If YETI can make a cup that keeps water cold or hot for hours and a cooler that holds ice for hours, then why aren’t we building houses with that same material?

Question

If YETI can make a cup that keeps water cold or hot for hours and a cooler that holds ice for hours, then why aren’t we building houses with that same material?

In: 824

Answer 1

Yeti cups and other thermoses use a vacuum as insulation. Heat can transfer in three ways: radiation, convection, and conduction. You can’t *really* stop radiation, although you can slow it down. You also can’t really stop convection, but that isn’t relevant to keeping heat inside a thermos.

Conduction is the big one. Hot liquid touches the cup and makes it hot. The hot cup touches the air and makes *it* hot. Most insulation works by keeping the hot stuff from touching anything else. The insulation in your house does that: the fiberglass is full of pockets of air. Because air is less dense, it doesn’t transfer heat as well through conduction. So all the air trapped in the fiberglass slows down how fast heat transfers between the walls on either side.

Many thermoses work by using the best thermal insulation of all – *nothing*. The cup is made from two pieces. A vacuum pulls out most of the air between them. That means there’s nothing in there to conduct heat away. Some still does move through the walls of the cup itself, but it’s slower that way.

You can’t make buildings that way because it’s a lot harder to perfectly seal *all* of a building like that. Even if you did, a vacuum puts a lot of stress on the walls, trying to pull them in. You would have to reinforce the walls – again, not really a problem with a small cup made out of relatively thin metal that doesn’t have to hold anything up.

Various insulation solutions are a much better idea, especially because things like fiberglass help stop fires from spreading.

EDIT: I have been informed that vacuum panels for building insulation are a thing. Neat! I can imagine some of the limitations, like making it harder to change features on those walls, like adding power sockets and whatnot. Also, yes, double-pane windows are vacuum sealed, which is great for insulation but only a small part of the overall surface area of the wall (unless you’re talking commercial building that’s like 90% window).