Cellulose insulation vs. foam insulation


R-value, safety, and cost

Foam plastic is required by International Building Code and the International Residential Code to be separated from the interior of a building by an approved thermal barrier to protect against fire. Cellulose insulation is not required to be separated from interior space because it will not ignite readily when exposed to fire. Actually, cellulose insulation is officially classified by building codes as fire blocking material, which slows the spread of fire through closed cavities in building assemblies. Tests also qualify cellulose insulation as an effective fire stop around steel through penetrations in fire-rated walls.

More specifically, foam insulation installed in attics and walls must be covered by a fire ignition or thermal barrier such as: gypsum wallboard, corrosion resistant steel, wood structural panel, mineral fiber insulation, intumescent paint or cellulose insulation. However, once a house is engulfed in flame, ignition and thermal barriers are of little benefit because the foam insulation will be directly exposed to fire or will be ignited through auto ignition (i.e. temperature of ≥ 700 ºF).

The reason there are such rigid codes concerning foam insulation is that once ignited, fire spreads rapidly, creating very high temperatures and dense toxic smoke in a matter of seconds. In a NFPA 286 corner test conducted at a prominent fire testing laboratory, a supposedly Class 1 (i.e. can be installed in a residence) foam insulation material reached flashover conditions in 44 seconds. This test is supposed to run for 15 minutes before reaching flashover. (Fire tests comparing cellulose insulation to both fiberglass and foam insulations indicating the far superior performance of cellulose insulation can be viewed at www.tasconindustries.com. 

The fire hazards associated with foam insulation are real, and everyone, from the architect, building code official, building inspector, building contractor, and most of all, the home owner, should be concerned that building codes directed at foam insulation are strictly enforced.

While foam insulation has become popular because of its unique ability to expand and its appearance of being ‘high-tech,’ there are other facts that should be considered. The three most important factors of residential insulations are: R-value, safety and cost. As already noted, from objective evidence and testing, it is clear that foam insulation’s safety is problematical due to its fast burning and toxic smoke producing characteristics in home fires.

To surround your house with foam insulation, a product that is highly flammable and produces large quantities of bellowing toxic smoke when ignited, there would need to be good reason for doing this. One might think that the reason would be the energy savings gained by having a better R-value. Actually, foam insulation doesn’t have an appreciable higher R-value than cellulose insulation. Both of these insulation products carry a 3.6 to 3.7 R-value per inch. To make matters worse, foam insulation is rarely installed to completely fill the wall cavities because in so doing it requires much more (1) labor expense to shave flush with the framing the excess foam insulation to allow the gypsum wall board to be properly attached and (2) extra foam insulation material that then must be disposed of. What this means to you, the homeowner, is that you actually get less than the full R-value quoted by the contractor.

Could the reason be that installing foam insulation is less expensive than installing cellulose insulation? Actually, the facts are quite different. Installing foam insulation costs 2-3 times more than installing cellulose insulation!

So why choose foam insulation over cellulose insulation? You wouldn’t if you knew the real facts!

A quick comparison

R-Value 3.5–3.7 per inch 3.6–3.8 per inch Applied Foam generally does not completely fill wall cavities thereby shorting claimed R-value.
Air Tightness — Air changes per hour (ACH) 0.20 0.30 Building experts recommend that ACH not be less than 0.35 in order to maintain a healthy environment.
Greenness Little The greenest of the green 85% of cellulose insulation is recycled paper. Foam is made from petroleum distillates. Foam has no recycled content. Foam requires much more embedded energy to manufacture than cellulose
Smoke Developed ≤ 450 ≤ 25 Due to excessive smoke developed index foam must be covered with thermal/fire resistant barrier when installed in inhabited areas
Hazardous Yes No Some components of foam insulation are toxic, although the finished product is not.
Fire Resistance Yes, but ... Yes See “Smoke Developed” above.
Fire Block & Ignition Barrier No Yes Cellulose approved as both. Can reduce cost considerably.
Flame Spread ≤ 25 ≤ 25 Widely-used Class 1 foam insulation failed the 15 minute NFPA 286 Test in 44 seconds. See also“Smoke Developed” above.
Cost (R-30 Attic) $2.75/sq. ft. $0.60/sq. ft. Foam costs are 2 to 3 times higher than the cost of installing cellulose without providing any offsetting benefit.
Cost (2X4 Wall) $1.20/sq. ft. $0.55/sq. ft. Foam costs are 2 to 3 times higher than the cost of installing cellulose without providing any offsetting benefit.
Sound Reverberation Control NRC = 0.70 NRC = 0.80 Cellulose reduces sound reverberation (echoing) more than foam.
Sound Transmission Control STC = 39 STC = 49+ Cellulose has greater sound blocking capability than foam on similar wall assemblies.
Thermal Barrier Required Yes No Foam must be separated from the interior of a building by an approved thermal/fire barrier.

The Honorable James R. Langevin (D-RI)

Statement before the U. S. House of Representatives — Foam Fire Safety Act

February 17, 2005

Mr. Speaker,

Soon I will be joined by my colleague from Rhode Island in reintroducing the “Foam Fire Safety Act” to reduce the injuries, deaths, and property damage that result from fires fueled by products containing polyurethane foam.  This sensible legislation directs the Consumer Product Safety Commission (CPSC) to implement a rule within one year that ensures that mattresses, bedding, furniture, and other products containing polyurethane foam meet a new open flame standard. The new level of protection will decrease the destructiveness of fires in homes and buildings around the country and prevent unnecessary tragedies.

Polyurethane foam is found in mattresses, upholstered furniture, carpet padding, soundproofing insulation, and many other products found where we live and work. Polyurethane foam is also one of the most flammable consumer products, and firefighters refer to it as “solid gasoline.” Between 1980 and 1998, mattress, bedding, and upholstered furniture fires killed almost 30,000 people in the United States. During the same period, these fires injured more than 95,000 people.

The Consumer Product Safety Commission (CPSC) first began looking into creating stricter flame retardancy standards for foam in 1993. Twelve years later, the process continues without result, and all Americans are left without common sense standards similar to those already in place in California and Great Britain.

My legislation, which is endorsed by the National Association of State Fire Marshals, requires polyurethane products to meet a new “open flame” test, which is equivalent to having a candle right next to the foam. Currently, mattresses and furniture must only be able to withstand the equivalent of a lit cigarette. While the CPSC has begun a rulemaking process for an open-flame test for mattresses, we cannot afford to delay any longer.

Polyurethane foam serves as kindling for fires, and a stricter standard would prevent deaths and property damage. In my district, polyurethane soundproofing foam contributed to the deaths of 100 people at the Station nightclub fire in West Warwick, Rhode Island, on February 20, 2003. Because of the abundance of foam, the building was engulfed in flames within 3 minutes, and firefighters who were located just down the street could not arrive in time.

As the two year anniversary of the Station fire approaches this weekend, Rhode Islanders are reminded of this horrific event. Unfortunately, we are frequently reminded of our own inaction to prevent future disasters as similar fires continue to occur around the world. On New Year’s Eve, ceiling foam ignited in a nightclub in Buenos Aires, Argentina, killing nearly 200 attendees. We must act now before another tragedy strikes.

I urge my colleagues to join me and the other co-sponsors of this bill to reduce the risk of polyurethane foam fires. Passage of this responsible measure will make American homes and workplaces safer.

Three Massachusetts home fires linked to spray-foam installation

The Massachusetts Division of Fire Safety warns fire chiefs about the dangers of negligent installations of spray polyurethane foam

Posted on Jul 7 2011 by Martin Holladay, GBA Advisor

[Photo credit: Dave Curran]

Green Building Advisor Fire investigators suspect that a fire that destroyed a $5 million home in Woods Hole, Massachusetts was ignited when excess heat was generated by the exothermic reaction that occurs during the installation of spray polyurethane foam.

UPDATED 8/16/2011

The Massachusetts Division of Fire Safety (DFS) is investigating the causes of three house fires that were ignited while insulation contractors were installing spray polyurethane foam.

According to Tim Rodrique, the director of the DFS, investigators suspect that the fires were caused by the exothermic reaction that results from the mixing of the two chemicals used to make spray foam.

One of the fires destroyed a $5 million home on the exclusive Penzance Point peninsula in Woods Hole on February 10, 2011. The house was being renovated at the time. According to the Cape Cod Times, “firefighters were somewhat stymied due to spray-on foam insulation. … Similar insulation has proven deadly in the past. In 2008, Robert Cowhey of Springfield was spraying soy-based foam insulation in the attic of a North Falmouth home. The chemicals were located in a truck outside the home in two 50-gallon tanks, but somehow they ignited and Cowhey died in the ensuing fire.”

Robert Cowhey, the victim who died in the North Falmouth fire, worked for Green Mountain Insulation of White River Junction, Vermont. Cowhey was installing SoyTherm50 spray foam insulation when the fire broke out.

According to the Cape Cod Times, “The first sign of trouble came when a co-worker smelled a burning odor and noticed smoke billowing in the fireplace on the floor beneath the attic. He and another worker tried to reach Cowhey and put out the fire with an extinguisher. The two were stymied by the intense heat and smoke, however.”

According to an OSHA report on the North Falmouth fire, “The company was spraying expanding foam insulation in the attic of a single-family, two-story house that was undergoing renovations. The spray foam properties were such that it could generate sufficient heat immediately following its application to cause spontaneous combustion. Among the chemicals being used were diisocyanate; flouroethane and lead naphthenate. There was no fire extinguisher in the attic space during the spraying process and no rescue plan in the event of a medical emergency. The employer had not developed or implemented a fire protection or prevention plan. Access to the attic was via a 3’ wide by 6’ long hole in the second floor ceiling. The attic was not ventilated. A flash fire occurred in the attic in which an employee died.”

OSHA further notes that “the products used were SoyTherm 50 and SoyTherm 100 and are diphenylmethane diisocyanate (MDI) based. A technical bulletin issued in November of 1993 by the Polyurethane Division of the Society of the Plastics Industry, Incorporated located in New York City warns of the spontaneous combustibility of the material. SoyTherm is known in the industry as an open cell foam insulation.”

A warning is issued to all Massachusetts fire departments

On July 1, 2011, Stephen D. Coan, the Massachusetts State Fire Marshal, issued a memorandum 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. …

“Information gathered by the Division of Fire Safety from different manufacturers indicate that there are several possible scenarios that could lead to a heat build-up, and a possible fire scenario. These are: improper application techniques (excessive thickness, or spraying new material into the already applied rising foam) and/or improper mixtures of the chemicals at the application nozzle.

“Based upon this information, the Division of Fire Safety is recommending that you work with your building officials to determine if such applications are taking place within your community and, if so, to also make contractors in your communities aware of this potential fire hazard and encourage that they follow application instructions accurately.”

A similar case in Quebec

In a case similar to the Massachusetts fires, a net-zero-energy house in Hudson, Quebec burned to the ground on May 25, 2010. The Quebec fire erupted a short time after workers finished insulating the home with spray-foam insulation. In all of these cases, investigators assume that installers applied the spray foam too thickly, thereby trapping the heat generated by the chemical reaction that creates the foam.


OSHA hazard information bulletins

May 10, 1989

Office of Field Programs
Director of Technical Support
SUBJECT: Safety Hazard Information Bulletin on Fire Hazard of Polyurethane and Other Organic Foam Insulation Aboard Ships and in Construction

The Seattle Regional Office has brought to our attention a Potential fire hazard involving the use of Polyurethane and other organic foam insulation found aboard ships and in building construction. Instances of fires associated with this insulation, have been documented demonstrating the need for better understanding of the fire hazard of this type of material.

Rigid polyurethane and polyisocyanurate foams will, when ignited, burn rapidly and produce intense heat, dense smoke and gases which are irritating, flammable and/or toxic. As with other organic materials the most significant gas is usually carbon monoxide. Thermal decomposition products from polyurethane foam, consist mainly of carbon monoxide, benzene, toluene, oxides of nitrogen, hydrogen cyanide, acetaldehyde, acetone, propene, carbon dioxide, alkenes and water vapor.

All organic cellular plastics, whether or not they contain fire retardants, should be considered combustible and handled accordingly. Terms like “fire-retardant”, “flame-resistant”, and “self-extinguishing”, sometimes used to describe the combustibility characteristics of foams are valid measures of the performance of these materials under small fire exposure, and are not intended to reflect hazards under exposure to large scale fire conditions.

In building construction, fire usually is of serious concern because there may be storage of exposed foam, incomplete installation, other dangers of improper application and disposal practices, poor housekeeping conditions, and the potential for exposure to open flame from allied trades during certain construction activities.

Polyurethane and other organic foam materials are finding increased use on vessels because of their excellent insulating properties and light weight. Since serious fires involving the use of these materials have occurred on several ships, the United States Coast Guard has issued a Navigation and Vessel Inspection Circular No. 8-80, addressing the fire hazards of polyurethane and other organic foam materials.

Enclosed for your information are two bulletins which address the fire hazards of polyurethane and other organic foams

  1. United States Coast Guard Navigation and Vessel Inspection Circular No. 8-80.
  2. “Fire Safety Guidelines for Use of Rigid Polyurethane or Polyisocyanurate Foam Insulation in Building Construction,” Published by the Urethane Division, the Society of the Plastics Industry. One of, the major safety precautions to be taken around organic foams is to prohibit sources of ignition such as open flames, cutting and welding torches, high intensity heat sources and smoking. The safety recommendations of the foam supplier must be observed in addition to the minimum requirements set by OSHA for fire protection.

Please distribute this bulletin to all area offices, State Plan States and Consultation Project Officers.



Heat transmission modes

It is important to know how heat is transferred in fish holds. Heat is transferred by conduction, convection or radiation, or by a combination of all three. Heat always moves from warmer to colder areas; it seeks a balance. If the interior of an insulated fish hold is colder than the outside air, the fish hold draws heat from the outside. The greater the temperature difference, the faster the heat flows to the colder area.

Conduction. By this mode, heat energy is passed through a solid, liquid or gas from molecule to molecule in a material. In order for the heat to be conducted, there should be physical contact between particles and some temperature difference. Therefore, thermal conductivity is the measure of the speed of heat flow passed from particle to particle. The rate of heat flow through a specific material will be influenced by the difference of temperature and by its thermal conductivity.

Convection. By this mode, heat is transferred when a heated air/gas or liquid moves from one place to another, carrying its heat with it. The rate of heat flow will depend on the temperature of the moving gas or liquid and on its rate of flow.

Radiation. Heat energy is transmitted in the form of light, as infrared radiation or another form of electromagnetic waves. This energy emanates from a hot body and can travel freely only through completely transparent media. The atmosphere, glass and translucent materials pass a significant amount of radiant heat, which can be absorbed when it falls on a surface (e.g. the ship’s deck surface on a sunny day absorbs radiant heat and becomes hot). It is a well known fact that light-coloured or shiny surfaces reflect more radiant heat than black or dark surfaces, therefore the former will be heated more slowly.

Fire and Explosion Hazard Data

Flash Point (test method): Not applicable. The ignition temperature of rigid polyurethane foam is in the range of 700–800 ºF. The temperature must exceed 300 ºF for a period of time before the occurrence of degradation, which may lead eventually to self-ignition. At this temperature most solid combustible material will exhibit signs of charring, one of the first steps in ignition.

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