Inspired by this thread, I’ve got a related question. My roommate and I are getting ready to perform our annual fall ritual of covering the windows of our 100-year-old rented house with plastic sheeting.
Somebody in the other thread mentioned that putting up the plastic isn’t done to stop heat from radiating out, but to stop drafts. With that in mind, is there then any point to putting the plastic on windows that don’t open (I’m referring to windows that were never designed to open in the first place, not to “painted shut” windows)? IOW, are we talking strictly about drafts caused by cold air leaking through gaps around the windows, or do we include “convection” drafts caused by cold air on the inside of the cold glass falling and creating an indoor breeze?
This is the first house I’ve ever lived in where this was “necessary”, so I’m admittedly ignorant on the topic. My roommate, who has lived here longer than I have, doesn’t have any explanation beyond “it saves money” (though I suspect he believes that the plastic is insulating the windows). Is this actually saving us any money, or are we wasting time, plastic and money by tacking the stuff over the windows?
There can be some air leakage around the frame of the window, particularly in older structures if the wall insulation has settled.
Even for non-opening windows, drafts can get through the framing, jamb and sill. Plastic will help this if the plastic goes all the way around the trim and seals air-tight to the wall.
You could just do all the windows except one, and see if it’s noticeably cooler in front of that window than the others.
I remembered reading something a long time ago about how insulation works to create an air pocket of sorts that reduces heat transfer, so a quick search turned up this, which while barely relevant does include the line:
I imagine the purpose of the plastic is to do as you indicated and prevent drafts by convection by creating a relatively stable and still air pocket between the window and the room. I think there’s also something to do with plastic not transferring heat as well as glass, so the surface of the plastic won’t cool down the air immediately to the inside to the extent that glass does.
We use plastic on the windows and yes, the big advantage is to stop drafts. I can usually feel the difference as soon as the plastic is put up.
At the same time, the air space between the window and the plastic does act as an insulator. It does trap the air and slow down heat transfer, though that isn’t as noticeable as when it’s preventing a draft.
