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pilotdog68 t1_j6jydk0 wrote

Reply to comment by amoore031184 in How do I prevent condensation on the windows from causing water to accumulate on the windowsill? by teddythepooh99

I'm not sure this solves the problem. That plastic is for reducing drafts. If you shrink it tight it will stop a draft but the surface will be just as cold as the window, and you will get condensation on the plastic itself.

If you don't shrink it tight, then the trapped air will still be humid

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Hagenaar t1_j6jz7qy wrote

A plastic film acts like an extra pane in a multipane window. Even though it's just air trapped between plastic and glass (not argon) the added space acts as an additional insulation layer.

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pilotdog68 t1_j6k9agn wrote

But that is only if you don't shrink it tight. If you do, the plastic is in contact with window, no air gap right?

So you would want to shrink it some but not all the way, and preferably seal it with dry air inside or else you'll just get condensation inside the plastic.

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Hagenaar t1_j6kasq0 wrote

We're talking about different products I just realized.

Consumer install window film is stuck on with two sided tape to the inside of the frame. This creates a gap from the windows which are recessed from the plane of the wall surface. You put the plastic over the window trim like so.

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brainwater314 t1_j6k3333 wrote

I don't think these trap air. Instead, I think it has to do with the "impedance mismatch" between the glass and plastic making the heat not conduct as well. Put simply, heat doesn't conduct well between different materials. Imagine one material is a bunch of marbles bouncing around, and another is a bunch of bowling balls bouncing around. The energy wouldn't transfer well when the marbles and bowling balls hit each other.

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Pleasant_Carpenter37 t1_j6k5qj9 wrote

They do trap air. You tape them to the frame, so there's an air layer between the window pane and the plastic.

It sounds like you're describing something that you'd stick directly to the glass. That's another option, but AFAIK it helps less than the air-trap type of plastic sheeting.

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Hagenaar t1_j6k5hz3 wrote

Plastic film works the same as a glass storm window. There is an element of a physical substance separating the warmer and cooler air, but it's largely the trapped air because it conducts heat so poorly, it's an invisible heat blanket.

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