Plastic window insulation

Cut your home heat losses in a matter of minutes

Plastic window insulation can cut a major source of home heat loss in a matter of minutes. These kits are inexpensive – as little as a dollar per window if you buy the larger kits – and you can cover a window in a quarter hour once you get good at it.

The plastic window covering seals off the indoors from outdoor drafts, adds a layer of still air between the window glazing and your living area, which improves insulation, and will give you a full heating season of comfort. And if properly installed, these window kits are virtually unnoticeable.

In this article I’ll cover the following plastic window kit topics :

• Benefits of plastic window kits
• Product selection and alternatives
• Preparation: before you install plastic window insulation
• Applying window insulation plastic
• Touch-up after installation
• Removal and reuse

Benefits of plastic window insulation

The main benefits of plastic window insulation are reduced heating bills, reduced drafts, increased comfort, and better visibility due to the smooth, transparent plastic.

These kits are great for renters, or for people on a tight budget. If you live in an apartment or a rental house, you can’t exactly pay to have old, drafty windows replaced with brand new energy efficient windows. But for a few dollars a window and a few minutes of work, you can get almost as much energy savings out of plastic window insulation.

In a moderately cold climate, a 2×3 foot window can save you about $6-8 in heating costs, if you heat with natural gas. If you use an electric heater you’ll save perhaps double that per window. For a half dozen larger windows you could be looking at $100 or more in savings per winter.

Plastic window insulation can reduce drafts from leaky windows, although you’ll get better overall results (in terms of comfort and energy savings) if you first reduce the drafts from your windows (see under Preparation below). I remember the 100-year-old wooden house we rented in Ohio for three years: we had 7-foot-high windows with no storms and no weatherproofing; these window kits made a huge difference in the winter. When the wind gusted outside, instead of feeling cold blasts of air in our living room, we got to sit in warm comfort and watch the window insulation bulge a little bit before settling back into shape!

Finally, with the shrinking plastic window insulation I’m talking about here, you can see very clearly out your windows – in many cases you can barely tell the plastic is installed, except that you might see interior lights reflected in both the shiny plastic and the window glass. These kits are much better than buying regular plastic sheeting and trying to stretch it tight by hand, because the heat-shrinking property of the insulation (activated with a blow dryer) makes them completely smooth and wrinkle-free.

Plastic window insulation can be cleaned by dusting with a dry cloth or feather duster, and if you’re careful when you take them down you can save the plastic (but not the tape) for the next winter too!

Product selection and alternatives

Before we go into specific products it’s important to distinguish between plastic window insulation and energy efficient window film, which is a semi-rigid reflective plastic film you press against window glass to reduce radiant heat transfer. While plastic window insulation provides a layer of still air between your room and the window pane, insulating window film attaches directly to the glass and acts as a reflective shield, preventing infrared radiation (heat) from passing through the glass. This keeps your house warmer in winter and cooler in summer, but it does so by reducing direct heat radiation, not by creating an insulation barrier. (Window film is more like putting sunglasses on a window, while plastic window insulation is more like a winter jacket.) The term “insulating window film” can in theory refer to either plastic window insulation or reflective plastic window film. On this page I’m only referring to the window insulation kits.

I got so caught up in putting plastic window insulation on my Ohio rental home that I bought a couple of 4′ wide rolls 50 feet long, and separate rolls of tape. (After all I had about 8 windows that were 3 x 7 feet each, so I needed a lot of plastic!) I haven’t seen the plastic rolls lately; mostly you buy kits in which there is either one large sheet of plastic or several smaller sheets.

Plastic window insulation is kind of like Saran Wrap. It doesn’t stretch like Saran Wrap but you can get the same smooth, wrinkle-free look you get with Saran Wrap once you apply heat to the product.

You can buy these window insulation kits it at most hardware stores, building supply centers, or online.

In terms of plastic window insulation brands, I recommend you stick with 3M products. In my experience their product is top quality. There are other brands that are cheaper, but they don’t tend to work as well: the plastic rips too easily, or the tape doesn’t stick to the plastic.

Avoid Duck brand products when buying a plastic window insulation kit. Apparently the plastic doesn’t stick to the tape – many reviewers have complained of this problem, although this doesn’t always mean the tape or plastic is at fault – sometimes faulty or hasty installation is the cause!

Frost King window kits get mixed reviews; by and large people like this Thermwell window insulation but some have complained of the plastic not sticking to the tape (again, hasty installation could be the problem).

You don’t have to use the heat-shrink plastic – regular clear plastic will also work but won’t look as good. For windows in rooms you’re not using much (or don’t care about the aesthetics), even opaque plastic is okay. I was able to find completely clear plastic at my hardware store that I stapled to the outside window frame, then taped around; if you staple it the same way you’d stretch a canvas over a picture frame, starting from the center of each edge and working your way to the corners, you can get an almost wrinkle-free look.

Preparation: before you install plastic window insulation

There’s nothing worse than spending 15 or 30 minutes installing your plastic window insulation, only to watch it peel off or sag within hours or days of installing it, or find that it doesn’t actually do much to keep the cold out. So make sure you prepare things properly first.

If the window itself is very leaky, with gaps between the window and frame (or the movable sash window and the fixed sash window), do what you can to seal those air gaps, before applying the plastic window insulation.

For example, you can buy removable caulking to apply around the movable part of the window to seal it against drafts; the caulking can be peeled off in the spring after you remove the plastic window insulation.

If your window glazing is held in place by putty and the old putty is cracked or missing in places, put on some new putty – it will make a big difference in keeping out the cold air.

If the trim around your windows is latex semi gloss or high gloss paint, or old varnish, be forewarned that the double-sided tape used to hold the plastic to the window frame may peel some of the paint or varnish off when you remove it.

Make sure you clean your windows before you cover them up in plastic for 3-6 months. It’s not much fun doing a perfect job on the plastic window insulation only to discover that what you see through it is dirt and grime on your glass panes. The same applies to the window frame itself: make sure it’s very clean and dry, otherwise the double-sided tape won’t stick.

Finally, make sure you remove all window coverings (drapes, shades, blinds) before you put the plastic on. You can replace them after completing the installation.

Application

There are four basic steps to applying plastic window insulation:

1. Preparation (as mentioned above): clean the window and window frame, remove window coverings
2. Place the double-sided tape around the four edges of the window frame
3. Cut the plastic, remove the backing from the double-sided tape, and apply the plastic to the sticky tape
4. Cut away the excess plastic and blow-dry the plastic to shrink it to a perfect smoothness.

This set of drawings illustrates the basic steps of installing plastic window insulation:

Here are a few general pointers to keep in mind.

Deep window sill: If the bottom of the window is a sill that protrudes a lot, you can put the tape on the top surface of the sill (facing up instead of into the room), but this means you should nail a 1/2 x 1/2″ piece of wood over top of the tape once the tape and plastic are in place – otherwise when you shrink the plastic with the blow dryer it will pull it off.

Cutting the plastic: Remember the old adage: measure twice, cut once. I recommend measuring all windows before you start, and working out on paper how the amount of plastic at your disposal can be used most efficiently. When cutting, if you need to put the plastic on a flat surface to measure and cut, make sure you lay it out on a clean surface. Remove dust, dirt, animal hair/fur etc. from the surface first. You can’t clean the outside edge of the plastic once it’s up on the window!

Applying the tape: Double-check that the window frame is dry. The tape is transparent so you can apply it directly to the front of the window frame. By window frame I’m referring to the trim (usually wood) that is installed over top of the wall. You don’t want to apply the tape directly to the wood or plastic frame of the window itself, because this won’t seal off the drafts that come through gaps between the moving and fixed parts of the window.

Don’t leave gaps between the horizontal and vertical lengths of tape. And make sure you leave the white backing on the tape until the plastic is ready to go on.

Hanging the plastic: Remove the tape backing from the top of the window frame; apply one corner of the plastic, and stretch the other corner of the plastic holding it slightly away from the tape, then slide your hand along from the applied corner to the second corner until the plastic is completely held against the tape.

Then remove the bottom tape backing, pull down on the plastic, and apply from the center part of the plastic sliding out towards one corner, then again from the center to the other corner. The idea is to get as many of the wrinkles out up front as possible; this will mean less blow-drying later.

Remove the backing on the left hand length of tape, and pull the left edge of the plastic slightly to the left and apply; continue pulling taut as you slide up or down and press in place. Repeat this for the right hand side.

Blow-drying to shrink the plastic: Don’t start blow-drying your plastic window insulation until the adhesive tape has been on the window frame for at least 15 minutes. Otherwise the bond may not develop properly with the window frame and the blow drying will pull parts of the tape loose. Ideally you should not even apply the plastic until the tape has been on the window frame for 15 minutes but I’ve never been patient enough to wait that long!

Hold the blow dryer a few inches from the plastic. If you hold it very close (because holding it further back doesn’t seem to warm it enough to cause the shrinkage you’re after), keep moving the blow dryer around. If you aim it at one area for too long and hold it right up to the plastic you risk (A) shrinking one area too much, which will make it hard to get a perfectly smooth look, and (B) burning a hole right through the plastic. I’ve done this a few times and unfortunately when that happens you don’t have much choice but to rip off both the plastic and the tape, and start over.

Trimming: Use a razor blade or utility knife to trim off the excess plastic outside the tape edges: hold the blade flat and just away from the picture frame, and pull the plastic out; slice through the excess plastic and pull away.

Touch-up later

Over time some of your plastic window insulation may sag or wrinkle. This is usually easy to fix by getting the blow dryer out again and blow-drying until the wrinkles or sags go away. You can also remove dust and animal fur with a feather duster or a cloth. We had a shedding dog when we had plastic window insulation on our seven-foot-high windows; I found the dog hair stuck to the bottom part of the windows but could easily be wiped off.

Be forewarned that cats or dogs who were used to jumping up onto or against the window or sill are liable to rip the plastic with their claws, or at least be in for a surprise when their head hits the plastic!

Removal and reuse

If you are careful about removing the plastic – if you carefully peel it off and fold it up at the end of the heating season – you can often reuse the plastic the next year. I usually found that each year when I removed the plastic I lost a little – due to tears, or the fact that I trimmed the plastic down to size after installing – so the plastic from the big windows for one year became the plastic for the medium-sized windows the next year, and the plastic from the medium sized windows progressed to the smaller windows.

Of course you can also start by putting the tape on the outside edge of the window frame the first year, and then each subsequent year moving the tape a little further in, according to how much plastic you have left.

You can reuse the plastic 2-4 times before it starts to get too brittle to use again. Also, the more shrinkage from blow-drying each year, the less shrinking capacity it has left, which is why you want to stretch it tight before you start blow-drying it.

Plastic window insulation rips easily when removed so go about removal slowly if you’re planning to use it again the next heating season.

* This article was originally published here