OK to insulate windows with regular plastic sheeting?

November 29, 2011 11:47 PM

Will black plastic sheeting insulate my windows as well as the commercial shrink-wrap stuff? I've used window insulator kits like this and they work great. I was wondering if I could skimp. First, would any plastic do as well? I already use this stuff to block light while I sleep. If that's not as good, is there something special about shrinking the commercial kit plastic with a hair dryer, or is that just for looks? I'd rather not borrow one every year.
posted by Noumenon to Home & Garden (14 answers total)

Shrinking the clear plastic gives you an unwrinkled view out the window. It's the trapped air that insulates, so black plastic should work just as well if you don't want transparency.
posted by weapons-grade pandemonium at 11:58 PM on November 29, 2011 [1 favorite]

You know hair dryers are $2 at thrift stores, right?
posted by weapons-grade pandemonium at 12:00 AM on November 30, 2011 [1 favorite]

well, shrinking the plastic also gives you a tight seal between the plastic and the window-frame, and making sure there is no air movement between the insulating layer and the outside/inside is key to its insulating properties.
posted by brightghost at 12:08 AM on November 30, 2011 [3 favorites]

I think the shrinking is just for looks. If you're blacking out the window anyway it wouldn't matter.

There is an ideal size for the air gap between the window and the plastic sheeting, though— it should be as wide as possible but not so wide that the air can convect freely in there.
posted by hattifattener at 12:30 AM on November 30, 2011

The goal of shrinking isn't for looks, but to create a somewhat airtight seal, as brightghost mentions. Trapped air adds insulation, because air has low thermal conductivity, which is why windows are sold with two or three sealed panes.
posted by Blazecock Pileon at 12:35 AM on November 30, 2011

If you can pick up some bubblewrap, it's a pretty good insulator, and lets in light. And you can store & re-use it.
posted by theora55 at 3:20 AM on November 30, 2011 [2 favorites]

Yes, the trapped air is an insulator. So if you can trap the air just as well with the black sheeting, then you are probably fine. The nice thing about the shrinky stuff is that you can tape it to the wall and completely seal a drafty window. And that it isn't wrinkly.
posted by gjc at 4:42 AM on November 30, 2011

The window kits are pretty damned cheap, and, what's better, are extremely easy to install - they're designed well.
posted by KokuRyu at 4:51 AM on November 30, 2011

The window kits also provide the advantage of being designed for easy and non-damaging removal.

The shrinking is mostly for looks; it's the tape which provides the seal. If you are going black you could improve the insulation of the air gap by filling it with something to reduce convection currents. Down would be best, but oh what a cleanup. Shipping peanuts, bubble wrap, tissue paper etc. would be neater.
posted by caddis at 5:28 AM on November 30, 2011 [2 favorites]

Best answer: they're designed well

I've used numerous brands and have observed that you get what you pay for. The shrinkfilm isn't the variable; it's the quality of the adhesive tape.

It's probably possible to save more money buying bulk plastic film, but you need something really lightweight, otherwise the tape won't be strong enough to hold it up. The lightest plastic sheeting my local hardware store sells needs to be stapled or tacked to last the winter. I haven't tried anything like Saran Wrap, though, which you can get for restaurant use; it just seems too unwieldy at that size. In general, I've read that there's a good ROI on these kits, and in rooms you frequent comfort can be of no price, so I wouldn't be really aggressive about shaving pennies here: you're already shaving pennies by putting them in. Find a price point for the kits you like and one that works and stick with that.

As to the hair dryer, I bought one just for this project and use it every year. But then I tend to do a window or two every day instead of all of them at once, so it's nice to have a portable kit that's all in one place.
posted by dhartung at 8:09 AM on November 30, 2011

I use a shower curtain and packing tape. If it's good tape, you can tug it nicely tight - I've never used a blowdryer, and it still makes a HUGE difference. The shower curtain is great because it's noticeably thicker than the plastic sheeting. I've bought the kits, and I've also used the plastic painter's drop cloths you can buy in varying thickness at Home Depot/Lowes. I much prefer the shower curtains. They're more expensive, but if you take it down carefully you can use it for more than one year. First time I tried it, I spent probably ten bucks for a super-clear shower curtain at bed bath & beyond, because it's really important to me to maintain visibility out of the window in the living room. This year, I found some that are nearly as good for a quarter that price at Target.

I've used white duct tape too; and both it and the packing tape can mess up the paint. For various reasons that's not a big deal to me - but it's something to keep in mind.
posted by lemniskate at 11:21 AM on November 30, 2011

There is an ideal size for the air gap between the window and the plastic sheeting, though— it should be as wide as possible but not so wide that the air can convect freely in there.

For air the ideal gap is between 3/8ths and 1/2 an inch.
posted by Mitheral at 1:18 PM on November 30, 2011 [1 favorite]

The goal of shrinking isn't for looks, but to create a somewhat airtight seal, as brightghost mentions.

Blazecock Pileon, this makes no sense. Plastic doesn't become more airtight when taut. As caddis notes,

The shrinking is mostly for looks; it's the tape which provides the seal. If you are going black you could improve the insulation of the air gap by filling it with something to reduce convection currents. Down would be best, but oh what a cleanup. Shipping peanuts, bubble wrap, tissue paper etc. would be neater.
posted by IAmBroom at 9:25 PM on November 30, 2011 [1 favorite]

Blazecock Pileon and brightghost (& favorites): Have you ever used shrink wrap on windows? It appears you don't know what you're talking about. Unless the tape (which provides the seal) is secure, shrinking the plastic will actually loosen the seal. The shrinking is for optics.
posted by weapons-grade pandemonium at 2:19 PM on December 1, 2011