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Foam As A Fire Barrier
by David B. SouthUrethane foam is an excellent fire barrier when used on the exterior of a building. There are numerous examples of urethane foam roofs saving a building from fire. Burning brands, that can include anything from hot embers to large pieces of burning wood, can lay on a urethane roof for a considerable time before burning through. The urethane insulated roof will simply char. If there is no external heat source, the fire will go out. Urethane requires a lot of heat to keep burning. Where the heat can radiate to the atmosphere, the urethane makes a superior fire barrier.
Back in the days before we worried about heat sinks, thermal barriers and the like, we insulated a common wall in a mattress factory in Twin Falls, Idaho. We sprayed one inch of urethane foam on the metal wall to protect the office from losing heat into the furniture storage area. One night, the mattress storage area caught fire. That fire burned for a very long time.
The Fire Marshall told me that the fire was against the building's common wall for better than an hour before they could cool it. He was amazed that the heat did not come through that common wall.
It didn't because the urethane insulation sprayed on the wall reflected the fire's heat back into the storage area, rather than allowing the heat to come through. The Fire Marshall declared that he knew of no other material, besides concrete, that could hold back fire for the time they needed to extinguish that fire.
read more ... Foam As A Fire Barrier" uses an interesting construction technique: an air form is placed, and layers of various materials are sprayed on from the inside.