| Fire Resistance of
Concrete Homes* Of all construction
materials, concrete is one of the most resistant to heat and
fire. That fire resistance gives houses built with
insulating concrete forms certain safety advantages. And those
advantages give builders and buyers yet another reason to
consider using ICFs for their next project.
How well do ICF walls hold up in a fire?
Unlike wood, concrete does not burn. Unlike steel, it does
not soften and bend. Concrete does not burn until it is exposed
to thousands of degrees Fahrenheit -- far more than is present
in the typical house fire.
This has been confirmed in so-called
"fire-wall" tests. In these tests, ICF walls were subjected to
continuous gas flames and temperatures of up to 2000°F for as
long as four 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 [like BuildBlock ICFs]. In contrast, wood frame
walls typically collapse in an hour or less.
Do they stop fire from spreading?
Concrete walls 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 of less.
Will the 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"
measure 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.
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