I live in an older home with windows that build up frost in the winter, which indicates they aren't insulated very well. I am thinking of installing kits like these over the windows:

Window insulation kit crystal clear shrink film

However, before I spend the time and money (and generate the additional plastic waste) I'd like to have a better idea of how effective they are.

Is there any research or studies on how effective these kits are?

I have heard lots of anecdotal evidence, so that's not what I'm interested in here.

1 Answer 1


They will help . But a word of caution ,water will be running off your window sills if you put them on the inside of the windows. They are not attractive but neater when on the outside. On the inside they insulate the window and it is colder; moisture from inside the house condenses and runs down the cold glass. When on the outside ,they make the glass a little warmer and there is no condensation. I have a garden shed /green house so it is fairly humid with some electric heaters . I found insulating the windows on the inside causes heavy condensation . Insulation on the outside causes less or no condensation on the glass. I use foil faced ridged foam panels so the insulation is greater than the subject plastic film , that makes my situation more pronounced.

  • Maybe a partial experiment to try yourself to help answer the question - some people lightly mist their windows with water and use that to stick bubble-wrap to it as an insulator. If you have some from packaging it would be a virtually free way to see if it helps - albeit at the cost of the view.
    – davidgo
    Commented Dec 26, 2020 at 3:08
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    If there is water running down the window then there is airflow into the cavity formed by the kit. The kits are meant to be installed to seal off the cavity so there can be no airflow. No doubt achieving a seal depends on the particularities of the window involved but it is possible in some cases. In cases where it is not possible, indeed, do not use these kits. The condensation is not only unsightly and annoying, it is a mold and rot hazard. Commented Jan 24, 2021 at 23:47
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    You can not reasonable seal the plastic sheet. Cryogenic facilities go to great lengths to seal foam insulations with little success , moisture (air ) will get in someplace. Commented Jan 25, 2021 at 17:01
  • More usefully: seal the top and sides very carefully, and have a (small) gapo at the bottom. That way as air folws in and out it's at least at the bottom and water will flow out. I get condensation on the outside of my double glazed windows as well as on the walls so it seems inevitable that it will happen somewhere.
    – Móż
    Commented May 25, 2021 at 0:35

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