Science Forums 2

[CraigD]

Originally Posted by goku

what if we filled our atics with CO2 instead of fiberglass?

I’m guessing goku’s speculating that, because CO2 and other greenhouse gasses are believed to increase the average temperature of the Earth’s, filling a house attic with greenhouse gasses would increase the temperature of the air in the house.

The flaw with this idea is that the greenhouse effect results from material – greenhouse gasses in the case of an atmosphere, glass or other transparent sheet material in a greenhouse, etc. – allowing visible sunlight to pass through it, but absorbing and reemitting or reflecting the infrared light emitted by the sunlit surfaces below. Since the roof of the usual house is opaque to light well above and below the visible range, the greenhouse effect doesn’t play much of a role with it, regardless of what kind of gasses fill its attic.

The purpose of attic insulation is preventing heat escaping the house by heating the roof. Fiberglass blanket insulation is good at this, because it contains many small cells that limits the ability of the gas it contains to transport heat via convection. Though heavier gasses could be used to make slightly more effective insulation, unless encased in a gas-tight envelope (which would make the blanket troublesome to cut), they’d escape the fiberglass mat and be replaced with ordinary air, so it’s easier and cheaper to just increase the thickness of the blanket.

If you did have a transparent roofed house, the transparent material itself would likely be a more effective infrared reflector than any greenhouse gas-rich gas with which you could fill a gas-tight attic, so there’d be no point in using a gas other than ordinary air. Keeping such a house warm at night could be tricky – using multiple sheets of transparent material with gas baffles between them might work. Keeping the house from getting too hot during the day would be a challenge.