Plastic window film looks like a mess until you have done it once. Then it becomes a quiet hour and a warmer spot by the window, with a draft you can stop feeling on your ankles. The job is simple: clean, measure, tape, shrink, trim. The trick is doing each window in one sitting so the film does not sit half-done while the cold keeps coming in. Your father will probably say the draft is all in your head. Let him say it, then measure the window anyway.

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Check the window before you cut anything

Open every window you plan to cover. Film seals the window shut, so keep at least one bedroom window free of film and make sure it opens easily. Check that the latch works and that the sash is not painted shut. If a window is stuck, deal with that first.

Gather the kit

You need window insulation film sized for the window or a roll you can cut, double-sided tape made for the film kit, a sharp utility knife with a fresh blade, a metal straight edge, a measuring tape, a hair dryer on its lowest setting, a clean cloth, and a bucket of warm water with a little dish soap. Buy the kit with its tape, not the film alone, because the tape decides whether the film stays up.

The steps, in order

  1. Clean the frame and glass with the soapy water and dry them completely. Dust and grease are what make tape let go.
  2. Measure the glass from inside the frame, width and height. Cut the film about an inch larger on every side so you have something to trim.
  3. Apply the double-sided tape to all four sides of the frame, pressing it down firmly. Leave the paper backing on until you are ready to fit the film.
  4. Peel the backing from one side of the tape only. Lay the film across the window and press it onto the top tape first, then work it down to the sides. Keep it taut, not stretched.
  5. Peel the backing from the remaining tape and press the film into place. Leave it loose at this stage. Do not pull it tight yet.
  6. Hold the hair dryer on low, a few inches from the film, and move it slowly across the surface, starting in the middle and working outward. Keep it moving. Heat held in one spot can warp the film or lift the tape. The film tightens and goes smooth as it warms.
  7. Let it cool, then trim the excess with the utility knife against the straight edge, cutting along the outside of the frame.
  8. Test it. Hold your hand near the window and feel for cold air. Look for lifting corners and check that the film stays flat once the room is warm.

After it goes up

Check the tape corners every so often, especially after a cold snap or a stretch when the house gets very dry. Press any lifted corner back down and add a small piece of tape if needed. In the spring, do not peel the film off in a hurry. Warm it slightly, peel slowly, and clean the tape residue off the frame before the next window goes up.

When to call someone else

If a window is cracked, the frame is rotting, or the window will not open or close at all, have it looked at before you add film. Film is a stopgap for drafts, not a repair for a failing window. If a gas appliance shares the room, ask the person who services it whether sealing the windows affects its air supply.

What to do tonight

Put your hand flat near each window in the house and note the one that feels coldest. Start there. Leave the rest for another evening.