This article provided in conjunction with CIMA (Cellulose Insulation Manafacturers
Foam is the future! At least that's what you would have to conclude from all the buzz foam
insulation products are getting these days. At the 2007 ICAA convention 13 of the exhibitors were from the spray
foam segment of the insulation industry. This is at least three times more than from any other part of the
industry. Foam has certainly gotten the attention of our fiber glass friends. The NAIMA booth at ICAA was filled
with "myths of foam" literature.
This leads to the inevitable question: "Just how good is foam?" Is this apparent
trend a fad, or is it really the future of residential insulation? As some CIMA members know, my roots are in
the foam industry so it's been suggested that I might be in a good position to comment.
The first thing to understand about foam is that there are basically two product categories:
half-pound open cell foam, and two-pound closed cell foam. Both are sprayed onto or into building assemblies as
liquid that foams and expands as it hits the substrate. Open cell foam typically has an R-factor of 3.5
to 3.7; the R-factor of closed cell foam is usually 6.0 to 7.0.
As insulation, foam works, and it works very well. It is all but impermeable to air movement, and
it is not subject to most of the factors that degrade the thermal performance of some fiber insulation
materials, e.g. convective heat loss, air infiltration, and transparency to radiant energy. As a material that
starts as a spray-applied liquid, foam fills cavities very well and is very effective at creating a tight
Sounds like a virtually perfect insulation, right? Not quite.
Like every other building material made by God or man foam has its strengths and weaknesses. The strengths of foam
are mentioned above. Here, as Paul Harvey would say, is the rest of the story.
Foam isn't perfect. Like cellulose, fiber glass, and every other insulation, foam
can be improperly installed. Temperatures, component proportioning, and installer technique are all critical
factors to a proper foam job.
A few years ago a friend from the fiber glass industry (Yes, I have some, and I'll bet you
do too.) called to report on the EEBA convention, which I didn't attend. He said that Greenfiber's
cellulose wall spray demonstration went well, and the demonstration of a fiber glass product was
okay, but the Icynene demonstration was "a disaster." Disasters sometimes occur on actual building
Foam is just as subject to installation problems as any
other material, but assuming proper installation of every material isn't foam the right choice for
thermal performance? Actually, no. It certainly isn't the right choice on a cost-to-benefit
The big hurdle foam has to overcome is its premium price. R-for-R open cell foam
costs at least two or two and a half times more than cellulose (or fiber glass for that matter). On the same basis
closed cell foam usually costs at least four times more than the fiber insulation materials.
What payback can a home owner expect for paying the price of foam? Compared to
fiber glass little; compared to cellulose, none. Here's why.
Take first the case of open cell foam. Using Icynene's R-factor of 3.6 the
installed R-value in a 3.5-inch wall cavity is 12.6. Cellulose at wall density would be 13.5 to 14. Fiber
glass could be as much as 15.
The foam salesperson will claim that the tightness of foamed walls and attics or
ceilings more than compensates for this lower R-value. (See how these ping-pong balls float in the tubes over fiber
glass and cellulose?!)
Maybe in the case of fiber glass that argument has some slight validity, but with
cellulose it falls apart. Put a blower door on a house insulated with well-installed cellulose, and you will
typically get a natural air change rate of 0.3 ACH or less. Test an identical house with open or closed cell foam
and you may get a reading of 0.2 ACH or less. Foam wins!
Not so fast. Indoor air quality experts are in virtual unanimous agreement that a
natural air change rate of at least 0.35 ACH is essential for a healthy living environment. Supplemental
ventilation is necessary for both the foam-insulated and cellulose-insulated houses. All the high price of the open
cell foam buys is a degree of tightness you can't use, and a lower installed R-value! Doesn't sound like a smart
choice to me.
Now let's look at closed cell foam. Totally fill a 3.5-inch wall with closed cell
foam and the installed R-value will be 21 to 24.5. The cost, however, would be astronomical. It would be far more
economical to go to 2 x 6 framing and use less expensive insulation.
Well, you don't have to spray the cavity full. Why not just spray two
inches for an installed R-value of 12 to 14. There's an idea.
But not a good one. The cost of doing this would be higher than filling the whole
cavity with open cell foam, and the same indoor air quality issues apply. The home owner would be paying a
super-premium price to make the home too tight for healthy living.
Now let me say that I don't believe in deliberately building leaky houses. You
make the house as tight as you can--within reason--then provide for controlled ventilation. That "within reason" is
an important qualifier. You certainly don't pay a premium price for no return on the additional investment. If
you’re building somewhere near the north or south poles closed cell foam makes some sense. I can't think of any
case where open cell makes economic sense.
The fact that it provides no cost-effective thermal performance benefits is the
biggest wart on the face of foam, but there are other drawbacks that may be important to some buyers.
· Most foams are all petrochemicals with embodied
energy much higher than even fiber glass. The embodied energy of foam is at least 60 times that of
· The so-called bio-based foams are produced from
materials that can used for many other purposes, including feeding the hungry. (Okay, that's pandering, but I
couldn't resist.) In any case, these foams are mostly petrochemicals. When a life-cycle analysis is applied
their embodied energy may be as high as or higher than the all-petrochemical products.
· The blowing agents of closed cell foams are
considered to be environmentally destructive. (But to be fair they have gotten much better in this regard.)
· There is often a great deal of non-recyclable
waste associated with foam installation.
· On the same theme. if carrying groceries home in
plastic bags and drinking from foam plastic cups is so bad—some communities have banned these items under
pressure from environmental activists—why do so many people who claim to be environmentalists think it’s a good
idea to spray thousands of cubic feet of the same material into homes?
· At least one of the components of some foams is a
(But the foam itself is not toxic in any sense.)
· Some foams are highly flammable and none offer
the fire resistance benefits of cellulose.
· Foams have little and usually no recovered
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