colder climates. One of those is the use of minimum R-value levels (based on climate zone) of continuous insulation on the outside of a framed wall. Further, it specifically states that “only Class III vapor retarders shall be used on the interior side of frame walls where foam plastic insulating sheathing with a perm rating of less than 1 is applied…on the exterior side of the frame wall,” (2015 IBC Section 1405.3.2). Note that in this code section, medium-density SPF is considered equivalent to foam plastic insulating sheathing and also applies here. In essence, this language is saying that there is no need, in fact there might be harm, in using a higher-rated Class I or Class II vapor retarder in walls that have foam insulation that already provides that attribute. Since medium-density, closed-cell spray foam insulation applied on the outside (or inside) of the exterior sheathing meets this criteria, there is no need for anything but common latex paint or the equivalent on the inside, finished surface of the wall. This not only means that there is less concern about moisture condensation inside the wall assembly, it also means that the wall has more potential to dry out quickly in the event any wayward moisture does make it there since wall drying is permitted both to the interior and exterior.
Water and Moisture Control
Exterior wall cladding materials (whether masonry, metal, composites, or others) typically do not completely prevent moisture or rainwater from entering into a wall. Some cladding materials are porous, while those that aren’t commonly have seams or joints that are limited in their ability to keep out water. In fact, some systems, which are commonly referred to as rainscreen cladding systems, are specifically designed to allow water to enter behind the cladding and drain harmlessly away out of the bottom. While this is good for the cladding, it may not be good for the rest of the wall if it isn’t properly treated. That is why building codes require a weather-resistive barrier behind cladding to protect the integrity of the rest of the assembly and prevent degradation of building materials due to rust, corrosion, rot, etc. In practice, this barrier really ends up needing to resist water, and spray foams are tested on their ability to function as a water-resistive barrier. For purposes of this article, while we are addressing both water and air infiltration resistance, we will stay with the insulation-testing definition of “water-resistant barrier,” abbreviated as WRB.
A number of sheet, roll, and spray-on products have been developed to provide the requisite performance of a WRB. Each of those products have their own limitations, including their own seams or joints, the need for a separate construction step, and the ability to be compatible with other wall materials and products.
SPF as a Water-Resistant Barrier
Medium-density, closed-cell spray foam products have been tested as WRBs and demonstrated that they are capable of shedding water and limiting moisture intrusion. Many such products have been evaluated according to the code requirements and criteria for WRBs, and are officially designated as water-resistive barriers accordingly. Since there are no joints to tape or overlapping practices to maintain, water-barrier performance is more easily assured on the construction site with spray foam insulation since it forms a continuous layer. In this case, not only is exterior continuous insulation provided, but water that penetrates past the cladding system and is forced by pressure toward the interior meets the spray foam’s exterior surface. The water-resistive nature of the medium-density spray foam is such that this water will drain down along the surface and not continue progressing into the wall assembly where it could cause damage. Such a moisture control system is particularly important to have in coastal or high-precipitation areas where driving rain is common.
Of course, the exterior wall needs to be designed to ensure that this water is actually diverted back outside of the cladding. This is usually accomplished by following an exit path and flashing system incorporated at strategic points in the wall assembly. For example, the typical path that driving rain would take in a masonry veneer cladding over a metal framed wall would be for the water to make its way to a drainage plane on the inside of the masonry or the face of a WRB spray foam surface.
The air gap between the inner brick surface and the outer spray foam surface is important to maintain since that is what allows unimpeded drainage to occur. The water will collect and fall along this surface to the bottom of the air gap where it needs to run toward weep holes and exit out of the wall. This flow needs to be maintained or designed at all variations in wall construction too, such as floor slabs or wall offsets. The key is that all of the components, including the cladding, the drainage plane, the drainage gap, and the exit, are coordinated and work together to assure proper functioning.
A cross section through a typical brick veneer wall indicates that the air gap between the brick cladding and the WRB layer of continuous insulation needs to be designed to allow water to flow down and out of the assembly.
Flashing Details
The other important area to address is wall openings, such as windows and doors. Typically, flashing of some sort is required around these openings to assure that water doesn’t penetrate behind the window or door frame. Integration of medium-density spray foam products with flashing membranes is a key component of the water-resistive-barrier system therefore. Fortunately, it is easy to find flashing that is compatible with spray foam insulation. Further, in order to become a certified installer, many spray foam insulation contractors are required to receive training in applying both flashing and spray foam successfully in the field. In addition, some manufacturers have tested the compatibility of self-adhering and liquid-applied membrane products with their medium-density, closed-cell spray foam products and can advise design professionals on compatibility.
Details above windows and doors need to rely on integrated flashing to direct water out of the wall assembly and avoid potential damage.
Other Considerations
It is certainly possible to provide continuous insulation in exterior walls using extruded polystyrene (XPS) or other rigid insulation board products. However, those may require a separate water-resistant barrier, which may or may not double as an air barrier and may create a vapor barrier where one is not needed. Further, they typically require transitional materials at all openings that may or may not be easy to integrate with the board type of insulation.
The choice of cladding may influence the choice of insulation/WRB behind it as well. Brick and masonry veneer walls in particular are known to require careful attention to water drainage and flashing. Failure to do so in design and construction can lead to degradation and even failure of the masonry, particularly in locations where freezing temperatures are common. Stone veneer has the same concerns, particularly if the stone is very porous. Other cladding systems may have more or less porosity as a material, but their seams and joints remain a point of concern. In general, the safest route to take is to be sure that the WRB is foolproof to install, complete in its ability to seal, and continuous across all exterior wall features.
Air Sealing
In addition to sealing out water and moisture, medium-density spray foam products also have the benefit of creating a continuous air-barrier layer in one product. This means that outdoor air seeping past the cladding system will come against a barrier, preventing it from moving further within the wall. This is quite significant since unwanted air infiltration is as important as thermal resistance, if not more so, in determining the energy efficiency of the wall. Energy codes have recognized this phenomenon and now contain mandatory provisions to properly address air sealing of wall assemblies.
Testing of Air Barriers
Recognizing a need to properly define and understand the technical aspects of effective air barriers, the ABAA has become the resource for the design and construction industry on this topic. It points out that an air-barrier system is a combination of building components within the building enclosure—
designed, installed, and integrated in such a manner as to stop the uncontrolled flow of air into and out of the building enclosure. It further indicates that effective air barriers have positive impacts not only on heating and cooling costs, but also on moisture problems, indoor air quality, and acoustics. That is because moving air can carry unwanted moisture, contaminants, or noise into a building. Overall, proper air sealing with an air-barrier system results in more sustainable and durable buildings that address numerous green design issues.
ABAA also tests air-barrier materials, which it defines based on a tested air-permeance value. To be a qualifying air-barrier material, the air permeance must be equal to or less than 0.004 cubic feet of air per minute per square foot of material when tested at an air pressure of 1.57 pounds per square foot. The testing basis for this qualification is ASTM E2178: Standard Test Method for Air Permeance of Building Materials. Most foam insulation, particularly if it is closed cell, qualifies as an air-barrier material. Keep in mind, of course, that this test determines the amount of air permeance that migrates through tested materials. It does not address field conditions of holes or gaps in the material. Therefore, ABAA also conducts tests to determine what qualifies as a full air-barrier assembly based on ASTM E2357: Standard Test Method for Determining Air Leakage of Air Barrier Assemblies. In this case, it is not just a single product, but the total air-barrier system (i.e., material, attachment method, joint/seam treatment, etc.) that must demonstrate performance as a continuous air barrier. Further, under this test, it must also perform as a liquid drainage plane (i.e., WRB), accommodate movements of building materials, and provide connections to adjacent materials to prevent air leakage at all critical locations. In short, this second test tries to replicate fully installed conditions.
Large areas of exterior walls can be covered with a continuous, joint-free layer of spray foam insulation.
Among the many rigid foam insulation boards that exist in the marketplace, only four have currently received the ABAA air-barrier-assembly designation. However, in order to qualify, these products typically require sealants or tape to be applied at all joints and penetrations, which can be a very labor-intensive process. Furthermore, the sealing tends to get applied on the exterior, which is the most challenging location in terms of temperature and humidity changes, not to mention quality control of the work being performed. By contrast, virtually all medium-density spray foam products that have been tested have been found to be air impermeable. The thickness where this characteristic is achieved is typically 1.5 inches or less depending on the specific product used. For an exterior continuous insulation application, medium-density spray foam products have the advantage of creating a continuous insulation layer, a water-resistant barrier, plus an air-barrier layer all in one step. With no joints to tape or seal, airtight performance becomes much easier to deliver. This is notably true around wall penetrations for mechanical, electrical, plumbing, or other components that are traditional weak points among conventional air barriers. The one-step application process can also generate cost and construction schedule savings compared to the multiple steps of taping, sealing, and filling encountered with other systems.
Material Compatibility
Part of the testing for a full air-barrier assembly requires manufacturers to prove that materials are chemically and adhesively compatible with adjacent materials proposed for use. Those adjacent materials include flashings and membranes commonly found at wall openings, such as windows and doors, or at wall transitions, such as the base of a masonry wall with weep holes. As a result, the transition materials/membranes that are compatible with a particular spray foam manufacturer are also commonly identified by that manufacturer, although they may be made by others. Collectively, the proper use and detailing of spray foam insulation with appropriate transition membranes creates a complete, effective, and durable air-barrier system. Construction details have been developed by manufacturers to guide architects on how to best accomplish the air-barrier assembly using spray foam products.
Indoor Environmental Quality
When looking at green building design, there are more categories than just energy efficiency. One significant criteria is the ability to create a positive and healthy indoor environment for people. That means not only providing appropriate levels of ventilation, light, and views, but it also means eliminating the exposure of people to materials or chemicals that could be detrimental to human health. In that regard, there has been some extensive work done to identify and eliminate unhealthy chemicals or compounds from building materials. There have also been some misperceptions and misunderstandings about some products and materials, including spray foam insulation. Some applications of spray foam in residences have been blamed for causing unhealthy reactions due to the chemical makeup of the blowing agents, although that is not a universal issue. Nonetheless, the manufacturers of these products have responded appropriately and changed the formulation of most spray foam to comply with indoor environmental quality standards.
Reducing VOCs
One of the main concerns with any building product is the presence of volatile organic compounds (VOCs). These have been prevalent in everything from plywood to furniture to paint, and manufacturers have been working hard for decades to find suitable replacements while still maintaining product quality. The same is true for spray foam insulation. While all are addressing this, at least one manufacturer has achieved the creation of some ultra-low-VOC-level products. This has been independently verified based on protocols and procedures developed by a task group of the American Chemistry Council’s Center for the Polyurethane Industry (ACC CPI). Its conclusion, after extensive research, testing, and evaluation, is that the health concerns of these products are reduced dramatically such that the amount of time recommended for re-entry after a building has been insulated and appropriately ventilated is reduced to only an hour. For occupied residences, the re-occupancy time is reduced to 2 hours.
Continuous spray foam insulation in exterior walls not only addresses energy efficiency and construction durability, but also can help safeguard indoor environmental quality by reducing the possibility of mold.
Reducing Mold
There is another significant benefit from using spray foam insulation related to indoor environmental quality. As already noted, when used as exterior continuous wall insulation, closed-cell spray foam also prevents air, water, and moisture penetration. That produces a wall system and framing that should be drier and less likely to be subject to rot or deterioration. A drier condition also takes away one of the necessary ingredients for mold, namely moisture. For wood-framed wall systems in particular, this means a notably decreased chance of mold growth to occur in the wall. Mold remediation has become a significant concern in many buildings because it has been shown to have direct and serious links to things like asthma, allergies, and other health issues. Therefore, designing wall systems to reduce the possibility of mold is not only positive for human health, in many cases, it is necessary for risk management to ward off potential lawsuits for damages over improper design or construction.
Conclusion
When medium-density, closed-cell spray foam is applied as exterior continuous insulation, it also has the properties of a continuous water-resistive barrier, air barrier, and vapor retarder all in one product application. Further, a properly designed wall assembly, using this material will assure not only code compliance, but a better sealed installation that will keep out unwanted water and air in the assembly, while still allowing any trapped moisture to dry to the interior. These characteristics make it an attractive, easy to install, continuous barrier system that will improve energy efficiency, durability, indoor environmental quality, and overall sustainability in the buildings that it is used in.
Peter J. Arsenault, FAIA, NCARB, LEED AP, is a practicing architect, sustainable building consultant, continuing education presenter, and prolific author engaged nationwide in advancing better building performance through design.
www.linkedin.com/in/pjaarch
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Icynene-Lapolla is a leader of high performance building material innovations aimed at optimizing the building envelope and maximizing energy efficiency. Available in more than 31 countries, Icynene-Lapolla is a global manufacturer and supplier of spray polyurethane foam for insulation and roofing applications, reflective roof coatings and equipment. Serving architects, builders, contractors and homeowners, Icynene-Lapolla’s solutions enhance residential and commercial structures, in both new and retrofit construction. www.icynene.com
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