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Frequently Asked Questions


Question Topics

Settling and Foam Cracking  |  R-Value Loss of 50%  |  Hot Roofs & Roof Leaks  |  Trapping Moisture in Stud Cavities  |  Off Gasing & Fire

Q: When my house settles, will the foam crack and separate from the studs leaving an air void?
(Settling and Foam Cracking)
A: Any product that is misapplied will not perform as stated on the technical data sheets.  This includes open celled foams which have the tendency to separate from surfaces in cold climates and form large air-pockets if off-ratio or if the surface is wet.  With closed cell foams in all types of construction, both residential and commercial, elongation and tensile strength numbers are greater than that of sheet rock and actually helps reduce the impact (nail popping and drywall separation in truss uplift) in both cooling and heating environments.  In both the NAHB and CCMC studies, the substrate actually separated from the studs while the foam remained intact retaining an air-tightness seal.
Q: Another insulation contractor told me that closed cell foam will lose 50% of its R-value over time.  Is there any truth to this?
(R-value Loss of 50%)
A: R-value loss with closed cell technology is very similar to that of most insulation in that the K value actually increased and decreased with temperature.  as temperature drops, thermal resistance (R-value) actually increases to a point (roughly 20F) and then declines slightly.  The overall average thermal resistance remains constant at the numbers stated on the technical stat sheets.

Thermal drift where the blowing agent (ba) is replaced by air over time... initially this impact is greatest in the first year or so of operation.  This is related to the initial R-value and Aged R-value numbers that are reported on technical data sheets.  The reduction in R-value is minimal (8.2 to 7) or somewhere around 15%.  This is why we stated Aged values or make the distinction between aged and initial.  The thicker the application, the more R-value is retained.  So thickness and density have an impact on the loss or migration of ba.  Skins also have an impact on ba drift.  Thermal resistance numbers are taken on samples without skins or core samples.  If skins have an impact on thermal resistance and drift, which we believe does and studies support, then numbers reported on technical data sheets may, in fact, be understated from the start.

R-value degradation of 50% of more is indicative of air movement within and through traditional insulation materials.  All traditional insulation materials other than closed cell foams rely on trapping still, dry air within the fibers or cells of those traditional products for thermal resistance.  These traditional insulation materials are fiberglass, mineral wool, cellulose and large open celled foams.  If air moves through the insulation with filtration or within the insulation as with convection thermal resistant (R-value) can be degraded by 50%.  This effect can be compounded by air pockets or gaps and seams in the insulation.  A 3% void area in a stud cavity can reduce overall R-value in that cavity by 15%.  Both of these number are reported in the ASHRAE Handbook and are based on actual research conducted on various products.

Closed cell foams insulation differently.  Trapping and insulating gas within millions of microscopic closed cells of the polymer matrix, closed cell foam is not affected by air infiltration; as a matter of fact, closed foams have been tested to meet air barrier requirements based on ASTM (E283) testing protocol.  By nature of being a closed cell foam and by having a very efficient R-value per inch, convection within the the stud cavity is eliminated as well.  Closed cell foams are the best system to properly seal a cavity.  properly applied, it will seal against any air filtration, due to "creep" - unseen imperfections in the stud cavity are sealed as well.  No seams, No gaps, No errors, No conductive or infiltration related R-value loss.
Q: Should I be concerned with the temperature of my roof deck if closed cell foam is sprayed directly against the heating.  Also, what happens if I have a roof leak?
(Hot Roofs and Roof Leaks)
A: Multiple studies have proven that non-ventilated roofs (spray foam applied directly to the underside of roof decks) do not significantly impact roof or roofing materials durability.  These studies have shown that roof deck temperature is more determined by roof covering color and roof orientation.  There is some heightened roof deck temperature with this application and most research has found that by not ventilating, roof deck temperatures have on average been found 2-3% higher than with ventilated roof decks.
Q: If closed cell foam is considered to be a vapor retarder, wouldn't it trap moisture inside the exterior wall assembly and create wood rot? (Trapping moisture in stud cavities)
A: Closed cell spray foams are used widely as a roofing system.  A roofing system by design is meant to keep water out and the interior dry.  Closed cell foam applied to the underside of roof decks keep the roof deck from moving due to temperature changes which result when the roofing materials on that deck are put under stress.  Because the foam adheres to everything very tightly, the roof moves less and the potential for nail loosening and popping and roof deck separation and leakage is less.  Should a roofing system fail due to poor workmanship or in some other manner, the closed cell foam beneath that deck will localize the leak.  In other words, without the foam, the leak could be somewhere near the peak and migrate through more porous insulation materials to some other point where the natural path of least resistance will allow the water to move until it collects causing damage to roofing and roof deck materials or leak into the structure itself, creating more damage.  Foam under a failed roof will prevent the water from migrating from where the actual penetration is, "localizing" it, thus reducing water damage to roofing substrates and the interior while making repairs easier and less costly to perform.

Although closed cell spray foam is a roofing system and will prevent air movement and air infiltration, it is still a "breather."  Moisture can and does "flow through" closed cell foams but at a much reduced rate and in microscopic amounts in between the cell structure of the polymer matrix.  With over and and half million closed cells filled with an insulation gas per cubic of this stuff, you can see how only very small amounts of moisture in vapor form can actually move through foam.  But it does.  Building with wet materials is often the case, but unless the entire surface of a web building material is covered and closed-cell foam moisture applied in vapor form has the ability to out gas in another direction.  Studies conducted by the University of New York have shows that throughout the year, it is common that building materials wet and dry in terms of elevated relative humidity of the material.  The relative humidity is of little concern as log as the percentages are below saturation point and the vapor becomes liquid water.  Once at saturation within the wall, there are still opportunities to find a way out of the cavity as conditions change and water returns to a vapor state.  The advantage of closed cell foams is that when moisture is present, the flow from hot to cold and more to less (2nd law of thermodynamics) are:

  • Moisture is reduced
  • Temperature differentials are lessened to reduce the potential for condensation
  • Air flow is reduced to prevent more moisture and introduction of unconditioned
  • Air into cavity and convective thermal insulation (R-value) loss
Q: If my house were to catch on fire, would the spray foam give off dangerous fumes?
(Off Gassing and Fire)
Basically citing the Tech Checks and the research done at the University of San Francisco and the University of Denver Poison Control Centers.  Everything does burn, if it doesn't burn and off gas something, then it melts and off gasses.  The University of San Francisco Fire Research Center, in a study funded by NASA, chose 300 commonly found household building materials (including closed cell spray polyurethane), burned them and collected data on smoke developed, flame spread and lethality of smoke in order to find out of the survivability potential in house fires.  What was learned was that polyurethane was slightly less dangerous in terms of off gassing, spread of flame and smoke developed than that of Spruce, Pine, and Fir.  The foam was slightly less dangerous that the wall assembly it is sprayed on.

The second test wasn't really a test but a long-term study on the health effects of living with cured polyurethane foam.  The results reported in the Journal of American Medical Associate confirmed that no long-term health risks are associated with exposure to cured polyurethane.  The study went on a bit to editorialize somewhat saying that many reports and news stories about the health affects and fire characteristics of spray polyurethane foam were unrealistic and unfounded in study.