How a foil-wrapped home survived the Caldor Fire as everything around it burned | Hacker News Reader

How a foil-wrapped home survived the Caldor Fire as everything around it burned

sfchronicle.com

37 pointstoss120 comments

There were 3 cabins in the area that didn't burn down, the one wrapped in foil, a house built from concrete (a friend of mine, you can see his in the background of the second image on that site), and another that wasn't particularly special. Interesting that all 3 survived, perhaps the topology, fire direction, or other factor made that pocket more survivable.

My buddies house (concrete construction) should be the default in fire prone areas, the fact that we keep building wooden structures in fire zones doesn't seem logical.

Concrete does poorly in earthquakes compared to wood. I dont know which disaster is a bigger threat, but with wildfires you generally have enough time to evacuate.

I think properly reinforced concrete is an acceptable building structure for earthquake zones.

My real point is that buildings should be designed for the area they are in. So zones that have earthquake, flood, hurricane, fire, etc. risk should be designed against the risk they face. You do see that to some extent, but it's glaringly lacking a lot of places.

> But wrapping the family cabin in protective foil isn’t something that can be easily accomplished as the fire nears. Even if a homeowner has rolls of the wrap on hand, the biggest obstacle is time. Covering a typical cabin in foil takes four to five people six to seven hours and thousands of staples.

I question this estimate. I recently covered about 1/3 of my 1700 ft^2 house in plastic to prepare for painting, using staples. That took two of us under three hours, and each piece had to be cut to size, and the placement was crucial. Neither of us are particularly fast or skillful at it. With a big roll of foil that just needs to overlap, I bet we could do the whole house in just a few hours more.

The estimate is important, because if it can get done that fast, in my high fire risk area it makes sense to have the foil on hand just in case.

...why do you live in a high fire risk area? I'm sure it's lovely and all, but I'm surprised you can even get insurance.

Why does anyone live in California? Or the gulf states? Or the Midwest "flyover" states?

People live where they live. Not everyone can uproot themselves and their family to move someplace else with other, different issues

Or in the case of the small cabins pictured, you'd think you could have a one-piece cover made of similar materials, like a giant car cover, packed away and just pull it over the structure before fleeing.

This is common with window protection (wood) in hurricane states

I never knew this was a thing, but it makes perfect sense, and apparently works pretty well too.

"The foil, usually applied with thousands of staples, isn’t off-the-shelf Reynolds Wrap, though it is sold in rolls. It’s aluminum on the outside, woven threads of polyester and fiberglass inside, and laminated with a high-temperature adhesive, according to Dan Hirning, founder of Firezat, a San Diego company that sells the foil."

Regular aluminum foil would probably just tear when you try to staple it to a building. Having some kind of backing material to give it some strength sounds sensible.

The backing material is also insulation. The R-value is low but the objective is to reduce the heat transfer so it doesn't reach the ignition point, not to actually keep it cool.

Can we make giant rolls of this and enclose large swathes of land to make giant fire cells (while a fire is ongoing)? Or more simply, could this be used to wrap currently burning areas of land to prevent spread?

Technically, yes, we can do this. There are practicality issues to deal with. If you use trees to mark your fire perimeter, what do you do if a tree burns down? They can catch fire from on top just as easily as from on bottom. probably more so as every time I've ever seen the aftermath of a forest fire it's always been left as stumps.

Then, there's structural rigidity, deployment times, and the sheer mass of material people would have to deploy to make a firewall like this work. You would need something like an 18 wheeler stuffed to the brim with this foil and support beams to stave off a football field worth of space.

The forest service will occasionally do this for remote structures that are at risk. It works surprisingly well!

When you consider physics of a forest fire, there are lots of unintuitive-sounding solutions that come up. One of them is to seal up the underside of your deck to prevent embers from getting lodged inside.

So, I’m on our neighborhood FireWise committee here in Austin. The training we have received indicates that the primary direction that embers would be coming to your deck would be from the top side, not the bottom. So, sealing the bottom doesn’t help you, but making sure the top side is properly sealed will help.

Of course, you do have to worry about things blowing under the deck, but there the solution is 1/16th inch metal screening at the perimeter of the deck to keep the embers from getting anywhere close to being under the structure, as opposed to sealing the underside of the deck.

You are correct that in most residential wildfire situations, the primary concern is embers. We saw that in Steiner Ranch. But there are many other factors, too — like all those wood fences that act like a wick to take the fire from one house to the next to the next and so on. Or your proximity to the WUI. Or many other things.

If you haven’t checked them out before, I highly recommend the FireWise resources at http://www.nfpa.org/Public-Education/Fire-causes-and-risks/W...

https://archive.is/AHLRM

I don't think I would want to return to a home in a hellish burn zone, with all of my neighbors gone.

It's an interesting tradeoff. With large flooding events you are often better off with a destroyed house and an insurance payout than with an intact house surrounded by rubble and destroyed infrastructure. On the other hand saving the house preserves a lot of things of sentimental value. Fires are probably similar, even if they are not quite as destructive to all infrastructure

Yeah. If I were going to build in a wildfire zone I would build a house engineered not to burn (yes, it's quite possible) but how much value is there if you come back to a house with the surround destroyed?

I’ll take not having my house burned down to the ground, over the alternative.

I might still have a host of issues to deal with, but that would be a fantastic one to not be on that side of that equation.

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