Stop the frost
January 25, 2007 9:54 AM   Subscribe

Frost Experts: how can i stop frost buildup on a window/door?

on most mornings, the "screen door" style door (with it's winter glass panes in) gets a heavy layer of frost on it. to the point of being opaque. anybody know how to prevent this? the screen door is the outer door with an exterior door opening into the room. the gap between the two doors is a couple inches.

on an related-only-in-concept note, the INSIDE of the windshield of my car has been doing this too.

i'd like all my windows to remain completely transparent, please help.
posted by qbxk to Science & Nature (8 answers total) 2 users marked this as a favorite
Rain-X should help. At the very least, it's cut my inside-car fogging/frosting down to almost nil.
posted by koeselitz at 10:02 AM on January 25, 2007 [1 favorite]

Check the seal, dehumidify, good luck. You may not be able to do much about it though.
posted by Nodecam at 10:15 AM on January 25, 2007

Also, like Nodecam said, you might not be able to do much. If you have this problem often, you probably live in a humid climate (when I lived in Boston, I couldn't stop this from happening no matter what I tried). You should invest in a squeegee; that should help remove the moisture, anyhow.
posted by koeselitz at 10:25 AM on January 25, 2007

Keep the inside of your car dry. Excessive moisture (snow, which ends up melting if it is sunny or if you run the heater, obviously) inside the cabin will condense on the windows and freeze when the temp drops below the dew point. Last time I had that problem I just set the heater to blow on the floor and cranked it up for my entire trip (~1 hour). Rain-X anti-fog works well, but it needs to be applied when temps are above 50, and it can be tricky to get just right.
posted by ganzhimself at 10:26 AM on January 25, 2007

The frost on the door is most likely from warm humid air from inside. To stop this, you'll want better weatherstripping on the regular door, not on the glass door.

For the car windshield, crank the defrost using outside air not recirculating air. It makes a huge difference. This fact was unknown to this Floridain when he became a Minnesotan.
posted by advicepig at 11:13 AM on January 25, 2007

If you always have your car air set to recirculate, change it to use outside air. A friend had constant frost on the inside of her windows. Making that one change cleared it up. With the air set to recirculate, moisture just builds up inside the car (and freezes on the windows when they get cold). Your heater should work just as well with outside air.

For your house door, the same principle applies (humid air + cold glass = frost), but it might be harder to figure out how to lower the humidity between the two doors without breaking the seal in either direction - unless as advicepig says the problem is that humid air from inside the house is leaking around or through the main door.
posted by whatnotever at 3:00 PM on January 25, 2007

Is the frost on your car windshield happening while you drive or while it's parked? The recirculating idea works if you're driving, but if it's happening while it's parked, then crack a couple of windows open just a tiny bit (1/8" gap is fine) and the humid air will escape before it condenses on the windshield, which cools off when you park the car.

You could crack open your storm door to get the same benefit, though that would also negate most of the benefit of having the glass pane in the door in the first place. The real solution there is fixing the weatherstripping on the main door.
posted by cardboard at 3:23 PM on January 25, 2007

Can't suggest anything for the outside of your door beyond surface treatments, but if the inside of your car windscreen is still fogging/frosting up after trying the suggestions above, get a big bag of silica gel kitty litter (the stuff that looks like little plastic beads), dump the contents into an old pillowcase, and leave that on the dashboard overnight. When it stops working so well, bake the gel in a low oven for a few hours to restore its magic moisture-sucking goodness.
posted by flabdablet at 4:12 PM on January 25, 2007

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