Of all construction
materials, concrete is one of the most resistant to heat and
fire. Such fire resistance gives houses built with insulating
concrete forms (ICFs) certain safety advantages. Those advantages
give builders and buyers yet another reason to consider using
ICFs for their next project.
do ICF walls hold up in a fire?
Experience shows that
concrete structures are more likely to remain standing through
fire than are structures of other materials. Unlike wood, concrete
does not burn. Unlike steel, it does not soften and bend. Concrete
does not break down until it is exposed to thousands of degrees
Fahrenheitfar more than is present in the typical house
These Fire ratings have
been confirmed in so-called fire-wall tests. In
these tests ICF walls were subjected to continuous gas flames
and temperatures of up to 2000F for as long as 4 hours.
None of the ICF walls ever failed structurally. All of the ICFs
tested were of the flat or uninterrupted grid
type, having no significant breaks in the concrete layer . In
contrast, wood frame walls typically collapse in an hour or
Do they stop
fire from spreading?
have also proven more resistant to allowing fire to pass from
one side of the wall to the other. This is especially of interest
in areas with brush fires that could spread indoors.
The fire wall test confirms this rule for ICFs
once again. Part of the test measured how well the wall slows
the passage of heat and fire from the side with the flame
to the other side. The ICF walls tested did not allow flames
to pass directly through. They also did not allow enough heat
through to start a fire on the cool side for 2-4 hours. In
contrast, wood frame walls typically allow both flame and
fire-starting heat through in an hour or less.
foam add fuel to the fire?
The foams in ICFs
are manufactured with flame-retardant additives. These prevent
the foams from burning by themselves. If you hold a match to
the material, it will melt away.
Of course, in a house fire, the foam may
be subjected to constant flame from other materials burning
nearby (wooden floors, fabrics, etc.). The Steiner Tunnel
Test measures how much a material carries fire from
an outside source. In the test, technicians line a tunnel
with the material, run a fire at one end, then measure how
far the flame spreads. The flames travel about one-fifth as
far down a tunnel lined with ICF foams as they spread down
a tunnel lined with wood.
Can the foam
give off harmful emissions?
Practically any organic
material, be it wood or plastic, gives off emissions when it
is subjected to intense heat or flame. The Southwest Research
Institute reviewed the numerous existing studies of fire emissions
and concluded that the emissions from polystyrene foams are
no more toxic than those of wood.
should I take to make my house fire resistant?
No matter what
your walls are made of, there is no sense playing with fire.
Building codes require covering the inside face of exterior
walls with a fire-resistant material, such as gypsum wallboard
or a stout plaster.
In areas prone to outdoor fires, it is wise
to finish the exterior with a fire-resistant material, too.
Favorites are Portland cement stucco and masonry.
And of course the more you can design your home
to limit the exposure of flammable materials like wood and
fabrics, the better.
Evidence suggests that
ICF walls may be safer in many ways than wood frame in a fire.
Using ICF walls in your next home would provide an important
and effective measure of fire safety.
Chammas, and Lemay, Insulating Concrete Forms for Residential
Design and Construction. New York: McGraw-Hill Inc., 1997.
VanderWerf and Munsell, Insulating Concrete
Forms Construction Manual. New York: McGraw-Hill Inc., 1996.