This article... http://static.monolithic.com/foam/fire_hazard/index.html ...describes what can happen to structures lined with unprotected urethane foam.
Basically, if they catch fire, they explode. It's true that urethane foam does not burn well in open air. But in an enclosed space, the foam is such good insulation that the heat reflects back and feeds the fire - even if the foam is a "less flammable" formulation. A single point of heat such as a welding torch is enough to start a fire that will fully engulf a warehouse in under five minutes. I know some hexayurts have been built with panels that are reflective- coated on only one side - which is put on the outside - leaving bare foam on the inside. If one of these caught fire, whoever was inside would probably die. My intuition does not tell me what would happen to a hexayurt built of foam panels with foil on both sides. Clearly, it would be harder to ignite the foam. But if something else caught fire inside the building, how quickly would the reflected heat intensify the fire? Would the thin aluminum evaporate, exposing the foam? Some panels have a plastic coating on the aluminum - would that evaporate and burn? Until I updated it, the page on hexayurt fire safety at Appropedia suggested that, since foam does not burn well (in open air), people might decide that a bare-foam hexayurt was safe enough. According to the article I linked, foam manufacturers used to think this way - telling people that if they lined their warehouse with foam, they could "cancel their fire insurance." After some unfortunate experiences with totally destroyed buildings, unprotected urethane foam is now referred to by fire experts as "solid gasoline." The drastic and counterintuitive difference between open-air foam and foam-lined enclosures - even huge enclosures like warehouses - suggests that any hexayurt materials should be fire-tested in the hexayurt configuration with realistic ignition sources (say, a sleeping bag or cardboard furniture) before being recommended for widespread use. One story in the article told about welders repeatedly setting the foam on fire and slapping out the flames with no problem - until one time when the tipping point of heat was reached, the building caught fire, and they barely escaped with their lives - running the length of the building with fire already overhead. Chris --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "hexayurt" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/hexayurt?hl=en -~----------~----~----~----~------~----~------~--~---
