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Wetmesh

A house covering that holds water for evaporation in a passing fire front.
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Since having a hose spray a large halo of safe environment of water is both expensive in volume and energy, I propose a wet house cover idea.

The cover mesh, made of a fire proof material with a weaved shape and structure that is hydrophilic, can be placed on the roof ridges and rolled out to cover the home as a fire guard. The roof ridge sections have hosework that connects to water supplies and dribbles water down the mesh. The whole system will take time to charge as the water has to flood the full mesh surface but once loaded, less water will be needed as only evaporated sections need replacement.

I am imagining Wetmesh to be quite light, not unlike mosquito netting, but this may not prove to be the case if a workable charge of water is to be held. The water supply will need a head great enough to reach home ridge lines. This is not a instantaneous solution so forewarning will be needed to install and load.

Again Wetmesh has limits , falling trees, a fire so severe it outstrips pipework supply but if evacuation is decided, a hope is still a hope.

wjt, Jan 12 2020

Whole house fire blanket https://www.frontie...ech.2019.00060/full
like this but with water? [Chairborne Hero, Jan 12 2020]

[link]






       Yes [Chairborne Hero], having a two layer fire-blanket would allow water to wick through the cover. Although, the experiments look more like the use of an integrated build material rather than an emergency throw.
wjt, Jan 12 2020
  

       I'm all for bringing back turf as a roofing material.
Layered as follows, top to bottom:
1. grass
2. waterlogged mattresses
3. drip irrigation to keep the mattresses damp
4. normal roof
  

       To further optimize it, the roof could be terraced, like a garden. A mechanism resembling "movable stacks" in libraries would allow one terrace at a time to move sideways, revealing a walkway for access for gardening.   

       An even more ambitious project would be a living house consisting of a closely spaced array of lodgepole pines coaxed over decades to grow horizontally to form a roof, then left for additional decades to form a solid mass of tree, with windows and doors preinstalled before the closely packed trees grow together, and interior bark polished smooth and cleaned to interior standards. If windows and doors are made of refractory material, and the logs are thick enough, then the fire will not be able to burn through the trees before burning out.   

       This problem of fireproofing might also be solved by simply increasing the dimensions of existing log cabin designs, i.e. scaling up the wall log diameter from 8 inches to 36 inches, scaling up the door thickness from 2 inches to 9 inches, and using two-inch-thick slate roof tiles. A fire would take a long time to burn through that.   

       An approach that's actually baked would be an underground bunker, commonly available as a prefab shipping container unit for this specific purpose.   

       To halfbake it, I propose a "coffee and cream" fireproofing, consisting of flooding a moat around the house with water (the coffee) and then deploying aircraft-hangar fireproofing foam dispensers to blanket the entire house in a thick layer of foam (the cream).
sninctown, Jan 12 2020
  

       There's always the "Not living in the middle of a flammable arboreal environment" option, although that doesn't seem obvious to many humans ...   

       What is the described system intended to protect against ?   

       Ignition can come from several sources:   

       1. Falling or wind-blown burning fragments.
2. Ground-level fire spread through flammable material in proximity to the dwelling.
3. Radiative heating of structure leading to flashover.

The design will probably give some protection against the first problem, ensuring any sparks land on a relatively cool, wet surface. The second effect can be prevented by a simple firebreak, ensuring there is nothing to provide a path for fire. The third mechanism is challenging; the water distribution must be such that despite evaporation caused by thermal radiation, all the vulnerable surfaces are maintained below a temperature at which a spark or ember can't trigger ignition.
  

       To achieve that, single distribution lines - along the roof ridges - may be inadequate, as the effectiveness will attenuate proportional to the distance from the line.   

       The exact number and location of distribution lines, and the volumes of water required, are best determined by practical experiment. This will of course mean burning a number of houses to the ground. We are fully prepared to assist with this process (the "setting fire to stuff" part, anyway).
8th of 7, Jan 12 2020
  

       True, a physical envelope is always going to outweigh a theoretical one. I did envisage the mesh dropping from the roof line to the ground and a larger or complex home would need designed charge lines. This idea might even get personal.
wjt, Jan 12 2020
  

       How do you stop the water freezing? Won't the mesh make it harder to clear snow off the roof?
pocmloc, Jan 12 2020
  

       The pipework would no doubt be kept dry until required, like a dry riser fire main in a tall building.   

       The system is unlikely to be needed in an operational mode in conditions of snow, which would tend to reduce the possibility of fire.   

       If the mesh were permanently fixed, it might indeed cause snow to build up more readily. The inevitable loading on the roof structure could be compensated by fillng the entire interior of the building with concrete, which would have the additional benefit of increasing its fire resistance.
8th of 7, Jan 12 2020
  

       //fillng [sic] the entire interior of the building with concrete//   

       If you instead filled the entire exterior with concrete, you could still live in the house and the fire couldn't get to you.
MaxwellBuchanan, Jan 12 2020
  

       Mmmm, how much concrete do you think that would require?
pocmloc, Jan 12 2020
  

       Depends - the bigger the house, the smaller the exterior.
MaxwellBuchanan, Jan 12 2020
  

       OK for a standard 57-room house with the usual outbuildings, how much?
pocmloc, Jan 12 2020
  

       Rather a lot; in fact, you would need to fill the entire Universe that wasn't the house with concrete, and unless you mix in a fair proportion of Dark matter to bulk it up, you're going to struggle.
8th of 7, Jan 12 2020
  

       Yes, exactly. But as I pointed out, the requirements are reduced for a larger house.
MaxwellBuchanan, Jan 12 2020
  

       I'm now wondering if that is true. How much concrete would I save, both as a percentage, and as an amount, if I used (1) a modest 10-bedroom assistant Gamekeeper's cottage annexe, or (b) the main house?   

       Is the actual volume of exterior not the same in both cases?
pocmloc, Jan 13 2020
  

       No.   

       Why don't you come up and show the rest of the class why that is ?   

       <Proffers whiteboard marker to [poc]/>
8th of 7, Jan 13 2020
  

       <draws furiously on blackboard>this doesn't seem to work very well!
pocmloc, Jan 13 2020
  

       Yes, of course. You're more familiar with green wax crayon, aren't you ?   

       <Consults notes/>   

       Well, a whiteboard marker hardly counts as a sharp object, thankfully.
8th of 7, Jan 13 2020
  
      
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