Energy efficiency is a high priority in today’s buildings as compared to the past. Chief reasons driving the change are the perceived benefits to the environment and most importantly, the economic benefit to the building owner and occupants.
Various methods and materials are used in modern building construction to achieve a higher performing building, in the sense energy efficiency. One such method is the use of Spray Foam as insulation.
This article is intended to only be a basic overview of Spray Foam Insulation with the majority of it concentrating on Spray Polyurethane Foam (SPF) since I have had several firefighters inquire about it recently.
What is Spray Foam Insulation?
Spray Foam Insulation can be categorized into two different types: Open Cell and Closed Cell.
Open Cell Foam Insulation:
Open Cell is a type of foam where the tiny cells are not completely closed and is less expensive because it uses fewer chemicals. It is a very good air barrier, but does not provide any type of water vapor barrier. It is much more sponge-like in appearance. It is often used for interior walls because it provides sound reduction by damping the movement of existing insulation. It is not recommended for outdoor applications.
Closed Cell Foam Insulation:
Closed Cell Foam Insulation is a much more dense type of foam than Open Cell. It has a smaller, more compact cell structure and is a very good air barrier as well as a water vapor barrier. It is often used in roofing projects and other outdoor applications, but can be used anywhere in the home.
In order to create the final SPF Insulation or sealant product, a chemical reaction of the two component parts, commonly referred to as Side A and Side B, has to occur. SPF products contain approximately 50 % Side A and 50 % Side B. This chemical reaction generates heat.
Side A contains very reactive chemicals known as isocyanates. Side B contains a polyol, which reacts with isocyanates to make polyurethane, and a mixture of other chemicals, including catalysts (which help the reaction to occur), flame retardants, blowing agents, surfactants and in some cases is made of natural sustainable products such as soybean oil, castor oil, and sucrose-based oils from sugar beets.
Spray Foam Insulation saves on energy costs and lowers utility bills. Studies by the US Department of Energy show that 40% of a home’s energy is lost as the result of air infiltration through walls, windows, and doorways. 
Insulation that is sprayed in buildings protects against moisture, and provides the benefit of reducing the chance of harmful mold and mildew. Eliminating mold growth reduces the likelihood of rotting wood in a home, and allergic reactions to mold spores.
As we stated earlier most of the recent fire service inquiries were about SPF so the rest of this article will focus only on SPF insulation.
Spray Polyurethane Foam, commonly referred to as SPF is a spray-applied insulating foam plastic which is installed as a liquid and then expands many times its original size. Spray Polyurethane Foam can be adjusted and have many different physical properties depending on the use desired. There are many applications for the use of SPF in the modern building envelope. The two most common uses of SPF in modern building construction are to insulate attics and wall cavities.
Designing Space SPF Overview Video:
Wall Cavity Foam Insulation Video:
UL 2011 Eave Experiment Comparison Video:
Another benefit of Closed Cell SPF is that it adds structural strength to the walls and roof, thereby making it more resistant to racking events, such as hurricanes and high winds. I see this benefit as a blessing and a curse! The blessing is that it makes the building stronger and rigid. However, the curse is that it could possibly make a roof assembly appear solid because it was so rigid. When in fact, the attic structural members were destroyed by the fire and firefighters stepping on to this roof could plunge into an attic full of fire. Later on in the attic section we will address what I observed at recent test at Underwriters Laboratory (UL).
Closed-Cell Spray Foam in Hurricane Sandy Aftermath – FOAM WEEK: Special Report YouTube Video:
Another very common use of SPF Insulation is in unventilated roofs. Unvented roof assemblies are becoming increasingly common construction alternative to traditional vented roofs. They are designed without ventilation openings, and the attic is conditioned like the rest of the living space.
Unvented roofs operate by the principle that venting is not necessary to control moisture accumulation. The following condition must be met in order for an unvented roofing assembly to function properly. The building envelope must be tight, including having adequate vapor and air barriers installed, which is generally accomplished through the use of Spray-Foam Insulation. SPF is sprayed directly on the underside of the roof deck to form an air, vapor, and thermal barrier. The foam sticks tenaciously to the roof deck and expands to fill cracks and voids that in a cold climate might allow warm, humid air to reach the back of the roof deck and condense. In a hot climate, the foam blocks humid air from entering the house, where it could condense on cooler surfaces. Unvented roofs have been allowed in the International Residential Code (IRC) since 2006.
One criticism of unvented roofs insulated with Spray Foam is that roof leaks are difficult to detect and could cause extensive roof sheathing rot before the homeowner notices any problems. The problem with this is that firefighters would be operating on a roof, that the sheathing is rotten, having no idea, because most likely the roof would sound solid when sounding it because of how rigid the SPF is when applied to the underside of roof.
Insulating and Air Sealing an Attic with Spray Foam (Short Version) YouTube Video:
As I mentioned earlier several firefighters have inquire about SPF lately. All of the inquiries have been about if a saw could cut through it. I will first off say I haven’t personally cut through a roof that was sprayed with SPF, but I am a technical panel member on the current UL attic fire study and watched Steve Kerber and staff cut through it in the overhaul stage of the testing. Steve Kerber was able to cut into the SPF with a K-12 saw without it gumming up the saw. However, as you can see in the picture, the roof stayed together even with a hole cut into it due to the SPF adhering to the roof. The SPF in this test was 10-12 inches thick as it would be in a residential attic.
SPF and Fire:
Spray Foam is a combustible material; the same can be said for most organic materials. Some foams are formulated with fire-retardants, exposed spray foam that comes in contact with flames can still result in a fire. The burn is usually brief unless there is enough heat energy to sustain combustion. When it exposed to flames it forms a layer of surface char, as well as producing combustible gases and smoke. Although the char will offer some degree of protection for unburned
Spray Foam to prevent it from further contributing to a fire, there are circumstances in which combustible gases build up typically, interior settings. In such situations, temperatures can rise high enough for the fire to flashover.
Since Spray Foam is combustible codes require barriers to protect from potential sources of ignition. This protection is accomplished two ways thermal barriers and ignition barriers.
A thermal barrier is a material, applied between foam plastics (including spray polyurethane foam) and interior spaces designed to delay the temperature rise of the foam during a fire situation and to delay or prevent the foam’s involvement in a fire. The International Building Code (IBC) and the International Residential Code(IRC) define an approved thermal barrier as one which is equal in fire resistance to 12.7 mm (1/2 inch) gypsum wallboard. In essence, the model building codes define inch gypsum wallboard as a prescriptive thermal barrier; approved equivalents (non- prescriptive thermal barriers) must perform as well as, or better than inch gypsum wallboard in fire testing.
Model building codes allow an exception to the thermal barrier requirement in attics and crawlspaces where entry is made only for repairs or maintenance (IRC) or for the service of utilities (IBC).
In these cases: The Spray Foam insulation is protected against ignition using one of the following ignition barrier
1 1/2 inch thick (38 mm) mineral fiber insulation
1/2 inch thick (6.4 mm) wood structural panels
3/8 inch (9.5 mm) particleboard (1/4 inch thick under the IBC)
1/2 inch (6.4 mm) hardboard
3/8 inch (9.5 mm) gypsum board; or corrosion resistant steel having a base metal thickness of 0.016 inch (0.406 mm).
The materials referenced above from the IRC and IBC are termed “prescriptive ignition barriers.”
Ignition barriers do not afford as high a degree of protection from fire as thermal barriers, but are considered acceptable for attic and crawlspaces where entry is limited
NFPA Fire Test YouTube Video:
Another fire service concern with SPF is in the application stage. A reaction of A- and B-side chemicals, when sprayed to form foam, releases heat (i.e., it is an exothermic reaction). Hopefully the contractors will remove all potential ignition sources and unnecessary combustibles due to the heat released or it could result in structure fire. Recently there has been several cases of this in Massachusetts and has lead the Massachusetts State Fire Marshal Stephan Coan to issue a memorandum(2) to the heads of every fire department in the state. The memo notes, Recently, the Department of Fire Services, Division of Fire Safety, has become aware of a number of fires involving commercially available spray-on foam insulation. At least 3 fires, one being a fatal fire, are believed to have been started during the application of spray foam insulation, and currently remain under investigation.
We have already mentioned before that Closed Cell SPF is an insulation that not only insulates very well, but it is also a vapor and air barrier. We have also covered that unvented attics are allowed in modern construction. So take a minute and digest that! We could now possibly have an attic that is sealed airtight with combustible material. This could create a very interesting situation in the terms of attic fires. This is currently being examined by the ongoing UL attic fire committee.
Watch for upcoming test results from UL in the future.
Excerpts about Attic Fires from FDIC 2013 Steve Kerber Video:
Attics are not the only place in a residential structure that Closed Cell SPF could affect the fire behavior in a structure. As stated before, one of the primary reasons this product is used is to be an air barrier along with insulate. The same principles that work all year around to keeping the convectional currents from passing through the structures envelope and stopping the external radiation heat from coming into the structure, will also influence the development of fire in a structure by keeping all the heat inside the structure.
SPF in Modern Building Construction:
Energy efficient is the name of the game in modern construction. The use of SPF Insulation can achieve this in many ways; therefore, it is widely used and is projected to grow at 13% per year from about $800 million in 2013 to $1.1 billion in 2015.(3) SPF Insulation is just one of many factors that change the buildings we respond too. Since we have covered what I feel are the Basics on Spray Foam, now in closing I just want to leave you with some thoughts of mine concerning potential issues we may have with increased usage of SPF.
Structure fires in application stage of SPF. Use caution and wear full SCBA while even investigating, these calls due to the toxic materials used and produced in these flash fires.
Use caution on roof operations. As mentioned before Closed Cell SPF makes the structural members that are covered with SPF very rigid. This is a benefit unless other none- SPF covered structural members are destroyed by fire. Take a look at this video of overhaul of a test burn. This roof was held intact and had to have a forklift to lift it up to drop it to the ground even though all the members below it were destroyed by fire. A firefighter stepping onto this roof could be enough of impact load to send the firefighter into the structure.
Use caution when called to medical incidents and you see SPF installer vehicles outside. While we cannot review all the potential health effects that could result from spray foam chemicals here and this specific information would be contained in the product MSDS you should understand that a worker could be exposed to SPF chemicals by breathing chemical mists or vapors, skin or eye contact, or ingestion. (4)
Use caution when opening up attics from below! Possible increases of backdraft or smoke explosion in attics since many attics are unvented now due to covering the underside of roof decking with SPF Insulation. Smoke that is trapped in these attics will become under ventilated and fuel rich only needing air.
While some of you may have already known about SPF Insulation, the intent of this article is to bring awareness of a commonly used product in modern building construction. Modern building construction presents many hazards for the fire service. In order for you to be up to date in this ever changing world of ours, you must be a student of fire behavior and building construction in order to survive.
You can learn more about this topic and many others by attending FDIC 2014 and attending my workshop (Modern Buildings the Recipe for Firefighters Deaths or Injuries!) on April 7th 2014.
Thanks for reading
Lt. John Shafer
Additional Reading: http://www.ecologices.com/pdf/scienceofsprayfoam.pdf