Installing Plastic Insulation Film on Drafty Windows

Surface and temperature decide whether it holds

Almost every failed install comes down to the tape, not the film. Before you start, pull back the curtains, raise the blinds out of the way, and unscrew casement crank handles so the film can lie flat. The tape grips best on a clean, dry frame above about 50°F (10°C). Wipe the trim with rubbing alcohol and wait until it's dry to the touch, about 2–3 minutes. If the room or the trim feels cold, warm a 2 ft (60 cm) section with the hair dryer for about 30 seconds right before you press the tape down. Press the tape firmly with your thumb along its whole length. Most kits say to let it set for 10 to 30 minutes before the film goes on. Use that wait to clean and tape the next window instead of standing around.

• Where to tape: put it on the flat face of the indoor trim, about 1/2 in (1 cm) from the outer edge. That way the film boxes in the whole sash, including the gaps where the air actually leaks.
• No flat trim (aluminum frames, drywall returns): tape to the flat part of the window frame itself or to the wall just around the opening. On painted drywall, always use the painter's-tape layer below.
• Renters or fresh paint: lay a strip of painter's tape at least 1 in (2.5 cm) wide first, then put the double-sided tape on top of it. In spring, warm the tape with the hair dryer and peel it slowly at a low angle, folding it back on itself, so it doesn't lift paint.

Cut generous, shrink patiently

Cut the film 2 in (5 cm) larger than the taped area on every side. Peel off the tape backing one side at a time, starting at the top, and hang the film loosely. Pull it just snug enough to remove big sags, because the heat does the tightening. When shrinking, set the hair dryer on high, hold it about 1–2 in (2.5–5 cm) from the film and keep it moving. Work in this order: the edges first, aiming about 1 in (2.5 cm) inside the tape and never right on it, then the corners, then sweep the center. Heat on the tape softens the adhesive and lets the film creep loose. If you hold the dryer still or touch the film, you'll melt a hole in seconds. Spend your time on this step. A fast, hot pass leaves wrinkles that never come out.

Choosing your version

• How many windows: the steps are timed for 3 standard windows in one session. Add roughly 25–30 minutes for each extra window, and tape them in a batch so the set-time overlaps.
• Standard indoor kit: fits most double-hung and casement windows up to about 3×5 ft (90×150 cm). A typical 5-window kit covers a small apartment. In the UK the same product is often sold as secondary glazing film.
• Patio door or picture-window kit: use this for openings wider than about 5 ft (1.5 m). For those, a second pair of hands makes hanging the sheet much easier.
• Outdoor kit: only worth it on ground-floor windows where you can reach the outside frame safely.
• Reusable alternatives: bubble wrap pressed onto glass misted with water is the cheapest option and needs no tape, but it blurs the view. Custom acrylic interior inserts cost much more but press into the frame and last for years.

How to tell it worked

A good install looks almost invisible: the film is taut like a drum, with no wrinkles you can see from 6 ft (2 m) away. On a windy day, hold a strip of tissue near the trim. It should hang still where it used to flutter. A gentle bowing of the film in strong wind is normal. If an edge has pulled loose, the film will flap, so re-press it. Keep a knife handy near any bedroom window you've covered, because film can be sliced open in seconds in an emergency.