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Comment by lopmotr | Hacker News Reader

It's funny to think "obviously polyethylene is flammable, how did nobody notice" then realize my own house has expanded polystyrene and polyester fiber batts insulation under the floor. I wondered about fire risk but saw some vague claims by the manufacturers and that the local authority approved them, and just trusted that, despite these local authorities having a history of approving bad products. Decades ago, my dad was very critical of all polymer building insulation because of the fire danger. I thought he was just out of touch and obviously it wouldn't be allowed if it wasn't safe. This isn't the olden days! We're more strictly regulated now!

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Your home is presumably only 2-4 stories. So in the event of a bad fire you just evacuate. Probably the fire can be extinguished, but maybe it can't, either way you aren't inside, your insurer is on the hook for any increase in costs from products that did not perform. Maybe "the invisible hand" will fix that, maybe it won't, but nobody dies.

In a high rise residential building it's a nightmare to evacuate, so until that becomes necessary (as it did at Grenfell and one of the other phases looked at whether emergency services were wrong to delay so long and why that happened) the preference is to compartmentalize as you would on a ship (can't evacuate those either). As a result of this approach to fire fighting it's critical that fire cannot spread between compartments. Flat #1 is on fire, a team comes out, they fight the fire, maybe Flat #1 is completely ruined, but the people in Flat #2 are just annoyed by the smell of smoke and the debris, they aren't actually in danger. At Grenfell this cladding meant the fire was able to spread outside the building defeating compartmentalization, in hindsight once that happened it would be impossible to contain it.

So the height of the building isn't just why this is news, it's also why it was a problem.

According to Civil Defense documents, construction post-1945 was considered to be more vulnerable to the thermal and shock effects of nuclear weapons than pre-1945 construction.

Plastic materials were a villain. A black polyurethane couch could catch the rays of a H-Bomb fireball 100 kilometers array and within 15 seconds create a fireball in the room. Details like that create a lot of uncertainty about causalities.

Closer to home your Fire Marshall could demonstrate for you why you should not smoke in bed or what happens to a car when you light the passenger seat with a Zippo.

Common natural materials have safety properties against fire. For instance, if I got too close to a fire, a wool sweater would form a char, "ablating" like the Apollo spacecraft heat shield. An acrylic sweater would melt and probably transfer more heat to my skin and make it more likely that I get burned, if it doesn't ignite itself.

There's a reason polystyrene is used as the waveguide between the two stages in a thermonuclear bomb :\

I don't know of anywhere that allows "polyester fiber batts" as a component of insulation. You probably have fiberglass batts, which melt eventually but don't burn.

If the EPS (expanded polystyrene) is covered by fiberglass insulation and/or drywall, it will last sufficiently long for you to escape from a fire.

It's not glass wool. It's essentially the same stuff duvets are made from. Very comfortable actually! But maybe has some special fire retarding additive or something - I don't know.

Just looking up the product now, the brochure says "Please consult a fire engineer when specifying GreenStuf insulation ". That certainly didn't happen. Oops. But as another replyer said, it doesn't really matter for a normal house. It might burn down but you'd have escaped because of smoke alarms and just walking out the door.

The polystyrene is exposed to the outside with no covering.

You probably don't live in the same country as me so the rules are different.

... it really is polyester fiber. They say it's 100% polyester. Hope your wires are in conduit. And the EPS is just on the side of your house with no cladding? It'll get beat up just from wind-blown debris. Your construction ideas are very odd.

> If the EPS (expanded polystyrene) is covered by fiberglass insulation and/or drywall, it will last sufficiently long for you to escape from a fire.

No. EPS offgasses badly when heated. It also assumes that your coverage is 100% in drywall.

If you have fibreglass, then you are sunk. Rockwool/mineralwool then you are much better.

In the case of skyscrapers it breaks the basic safety concept.

Fires won't propagate up or down a properly built skyscraper except by the flames lapping up from floor 14 starting a fire on a floor 15.

I got my place insulated when i moved in, so every room is now a Celotex box. I remember wondering how they made it fireproof, but never looking into it.

Mind you, it's a garret in a mansard roof, so before the Celotex it was just wood and bitumen, not exactly fireproof either.

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