This article was contributed by Henri Fennell, a building envelope specialist and architect from North Thetford, VT with over forty years of experience in energy conservation design, products, and services. Henri was one of the featured presenters at our recent IAQ & Energy 2018 Conference. We encourage Informer readers to visit Henri’s website for more information and resources on spray foam installations. www.polyurethanefoamconsulting.com. Videos of Henri’s presentations at IAQ & Energy are available at www.iaqandenergy.com.
So, why have there been so many foam problems in recent years?
First, “so many” is still a small percent of the foam projects performed every year in this country. Of the nearly two billion pounds of polyurethane foam used each year in the US for construction, foam quality problems occur in less than 2% of the installations. Why they occur is not an easy question to answer, as the answer must of necessity include pointing to the large number of possible causes that exist throughout the construction industry.
Lack of Industry Standards
Despite the steady increase in the use of foam in the US over the last ten years, there are still no comprehensive US foam installation standards to provide guidelines or oversight for this segment of the polyurethane foam industry. A uniform system for product and installer certifications should be part of the standards when they are in place, but the industry has needed an industry-accepted certification program with an enforcement component for over thirty years. Only organizations like The Air Barrier Association of America (ABAA) provide for-fee quality assurance programs for projects that include spray foam, and the only certifications available are provided by an assortment of industry members, including equipment manufacturers, foam suppliers, and various training organizations with many levels of varying sophistication and competency. The Spray Polyurethane Foam Alliance (SPFA) has recently launched a training program, but this program focuses primarily on the installation (after the gun), allowing the processing portion of the on-site manufacturing (after the gun) to rely solely on the processing equipment to produce a quality product. Unfortunately, about 80% of the failures I work on are due to improper processing, and not due to improper installation. Certifications provided by industry members are not consistent, often only including sections of the planning and installation work related to the training providers’ interests; i.e., equipment manufacturers train only about how to use their equipment, material manufacturers train only about how to install (not process) their chemicals, and OSHA trainers focus on installer safety. Incidentally, they never train about occupant safety. Additionally, some distributors provide good service, equipment, and sometimes even have training programs equal to the SPFA program, but some only sell the lowest cost materials to anyone who wants to buy. Currently, it is left up to architects and consumers to regulate and mandate the minimum quality and performance requirements for foam installed in their projects. Their three choices are: 1. Develop specifications and standards foam projects 2. Hire an experienced, competent installer 3. Hire a third-party foam expert (Commissioning agent) to oversee the foam installation
Lack of experience with foam in the design industry
Understanding material choices and the building science implications of how foam products are integrated into the building enclosure requires a thorough comprehension of the physical properties of these materials, and the related building science. Product selection and detailing are key to the success and performance of the enclosure assemblies. These materials require more submittals than are normally required for most manufactured products. In order to assure a quality product and installation, architects must verify that the minimum documentation is available for the installer to manufacture the product on site, and they must also be capable of approving the post-work (close-out) submittals that verify that processing and installation requirements have been met. This isn’t because most foam products aren’t well designed and thoroughly tested, but because they are manufactured on site, and not in a controlled-environment facility. I can make this point by stating that I have had more foam problem clients with installations done in cold weather, than during the summer. This lack of experience with foam technology extends to code officials and inspectors as well. Building officials have to be able to inspect and approve every building product used in modern construction. Polyurethane foam is one of the most complex products to learn about because it is site manufactured and new products are introduced on a frequent basis. Unfortunately, many officials aren’t qualified to know what to look for in product quality and installation technique. I have a training program about spray foam for code officials that is a 4-hour program, and it could easily be longer. I have only provided this program in three eastern states, even though I have offered it in all of the eastern states.
To complicate matters for new installers, there are many new foam products with all of the obligatory claims about green, energy performance, and productivity attributes. The use of these new foam systems always have learning curves for the installers, many of whom are still learning to process the tried and true established systems. For example, I recently inspected a project where the installer was doing his first project, a $500,000 contract for a large, high-profile museum addition. The installer was installing a new-to-the-market product, could not get his brand new equipment to work, and the technicians had no experience in the actual spray process. This was, in fact, their first spray foam job. This is a case in point for how choosing the least expensive product and installer can result in an installation problem.
So, why haven’t there been more foam problems lately?
In short, industry-standard equipment is well designed and is generally reliable. Its shortcoming is in the lack of accurate feedback provided to the installer about the machine’s performance. Most important, the equipment does not turn itself off in the event that one of the processing parameters are not being met. There are numerous technical reasons why this is important, but suffice it to say that if the machines had fault-protection capabilities about 85% of foam failures would be prevented. This capability would nearly eliminate the one-figure percent failure rate.
Training and Certification
Given all of the issues I’ve touched on above that need to be understood to be a qualified foam installer, what about the new entries into the foam installation market? Most new installers who haven’t worked for years with experienced installers, haven’t had a chance to learn about the materials, installation, and building science related to the work they are going to perform. They can’t just buy a foam rig and be effective in this industry, at least, not for long. Foam installers are actually manufacturing a product at the construction site. Most construction products are manufactured in a controlled-environment factory using equipment that typically costs at least an order of magnitude more than their equipment. Key to preventing foam problems is for foam installers to have an understanding of how to reliably process the material given the equipment and protocols available. The slowdown in the construction industry has encouraged many existing insulation contractors (glass fiber, cellulose, etc.) and other installers in previously unrelated trades (masonry, paint, dampproofing, carpentry, etc.) to diversify into installing field-applied foam and air/vapor (A/V) barrier coatings. While new foam installers historically have been experienced first or second tier technicians who leave an established foam installation company and start their own business, the recent dramatic growth in the number of spray foam and sealant contractors has included a significant number of contractors from other trades or people seeking new career paths with little or no experience in foam processing, and many who lack experience in construction in general. In addition, most new entries into the foam industry do not have a comprehensive working knowledge of the building science related to the implementation of insulation and A/V barriers in standard or high-performance building envelopes. If the industry had established ANSI installation standards and licensing requirements, new installers would not be able to work until they had received adequate training in all areas of the foam installation process, safety, quality assurance, and the related design and environmental considerations. Without standards and installer licensing, consumers have no basis on which to evaluate which installers will perform the work in a competent manner. To add to the lack of industry-recognized credentials, typically the lowest bid wins the job regardless of the experience, qualifications, and capabilities of the installer.
Introduction to the problems and their causes
Unfortunately, the ongoing foam price wars have been accompanied by a sharp increase in problem installations. It’s no exaggeration when I hear industry experts say that they’ve seen more foam quality problems in the last two years than they had in the preceding two decades. The following information is background to my experience with what is happening in the industry.
So, what are the actual causes of foam problems?
The causes of foam problems typically fall into three major categories. These generally include application/design, processing, and installation issues. Foam problems can result from bad or damaged chemicals, processing equipment problems, improper substrate preparation, improper installation/technique, improper environmental conditions during the foam installation, improper environmental conditions during the foam cure period, or improper maintenance of the environmental conditions the foam is exposed to after the installation has fully cured. ASTM or other laboratory tests performed under standard conditions do not necessarily emulate conditions installers often experience on site. On a hot summer day with black tar paper on the outside, the roof deck can reach temperatures as high as 180°. This condition will require a different installation procedure than a 70° wall on the north side of the same house on the same day. Installers can’t rely solely on generalized information in Installation Manuals or in Product Data Sheets to know when to adjust their work to the changing conditions and locations in which they work. They have to understand what is behind the basic guidelines the manufacturer provides in order to adjust accordingly. For example, some specify a minimum and maximum pass thickness, and some specify a maximum daily coverage. Knowing why the pass thickness is limited, and when core temperature conditions will allow the next pass or a greater coverage depth, can prevent foam problems caused by a substrate that is too hot or has an inappropriate pass thickness. Understanding what the core temperature threshold is, and being able to measure it, are critical in determining if a pass thicknesses is too great, or when core conditions allow for improved productivity.
Application/design Defects or Omissions
While there has been a dramatic increase in the use of foam and a disproportionate increase in the frequency of foam installation problems, not all building envelope problems are related to the foam material itself. Assembly and performance problems can be the result of design errors, material choice errors, or the result of changes in environment. Designers must know that they can only use this high-performance material in applications and assemblies that will not create other serious building envelope problems. This applies to all types of high-performance thermal envelope assemblies, no matter what type of insulation is used. Tight, well-insulated construction is desirable in terms of energy use, but high-performance building envelopes require designers and installers to pay attention to the building science implications of their work, usually in the form of moisture problems. Also, as new foam materials are introduced to the market that are intended to improve building performance, it is important to determine if new and old materials in an assembly are compatible. For example, SPF does not adhere well to materials that contain polyethylene, polypropylene, or some chemical additives. Originally, peel-and-stick membranes that were used for window and door opening transitions and flashings had to be “torch-applied” to make them compatible with SPF. The major manufactures have since modified the polyethylene outer layer of these membranes so that foam would bond to the material and create a durable and air tight air barrier transition. Some A/V coatings and membranes are temperature sensitive, and the heat of reaction of SPF can melt the bonding material, releasing the foam and the A/V material from the substrate. Many designers (and installers) do not understand how the physical properties of the materials relate to where and when those materials are best suited. Open-cell foam, for example, should not be used below grade and should not be installed in a roof before the roof is weather tight. Open-cell foam can take on water which dramatically affects its performance. While open-cell foam may be able to dry out over time, the amount of time it takes to dry out depends on the environment that the foam is in. If the foam is in a roof that leaks, water that is in the cavity between the plywood deck and a polyethylene vapor retarder may never dry out. Open-cell foam requires a vapor retarder in climate zones four or five and above. Most open-cell foam manufacturers publish the number of heating degree days above which their product requires a vapor retarder. Open and closed-cell foam both need vapor protection if they are in a location where there is a high vapor drive for an extended period of time (swimming pools, etc.). Generally, the drying potential of the assembly must exceed the wetting potential. For example, if you have an indoor pool or greenhouse with foam insulation in the enclosure, the warm, humid indoor conditions will usually be constant for the life of the structure; therefore, the enclosure assemblies can never dry to the inside, so there should be a vapor permeable exterior sheathing material on the outside to permit drying. This would be a non-standard type of construction, designed to prevent vapor migration from the inside and permit drying to the outside. Typically, this would require a ventilated wall or roof design with no vapor-impermeable materials on the outside. This is just one example of the designer/installer needing to understand which environmental and assembly conditions require special preparation or protection of the foam material and the structure to avoid a building envelope failure.
Hybrid insulation systems are another potential problem, but this is addressed well in the codes, and is a topic for another article.
Foam Chemical Defects
Even products that have been around for a number of years can have problems. Some manufacturers’ materials will vary slightly from lot-to-lot. Some manufacturers make changes in the chemicals without notifying installers. This can impact how the foam processes, and modifications that change the specific gravity of the A and B sides will affect readings in ratio monitoring equipment. Even so, factory control of processing conditions and the quality assurance protocols in mass production equipment are far better than the small-scale production equipment used in field installations. The likelihood of chemical problems is much lower than distribution and installer problems. In addition, most problem foam installations using any given product have been preceded by a large number of successful installations using the same product. Nevertheless, there are a number of documented foam problems that were traced back to foam chemical formulations. Manufacturers generally guard the information about these occurrences of quality control problems to reduce the impact on their sales. These manufacturing problems are usually quickly corrected, and generally include the appropriate support for the foam installer in remediating the problem installation.
Shipment and storage
Some chemical problems don’t develop until after the foam chemicals leave the factory. During shipping and storage the chemicals must be maintained under conditions that will not damage the material. While foam manufacturers typically recommend that the chemicals should be kept above freezing while in transit, and usually specify this on their shipping papers, we often had to request this protection, especially during swing periods of the year. Frozen material should be rejected when received. As a contractor, I refused a number of winter shipments from various manufacturers that arrived at our dock at temperatures well below freezing. In some cases, usually during swing periods of the year, the shipping papers did not indicate that the product should be kept above freezing while in transit, a protocol that was the shipper’s responsibility. We requested “protect from freezing” as a matter of course in our purchase orders, but this was not always an effective strategy. In other situations, the shipping papers had been marked “Protect from freezing,” but the trucking company had let the material sit in trailers rather than keeping it in heated warehouses between legs of the trip to the foam contractor. Also, foam installers should always maintain recommended minimum chemical temperatures in their rigs during cold-weather installations. Overheating can also be a problem. The B-side component of most closed-cell foam systems (2005 and newer) have blowing agents that can boil at temperatures that can easily be reached during shipment, storage, or at the job site. Many shipments arrived at my facility in trucks that had sat in the sun during hot weather for extended periods, resulting in over-pressurized drums with the ends bulged out to the point that the drums wouldn’t stand upright. Overheating can also occur in contractors’ trucks or trailers in transit or while at the job site. I have never seen a training program that addressed either temperature issue adequately; it is likely that many potentially damaged shipments are accepted and used by installers who don’t realize that they can degrade the resulting quality and/or yield of the foam.
Another cause of foam problems resulting from chemical defects can be the use of chemicals that are past their shelf life. After the use-by date, some products require mixing to avoid separation of the chemicals, and some chemicals contain additives that deteriorate or are lost over time.
Processing Issues Off-ratio foam:
Unlike most building materials—which come off the delivery truck needing only to be cut to size and fastened in place—spray foam is actually manufactured on site, in a mobile low-tech “factory.” This allows a continuous application, a critical characteristic of high-performance air barrier systems. Spray-applied foam’s ability to be “continuous” is one of the major advantages of siteprocessed foam compared to board stock. Ideally, the installer’s pumping equipment combines the A-side and B-side chemicals that comprise the foam in a near-perfect 1:1 ratio, but partially restricted or improperly maintained equipment can result in foam that is hard and brittle, or sticky and soft, depending on the chemical component imbalance. Off-ratio processing can also be caused by chemicals that are too cold or too hot. Some foam installers use equipment with ratio-monitoring equipment that will set off an alarm or turn off the pump when the mix ratio exceeds the manufacturer’s tolerance range, but this is more the exception than the rule. This equipment can also monitor pressure and temperature, other key quality control concerns. It also records compliance with processing parameters which can be a strong defense for an installer if a problem does occur. Installers who do not have automatic monitoring equipment should periodically verify their machine’s performance by manually checking its calibration, but this practice is seldom used. A lower-tech and less effective method of tracking the foam ratio is to weigh the A and B drums periodically, but some or all of the material already in place may be off ratio. Improperly conditioned supply chemicals are the most common cause of off-ratio processing. Going off ratio due to equipment wear and tear is usually a gradual process that results from any of a number of equipment setup or maintenance issues that can be seen as a trend if equipment is calibrated regularly. An experienced technician may or may not be able to see the foam going off ratio as it is happening, but new installers, for certain, will not be able to immediately tell if they are off ratio. The tendency for an installer who does see off-ratio foam occur, such as when a supply chemical runs out or is otherwise interrupted, is to spray over bad material once the equipment problem has been addressed; however, this can lead to problems later when the bad material is exposed to environmental stresses.
Test Shots are not performed properly
Making test shots prior to starting to install foam in a building is best practice. Product quality should always be verified before foam is permanently installed. Test shots should be performed after any adjustments to the equipment or supply material. Test shots are not always performed. Test shot quality should only be assessed by someone that is qualified to verify speed of reaction, cell size and shape, material color and uniformity, its lack of lead and lag symptoms, surface texture and feel (not sticky, friable, snappy, etc.) or free of an improper odor.
Installation Defects and/or Omissions
Installation problems fall into four general categories – problems with preparation, poor application and installation technique, or inadequate follow-up. These problems are all the result of a lack of training and a failure to follow best-practice procedures, including industry-standard quality assurance protocols. The foam installer must be able to run a business, understand the chemistry of the material, know all of the installation best practices, and have a consistent in-house quality assurance program. Many large commercial projects incorporate these into the project specifications, but installers serving the residential and small commercial markets have no real requirements that ensure a good outcome. While the general contractors should not have to be responsible for verifying foam processing temperatures, mix quality, or ratio, there are things they can do to assure a quality installation. General contractors typically know how to oversee their tradesmen, but this is new territory, so most are unlikely to have the experience to know when the foam installer is making a mistake. Methods the general contractor can use to assure a good project during the work is a topic for another discussion.
Temperature and moisture
Even if foam is properly mixed with good-quality chemicals, success still isn’t guaranteed. Improper application or failure to allow for changes in environmental conditions can lead to a variety of “after the gun” defects. Foam manufacturers provide limits for ambient and substrate moisture and temperature conditions. Installers should know these limits for each product they install, and be equipped to verify that they meet these requirements under any conditions and for any substrate.
Seasonal cold temperatures can limit when foam can be installed or how it is cured. Foam should not be installed in ambient conditions or on too-cold substrates. The rate at which foam is allowed to cool down during the cure period may also need to be controlled to avoid thermal shock and delamination. Temporary heat and temporary insulation can be used to extend the installation season.
Because water is a blowing agent for polyurethane foam, the substrate material the foam will be sprayed against must also be clean and dry. Foam blown against a damp surface will be “overblown” where it contacts the substrate, and adhere poorly and have a lower density in this layer. Foam with lower densities is more prone to shrinkage when “thermal shock” occurs, even months after the installation. Hygroscopic materials like OSB and plywood can feel dry to the touch while still holding a lot of moisture, so best practice is to always use a moisture meter to verify that the substrate moisture content is within the manufacturer’s specifications. Using open-flame heaters is a common cause of wet surfaces in cold climate projects. In addition to moisture impacting adhesion, foam will not adhere to (is not compatible with) some common substrate materials. This is typically only an adhesion issue, but it may have an impact on the chemical reaction of the foam’s raw materials. Bonding or adhesion problems generally require surface preparation or primers to assure product continuity with the substrate, a necessity for air barrier performance. Some substrate coatings and fully-adhered membranes are also prone to a loss of adhesion to the primary substrate when exposed to the heat of reaction of the foam during the cure period. These coatings and membranes may require mechanical attachment or retaining, at least until the foam has fully cured. When new substrate materials are encountered, an installer should always perform an adhesion test prior to starting the permanent installation. There is a list that outlines substrate compatibility properties available to the industry. Closed-cell foam gives off a lot of heat as it cures. That’s not a problem as long as the foam is applied in relatively thin layers—or “lifts”—that allow excess heat to dissipate between layers. If an inexperienced operator piles up too much foam at one time, the heat can’t escape because of the insulating properties of the foam. Once the temperature rises beyond a critical level, the resulting foam can shrink excessively after it cures. Overheated foam can also result in blowholes, hidden voids, internal scorching, and may even cause fire to break out (see “Massachusetts Fire Officials Urge Caution with Spray Foam,” JLC Report, Oct. 2011). Foam that is sprayed onto substrates that are too cool may not bond correctly, and the foam will have an unusually high density. A too-hot substrate can cause a different problem – foam that has a density that is too low and may therefore be prone to thermal shock. A thinner first pass may be required to “prime” the surface and assure that the subsequent passes will be isolated from a too-hot roof or south-facing wall. To minimize these kinds of problems, most high-end manufacturers of closed-cell foams offer summer and winter formulations of their products, and some even have spring/fall formulations for the swing seasons. This can help, but local conditions can easily trump the time of year. A south-facing roof deck covered with black roofing felt may be hot to touch even in cool weather, and the foam should be installed differently on this deck than on the north-side of the same house on the same day. Temperature swings during the work day can also have implications for the installer. A cold fall morning may indicate a winter formulation, while a hot afternoon the same day and a hot south-facing roof substrate may require switching to a summer formulation, or using pass thicknesses at the low end of the manufacturer’s recommended range with longer cooling periods between passes. Most installers do not understand this, or are unwilling to make these kinds of adjustments because of the impact on their productivity.