For fires such as brush fires, forest fires, etc., in which you have advanced warning of an approaching fire, this flame-retardant tent (similar to a termite tent) could be placed over the home to protect a house. You could sell these to homeowners, and insurance companies would love this, and be likely to help make them affordable to the average homeowner by giving discounts on premiums or rebates. This seems like a much more effective approach than spraying a garden hose on the roof (which evaporates before the fire even gets there), and homeowners wouldn't have as much of a sense of helplessness when a fire is coming.
A real entrepenuer could drive up to a neighborhood that's threatened by fire and sell 'em out of the back of a truck, although the fire dept. might be a little suspicious of you if you start profiteering off of fires...-- onecentJay, Oct 27 2003 Barricade Gel http://www.barricadegel.com/squirt and save [oneoffdave, Oct 04 2004] Asbestos house http://news.bbc.co....england/1680844.stmWhy bother with the tent when you can make the whole house from asbestos... [alligator_al, Oct 04 2004] Marshmallow Coat http://www.halfbake.../Marshmallow_20CoatHave your home and eat it too. [Colonel Panic, Oct 04 2004] I'm not entirely sure why roof tiles aren't made of fire retardant materials. Or perhaps they are?
Last forest fire season, we discussed the fire retardent properties of diaper gel. In an emergency, you could always cover your house in Pampers.-- DrCurry, Oct 27 2003 They are. That's the main reason roof tiles and stucco are so popular in Southern California and other fire-prone areas, but often the eaves are still wood, and wood studs are still the norm. Rather than rebuild a house or drastically alter the design, one could buy this tent as a preventative measure, to have on-hand in case of emergency.
But diapers ain't a bad second option...-- onecentJay, Oct 27 2003 Nice first idea. Welcome to the bakery, Jay.-- krelnik, Oct 27 2003 You can now get spray on diaper filling to fire proof your property [link].-- oneoffdave, Oct 28 2003 Um, yeah, that was what we were talking about.-- DrCurry, Oct 28 2003 Must be topical again as the TV here had two programmes about it over the weekend. Strange as bush fires aren't that common in the UK in the autumn.-- oneoffdave, Oct 28 2003 Mostly crop fires from farmers burning off stubble, if I recall correctly.-- DrCurry, Oct 28 2003 Adapt the idea from the marshmallow coat. When you return to your home you can make the world's biggest smore!-- Colonel Panic, Oct 28 2003 Unfortunately, unless you tent had some magical properties your house would simply combust due to ambient heat inside the tent anyway. Even if you created an oxygen free vacuum inside, the materials would still suffer thermal breakdown and turn into a charred carbon mess.-- Reverend_Cobol, Oct 28 2003 Ah, good point.
What if the tent perimeter was a circle well away from the house, and the tent was an open-topped cylinder or cone? That way heat could vent upward, but fire would not reach the house. A telescoping pole attached to the roof of your house would hold the tent up from the center via guy wires.-- krelnik, Oct 28 2003 [Reverend_Cobol] Walls are fairly good at insulating. Yes, it would get quite hot, but I doubt it would be dangerously so.-- Detly, Oct 28 2003 We're talking about a tent of some sort here to protect from free range fire, say a grass fire or forest fire, not a bonfire in the backyard gone out of control. A fire of any magnitude, doesn't move by flames migrating across available fuel sources alone, but also spreads by the ambient heat moving ahead of the fire causeing fuel to spontaneously combust. These fires are insanely hot, enough to melt road signs in some cases. A simple study (http://spe.univ-corse.fr/MFF/IJWF-Paul1.pdf) models the spread of a fire over a 2.3 cm deep bed of pine needles. The area around flame front of this test fire was 600-700 deg. C. Spontaneous combustion temp. for wood is around 500 deg. C (though it will char at lesser temps). Fire shelters used by fire fighters resemble the device onecentJay proposes, however, their thermal breakdown point is also around 500 deg. C, at which point their effectiveness is drastically reduced. They also rely on ground cooling to help funnel off convective heat, i.e. they only work because they are close to the ground. A similar device covering a house would not benefit from ground cooling, and thus could not offer a similar effective level of protection for very long at all.
That being said, if such a tent was constructed that reflected radient heat, was able to divert convected heat, and did not suffer from thermal breakdown at 600 + deg. C temperatures* for up to 90 minutes, you may have a workable idea. Increasing the radius of deployment away from the house would help. If you could construct a highly convective laminar air flow around the outside of the tent to direct heat up and away from the tent itself, that would also help. If you could create a vacuum between the layers of the tent, that would also cut down on the convective heat transfer of the tent, however at this point we're basically building a wall around our house, not a portable tent. We've also drastically increased the cost and deployment time.
* I was unable to find accurate data reflecting actual thermal conditions (max. temp., temp falloff at various ranges from flame front, etc...) to do any rigorous calulations, so I made these remarks based off of the study I referenced.
[Detly] I agree about the insulating properties of walls, and in fact have both studied and modelled heat convection through various types and thickness of walls. For the purpose of my arguments though I am assuming a portable tent-like structure, not a permanent wall around your house (which, incedently, better have a ceiling as well to offer full protection)-- Reverend_Cobol, Oct 29 2003 In that context, it's fascinating to see the pictures of burnt-out homes in California, with the backyard shrubs and trees still standing tall and green. Makes you wonder if Nature has a sense of humor.-- DrCurry, Oct 29 2003 Thank you for the information. :)-- Detly, Oct 29 2003 random, halfbakery