I have some windows that I want to insulate at night during the winter. I have energy star windows, thermal drapes, and cellular blinds and those plastic window film kit things, but I want to reduce my heating costs even more.

From my quick googling it looks like there is some danger in insulating "too well" from the inside, namely that I could end up with the window getting too cold and getting damaged by water or other thermal stuff. If that's wrong, please let me know and ignore the rest of this question.

If that's right, then I'm wondering what I can do to insulate my windows further while avoiding this issue. To me it seems intuitive to try and insulate my windows from the outside, ideally in a way that I can "turn off" during the daytime. Any ideas of how to do this? Maybe some kind of fancy shutters?


  • Why 2 Q’s on same topic? Sep 4, 2020 at 21:02
  • Busted! My thought was to have one question about insulating from the outside and one about fiberglass. I duplicated the first paragraph between the questions since the "baseline" conditions are the same. By the way I really appreciated your feedback on the other question!
    – capet
    Sep 4, 2020 at 21:09

2 Answers 2


Fit shutters, been “standard” on chalets in Switzerland for over 200 years.

You could make the shutters perform even better by making them with an insulation layer as well. Fitted well that would start to get closer to the r value of the wall.

  • Thanks a lot! I am not very handy, so do you know of any standardized versions of what you are describing? Also, do you have any advice as to how to find installers who would build something like this for me? Maybe some "keywords" to look for?
    – capet
    Sep 8, 2020 at 17:22

I always strongly recommend the 3M plastic insulation kits. One of their main products is transparent tape and that is what fails with other brands.

Insulating too much might mean you are risking condensation between layers or similar. In the winter the air is dry enough for this to be unlikely. I have never seen it. The kits come in Inside and Outside varieties but the inside is the easiest to use.

During a snow storm in Chicago that came to be known as Snow-pocolypse my 3M plastic held up. The wind was so strong against my balcony that the plastic was distended from the window over 1 foot. I stacked boxes against it to take the strain off. I've had similar storms since but the 3M has never failed.

On windows without plastic I can feel the cold, not the wind, move right through.

  • Whoa sweet, thanks a lot!! So just to practice "active listening," let me make sure I understand you correctly: 1. You have used the outside kind and that held up during snow-pocalypse? 2. You're saying the inside kind is probably fine as far as condensation, because winter is dry enough in the midwest?
    – capet
    Sep 4, 2020 at 20:51
  • @Carpet Thanks. I have only used the Inside kind. This is easier since it goes from floor to six feet up. Outside you might need a ladder to get to the window's bottom and top. I am always in rooms on the 3rd or 5th floors. Plastic stuck to the house would not be as strong as the windows and trim already there. Inside there is less weather to tear it off. I have never had condensation within the space.
    – Elliot
    Sep 6, 2020 at 18:41
  • Aha! So I guess that means you speak on the basis of your own experience when you say that you don't think condensation would be a big issue when insulating from the inside to moderate levels, at least in Chicago?
    – capet
    Sep 8, 2020 at 17:23

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