What are the Causes of Foam Problems

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 in the industry and the diagnostic, inspection, and remediation services I offer.

So, what are the actual causes of foam problems?
The causes of foam problems typically fall into three major categories. These generally include chemical, installation, and application/design issues. Foam problems can result from bad or damaged chemicals, equipment problems, spray technique errors, improper substrate preparation, improper installation, 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. A hot summer day with black tar paper on the outside, the roof deck can reach temperatures of 180°. This condition will requires 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 Installer Manuals or in Product Data Sheets to know when to adjust their work to the changing conditions and locations in which they work. You have to understand what is behind the basic guidelines the manufacturer provides in order to adjust accordingly. For example, 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 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. Assembly and performance problems can be the result of design errors, material choice errors, or the result of changes in environment. A cold fall morning may indicate a winter formulation, while a hot afternoon the same day and a hot roof substrate may require switching to a summer formulation or using a pass thicknesses at the low end of the manufacturers recommended range with longer cooling periods between passes.

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 change 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 found in field installations, so the likelihood of chemical problems is much lower than distribution and installer issues. 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 sales, and the manufacturing problems are usually quickly corrected and generally include support for the foam contractor in remediating related installations for the same reasons.

Some chemical problems don’t develop until after the foam chemicals leave the factory. During shipping and storage, the chemicals must be in maintained under conditions that will not damage the material. 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 this 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 transit to the foam contractor. I have never seen a training program that addressed this issue, so most foam contractors do not measure the temperature of the material when a shipment arrives; therefore, most would not refuse a delivery that was likely to contain damaged material. Overheating can also be a problem. Most closed-cell foam systems (2005 and newer) have blowing agents that can boil at temperatures that can easily be reached in storage or shipping scenarios. Many shipments arrived at my facility in trucks that had sat in the sun for extended periods, resulting in over-pressurized drums with the ends bulged out to the point that they wouldn’t stand up. Overheating can also occur in contractors’ trucks or trailers in transit or while at the job site. Another cause of foam caused by chemical defects is 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 over time.

Installation Defects and/or Omissions
Installation problems fall into four general categories – problems with preparation, material processing, 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 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 solid in-house quality assurance program. Many large commercial projects incorporate these into the project specifications, but installers serving the residential market have no real requirements that ensure a good outcome. While the General Contractors should not have to be responsible for 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.

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 provides the continuous material characteristic that is one of the major advantages of site-processed foam as compared to board stock. Ideally, the Contractor’s pumping equipment combines the A-side and B-side chemicals that make up the foam in a near-perfect 1:1 ratio, but partially clogged or incorrectly adjusted equipment can result in foam that is hard and brittle, or sticky and soft, depending on the chemical component imbalance.

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.

A lower-tech but less effective method of tracking the foam ratio is to weigh the A and B drums periodically, but the material already in place may be off ratio. Going off ratio is usually a gradual process that results from any of a number of equipment setup or maintenance issues. An experienced technician can usually see the foam going off ratio as it is happening, but new contractors usually have to see bad installed foam to learn this lesson. The tendency is to cover up bad material once the equipment problem has been addressed, but this can lead to problems later when the bad material is exposed to environmental stresses.

Shipment and storage
Other problems can be attributed to improper shipping and storage of foam chemicals after they leave the manufacturer’s factory. As a Contractor, I refused winter shipments from various manufacturers that arrived at our dock at temperatures well below freezing. While foam manufacturers typically recommend that the material 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 by Foam Contractors, and the Foam Contractors should maintain recommended minimum chemical temperatures in their rigs during cold-weather installations.

Overheating can also be a problem
Most closed-cell foam systems 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 have been in the sun during hot weather for extended periods, resulting in over-pressurized drums with the ends bulged out to the point that they wouldn’t stand upright. I have never seen a training program that addressed either issue, so many potentially damaged shipments are probably accepted and used by contractors who don’t realize that they can degrade the resulting quality and/or yield of the foam.
Temperature and moisture. Even if foam is properly mixed with good-quality chemicals, success still isn’t guaranteed. Improper application or failure to a allow for environmental conditions can lead to a variety of “beyond the nozzle” (after the gun?) defects.

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. But if an inexperienced or careless operator piles up too much foam at one time, the heat can’t escape. 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’s sprayed under conditions that are too cool, on the other hand, will not bond correctly to the substrate material. A too-hot substrate is another cause of foam that has a density low enough to be prone to thermal shock at a later date. A thinner than recommended first pass may be required to “prime” the surface and assure that the subsequent passes will be isolated from a 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 roof deck covered with black roofing felt may be hot to touch even in cool weather, and the foam should be installed differently than the north-side wall of the same house on the same day. Temperature swings during the work day can also have implications for the installer.

Too-cold conditions
Seasonal cold temperatures can also 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.

Substrate issues
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. (figure 5 shrank months after the install) Hygroscopic materials like OSB and plywood can feel dry the touch while still holding a lot of moisture, so if there’s any doubt, it’s a good idea to use a moisture meter to be sure 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, foam is not compatible with some common substrate materials. This is typically an adhesion issue, but may involve an impact on the chemical reaction of the 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 membranes are also prone to a loss of adhesion to the primary substrate when exposed to the heat of reaction from foam during the cure period. These coatings and membranes may require mechanical attachment or retaining, at least until the foam has fully cured.

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. In addition to the foam contractor processing and installing the foam properly, foam contractors and the designers must know that they can only use this high-performance material in applications and assemblies that will not create serious building envelope problems. High-performance building assemblies are more sensitive to interior and exterior environmental conditions and water infiltration because the assemblies generally are more air tight and have a lower drying potential. 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 put more pressure on designers and installers to pay attention to the building science implications of their work. In addition to moisture and water problems, as more new materials are introduced to improve building performance, it often takes a major failure resulting from a new combination of new and old materials in an assembly to find out that they are not compatible. For example, SPF does not adhere well to materials that contain polyethylene, polypropylene, or some chemical additives. Originally peel-and-stick membranes we now use for window and door openings and through-wall flashings had to be torched to make them compatible with SPF. The major manufactures modified the polyethylene outer layer of the membranes so that foam would bond to the material and create a durable 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 Contractors) 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 and this 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 conditions of foam is in. If the foam is in a leaky roof cavity between plywood and a polyethylene vapor retarder that was installed the day after the foam was installed, it may never dry out. Open-cell foam requires a vapor retarder in climates zones four or five and above. Most open-cell foam manufacturers publish the number of heating degree days some of which they feel 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. 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 out unless there is a vapor permeable exterior sheathing material on the outside. This would allow the wall assembly to dry out during the seasonal cycle, but this would be a non-standard type of construction, designed to address the need for drying. Typically, this would require a ventilated wall or roof design with no vapor-impermeable materials on the outside toward the vent spaces. This is just one example of the Contractor 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.

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 contractors 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 provide. You can’t just buy a pump and be effective in this industry, at least, not for long. Foam Contractors are providing a service at the construction site that is normally performed 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 at their disposal.

But the slowdown in the construction industry has encouraged many existing insulation contractors (glass fiber, cellulose, etc.) and other contractors in previously unrelated trades (masonry, paint, damp-proofing, carpentry, etc.) to diversify into installing field-applied foam and air/vapor (A/V) barrier coatings. While new Foam Contractors historically have been experienced first or second tier installers 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 Contractors 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 Contractor licensing, consumers have no basis on which to evaluate which Contractors will perform the work in a competent manner. To add to the lack of industry-recognized credentials, in this economy, the lowest bid wins the job regardless of the experience, qualifications, and capabilities of the installer.