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Short version:

I am using a Frost King window insulation kit on a window. Can I skip the hairdryer step and still get a good amount of insulating effect?

Long version:

I am using a Frost King window insulation kit on a window. The way these work is that you tape a plastic sheet to your window frame (or some surface surrounding the window), then use a hairdryer on the plastic sheet to pull it taut.

My window frame is very bumpy (not a nice flat surface for me to stick the sheet onto), plus there is a window air conditioning unit sticking out in the middle (I can't take it out). Unless I want to cut the included plastic sheet into a more complex shape, the hairdryer step described above causes the plastic sheet to pull away from the tape's contact surface as it is drawn taut.

So my question is simple: Can I just skip the hairdryer step if I don't care what the end product looks like, or is the hairdryer step necessary to produce the insulating effect? Will I still get some benefit if I skip the hairdryer step?

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    Good question, and welcome to SE. I'd be happy to offer more suggestions if you care to post a photo. Maybe we can get that window nice and tight after all.
    – isherwood
    Jan 17, 2016 at 20:30
  • Try removing the window air conditioner. You're not honestly expecting to use it, and being indoors will lengthen the unit's life.
    – Harper - Reinstate Monica
    Jan 19, 2016 at 3:54
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    If you have to cut a simple penetration into the sheet but the tape fails when you shrink it, you should be able to use a stronger tape, but don't rely simply on its adhesive strength. Instead, use a tape that's resistant to stretching (eg., the metal foil tape for ducts) try wrapping tape around and around the A/C, in several continuous layers, so that it clamps down tight on itself and most of its grip comes from refusing to stretch rather than from the strength of the glue.
    – sh1
    Nov 25, 2018 at 23:33

3 Answers 3

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Tightening the transparent plastic is mainly for cosmetic reasons. As long as the tape stays in place, the plastic will do its job of preventing air flow.

If the kit is exposed to buffeting winds strong enough to snap the plastic sheet back and forth, it could tear or pull off the tape. So you want it to be as tight as possible.

In general most people find that it's impossible to pull the sheet tight without leaving a few wrinkles, but after using the right color tape and shrinking the plastic a little, the result is indistinguishable from a windowpane.

In your case, with that AC in place, you're not going to get a windowpane effect anyway, so just pull it tight manually. You might consider taping both the inside and outside to help prevent loosening or blowout.

EDIT: I have just learned of another reason for tightening a window film. The plastic film can not only eliminate through drafts, but can be installed to reduce convection transfer by trapping a thin layer of air against the glass.

The ideal separation distance between film and glass is 1/2 inch. Even 1 inch is too thick as it allows the trapped air to circulate freely within the gap. But at 1/2 inch, unless the plastic film is quite tight, it will bow in and stick to the glass over at least part of the window.

I know this remark does not apply to the OP's circumstance but I include it here for the general case.

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  • First will often get you a few more votes when the question is first asked, but quality answers get upvoted over time. Don't stress about it. And remember that upvotes don't cost you anything to give ;-)
    – Ecnerwal
    Jan 17, 2016 at 20:51
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The hairdryer step is for two reasons: To prevent noise in drafty situations, and to improve visibility and aesthetics.

If you can live without either of those, it'll work just fine.

One possible solution to your pull-away problem would be to apply the double-stick tape to the outside face of the window trim (perpendicular to the wall surface).

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    Our standard procedure with window film kits was to buy a cheap kit (Frost King might even have been the brand) and throw away its tape, then buy 3M window film tape (without their film, or kit) to get good sticky at the lowest cost - and then, as isherwood says, tape to the outside of the window frame sides, top, and bottom, going out over the windowsill to attach to the bottom of the frame. Being real cheapskates we did not trim too close, and could usually get a second year of use out of the film making use of the overage next year. But we did shrink it - otherwise it looks terrible...
    – Ecnerwal
    Jan 17, 2016 at 20:46
  • Big +1 for throwing away the Frost King tape. When it comes time to remove it in the spring, it invariably either peels the paint off the trim or leaves behind a yellowish, hard-to-remove residue.
    – Joe Shaw
    Jan 20, 2016 at 14:37
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There is an efficiency factor in pulling the plastic tight, but it may or may not be significant.

Proper thermal double glazing has a fairly specific air gap distance that is chosen to be as large as possible while being thin enough that the internal air can't establish cycles that allow convection (effectively stirring) to carry heat from one side to the other. If your plastic is in a situation where it moves frequently then the air that is trapped against the window can be moved, and that movement transfers heat.

And as another answer said; if it doesn't move but the gap becomes too thin or too thick then it will also lose efficiency.

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