The short answer

Film works on a window you will not open all winter, with a clean, painted or finished frame that tape can grip and release from, in a room without an existing moisture problem, and with permission if you rent. Patch-test the tape on a hidden spot first. Measure each window with a margin, then buy the pack whose sheets or rolls actually cover your sizes; the kit comparison does that arithmetic.

First, which bill would this change?

Film reduces drafts and heat loss through the window. That saves whatever fuel heats the room. If your heat is gas, oil or propane, a sealed window mainly shows up on that bill; the electric bill sees only the smaller knock-on effect of the furnace blower, circulator or controls running a little less. If you have electric baseboards, a heat pump or an electric furnace, then yes, it can lower the electric bill. Either way we cannot tell you by how much; that depends on the window, the weather, the thermostat and the rest of the house, and we have not measured it. If your real question is "why did my electric bill jump", start with the diagnostic before spending on film.

The decision tree

  1. Do you have permission?
    • Owner: yes, move on.
    • Renter: check the lease for anything about window treatments or adhesives, and ask in writing if unsure. Film is temporary, but tape can mark paint, and that is what deposit disputes are made of. Keep the reply.
  2. Will you need to open this window before spring?
    • Yes, for ventilation, a window AC unit, a fire escape, or a cat: skip this window, or accept that you will be re-taping it. Never film a window that is a required emergency exit without being able to remove the film quickly.
    • No: continue.
  3. Is the frame finish one the tape is designed for?
    • Clean, dry painted wood or vinyl (both manufacturers), metal (Frost King) or aluminum (Duck), in sound condition: continue, but patch-test.
    • Wallpaper, wallboard, plaster or veneer: Frost King's sheet excludes these. Our own added caution: also skip unfinished, flaking or freshly painted frames, where tape is likely either not to stick or to take the finish with it.
  4. Is there condensation, mold or rot on the window already?
    • Yes: fix the moisture source first. EPA's guidance is to address the source of moisture; a film layer can trap it against the frame.
    • No: continue.
  5. Can you physically reach all four sides of the frame?
    • Behind a radiator, a built-in, or above a stairwell: measure whether you can apply tape and use a hair dryer on every edge. If not, that window is not a film candidate.
  6. Patch test.
    • Stick a short piece of the kit's tape on a hidden part of the frame, leave it a day or two, then peel it slowly. If paint lifts, stop. This is the only way to know how your particular finish behaves; no manufacturer promises "damage-free" for every paint, and neither do we.

Frame finishes that tolerate tape, according to the manufacturers

Two of the three kits we compare publish surface guidance. They agree closely:

  • Frost King: Clean, dry, grease-free metal, painted wood or vinyl; not wallpaper, wallboard, plaster or veneer.
  • Duck: Clean, dry painted or finished wood, aluminum or vinyl.
  • 3M: the instruction sheet for the exact five-window pack was not available to us, so follow the sheet in the box.

A finish that sounds similar is not the same finish. "Painted wood" that is 40 years old and chalky will not behave like a fresh enamel, which is why the patch test is in the tree above and not in a footnote.

Measuring a window for film

Measuring a window opening with a taped margin A window opening 36 inches wide by 60 inches tall, drawn inside a film rectangle 38 by 62 inches. The tape runs on the frame around the glass, and the film extends one inch past the tape on every side. Film cut to 38 × 62 in. (dashed): opening plus 1 in. each side Tape on the frame (orange): where the film is attached Opening 36 × 60 in. measured between the tape lines Use your kit's own margin instruction; it may differ.
Illustrative example of the arithmetic. Measure where the tape will go, then add the margin your kit's instructions specify on every edge. Film is trimmed after shrinking, so err large.
  1. Decide where the tape will sit. It goes on the flat part of the frame around the glass, not on the glass and not on a moving sash.
  2. Measure the width and height between those tape lines. Measure twice; old windows are rarely square.
  3. Add the margin your kit specifies on every edge. In the example, a 36 × 60 in. opening with one inch extra each side needs a 38 × 62 in. piece of film.
  4. Write each window's cut size down, then check it against the sheet or roll dimensions in the kit comparison. The example 38 × 62 in. piece fits a 42 × 62 in. sheet with 4 in. spare across and nothing spare in length; a taller window, or one where you want a cutting allowance, needs a roll kit instead.

Installing, in outline

Every kit's sheet has its own steps and they differ in detail, so follow the one in your box. The common shape of the job, which is all we will describe here:

  1. Clean the frame with a mild cleaner and let it dry fully. Tape does not stick to dust or damp.
  2. Apply the double-sided tape around the frame, pressing firmly, and remove the backing.
  3. Cut the film to your marked size, lift it onto the tape starting at the top, and pull gently taut as you go round. Do not chase every wrinkle now.
  4. Shrink with a hair dryer on a moderate setting, moving continuously, starting at the corners. Wrinkles pull out as the film tightens.
  5. Trim the excess with a sharp blade, cutting away from the tape.
Do this in daylight with the heat on

Tape and film behave better on a warm, dry frame. Do not seal a window over visible condensation. If the room is humid enough that the glass fogs, deal with the humidity first, or the moisture ends up between the film and the window.

Removal, and what "removable" actually means

In spring, peel the film off, then peel the tape slowly at a low angle. Manufacturers describe their tape as removable, and on a sound finish it usually is. What no manufacturer promises is that it will come off every paint in every condition without a trace. The realistic outcomes on an old frame are: clean, a faint line where the tape kept the dust off, a little adhesive residue, or lifted paint on a finish that was already failing. A patch test can reveal an immediate problem with your finish; it cannot promise how the tape will come off after a whole winter. If residue is left, warm it gently with the hair dryer and roll it off with a finger before reaching for solvents that may themselves mark paint.

For renters, take a photo of each frame before and after. It is cheap insurance for the deposit conversation.

Doing nothing, or nearly nothing

Film is not always the right answer, and it is never the first one:

  • Lock the window. Old sash locks pull the sashes together and close the gap between them. This is free and often the biggest single draft on a double-hung window.
  • Close curtains or blinds at night and open them on sunny days. Existing curtains do part of the job of film for nothing.
  • Find the draft first. Hold a damp hand or a strip of tissue near the frame on a windy day. Many "window drafts" come from the gap between the frame and the wall, or under the sill, which film over the glass will not touch and a bead of removable caulk or rope caulk will.
  • Rope caulk or removable sealant in the sash gaps is cheaper than film for a window whose problem is air leaks rather than the glass itself.

If after that the window still feels cold to stand near, or you can see the curtains move, film is a good next step, and the comparison below is where to choose one.

Before you order a kit

  • Permission in writing if you rent Tape can mark paint; a written yes prevents a deposit argument.
  • The window stays closed until spring Film seals the sash; opening it means starting over.
  • Frame is clean, dry painted wood or vinyl (metal or aluminum only as your kit's sheet allows), and the patch test passed Frost King: Clean, dry, grease-free metal, painted wood or vinyl; not wallpaper, wallboard, plaster or veneer. Duck: Clean, dry painted or finished wood, aluminum or vinyl.
  • No existing condensation, mold or rot on the window EPA: fix the moisture source first. Film can trap moisture against the frame.
  • You can reach all four edges with tape and a hair dryer Behind a radiator or above a stairwell may rule the window out.
  • Each window's cut size fits the kit's sheet or roll Measure with margin; a 42 × 62 sheet cannot cover a 40 × 62 opening properly.
  • Your heating fuel is the bill you wanted to reduce Film saves the fuel that heats the room.

Ready to choose a kit? Compare the 3M, Duck and Frost King packs by real coverage.

Sources and evidence

What we are relying on

Frost King's instruction sheet calls for clean, dry, grease-free metal, painted wood or vinyl, and excludes wallpaper, wallboard, plaster and veneer.
Verified from the manufacturer or official document.
Duck's rolled-kit guidance names clean, dry painted or finished wood, aluminum or vinyl as suitable frame surfaces.
Verified from the manufacturer or official document.
EPA guidance is to fix the source of a moisture problem. Sealing a window does not resolve an existing moisture issue.
Verified from the manufacturer or official document.
3M's 2141W-6 kit is specified for five windows of up to 3 ft × 5 ft.
Verified from the manufacturer or official document. Exact packaged installation instructions were not located; model-specific steps are withheld.

What this page does not establish

  • No installation or removal trial has been performed by us on any finish; the removal outcomes described are possibilities to test for, not results.
  • No energy saving figure is given because none has been measured.
  • The installation outline is generic; the instruction sheet in your kit takes precedence, and the 3M five-window pack's sheet was not available to us.

Sources

  1. Indoor shrink window kit instruction sheet, Frost King. Manufacturer document; read 2026-09-07.
  2. How to install rolled window kits, Duck Brand. Manufacturer document; read 2026-09-07. Family procedure for rolled kits; not a model 288070 boxed sheet.
  3. A brief guide to mold, moisture and your home, U.S. Environmental Protection Agency. Official guidance; read 2026-09-07.
  4. 3M Indoor Window Insulator Kit 2141W-6 product record, 3M. Manufacturer document; read 2026-09-07. Five 3 ft × 5 ft windows. The exact packaged instruction sheet was not located, so model-specific installation steps are not quoted.

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