Buying Guide
Best Window Insulation Film UK 2026
Updated August 2026
Window insulation film is the cheapest form of secondary glazing. For £12–18 per window, you create an insulating air layer that mimics double glazing — reducing heat loss by up to 50% on single-glazed windows. It is completely renter-friendly (removable velcro attachment), invisible from outside, and takes 15 minutes to fit. If you have single-glazed or poorly-insulated windows, this is the highest-impact upgrade for the lowest cost.
Quick answer
Our top pick: BKSAI Velcro Window Film / Duck Brand Shrink Film
£12 – £18 per window on Amazon
Best reusable: BKSAI Velcro Window Film (£12-18, remove in summer, reuse next winter). Best budget: Duck Brand Shrink Film (heat shrink, tighter fit). Both reduce heat loss by 40-50% on single glazing.
Check Price on Amazon →How window insulation film works
Film does not insulate because the plastic is thick — it is a few microns. It works because of the sealed pocket of still air it creates between itself and the glass. Still air is a genuinely good insulator; that is exactly how a double-glazed unit works, just with a 16mm cavity instead of a 20mm one.
- Cuts conduction. The trapped air layer slows heat moving from the room to the cold glass.
- Kills convection currents. The cold downdraught that rolls off a single-glazed window and across the floor stops almost entirely.
- Blocks frame draughts. The perimeter seal covers the gaps around old sashes and casements at the same time.
- Raises the surface temperature. The film sits several degrees warmer than the glass, which is why condensation stops forming on it.
Single glazing has a U-value around 5.0 W/m²K. Add film and you're nearer 2.8–3.0 — not as good as modern double glazing (1.2–1.6), but a 40–50% improvement for about £15.
The best window insulation film in the UK
BKSAI Velcro Window Insulation Film
The sensible default. Being able to peel a panel off to open the window on a mild day — and put the whole thing away in April — makes it far more livable than a shrink-fitted sheet, at a similar cost per season.
Pros
- Velcro mounting — remove in spring, refit next winter
- No heat gun or hairdryer needed
- Can be opened to vent the window
- Lasts three to five seasons
Cons
- Slightly visible velcro edge
- Not quite as taut as shrink film
Who it's for: Renters and anyone who wants the window usable in summer
Check Price on Amazon UK →Duck Brand Heat Shrink Window Film
If the window stays shut all winter, shrink film gives the better result. Warm it with a hairdryer and the wrinkles vanish completely — from a metre away most people won't notice it is there.
Pros
- Shrinks drum-tight — almost invisible when fitted
- Best thermal seal of the two types
- Covers several windows per pack
- The long-standing benchmark product
Cons
- Single season — cut away in spring
- Tape can lift old paint on removal
Who it's for: Windows you won't need to open until spring
Check Price on Amazon UK →Deconovo Thermal Curtains
Film plus thermal curtains is the combination that actually transforms a cold, single-glazed room. The film handles the daytime heat loss, the curtains take over at night when the temperature difference is greatest.
Pros
- Adds a second insulating layer over the film
- Triple-weave lining blocks the remaining draught
- Also cuts noise and light
- Wide range of drops and widths
Cons
- Only works when closed
- Needs a decent pole or track
Who it's for: Stacking with film for the biggest single-glazing improvement
Check Price on Amazon UK →Reusable vs shrink film
| Velcro (reusable) | Heat shrink | |
|---|---|---|
| Cost per window | £12–£18 | £4–£8 |
| Lifespan | 3–5 winters | 1 winter |
| Appearance | Slight edge visible | Near invisible |
| Can open the window? | Yes | No |
| Tools needed | None | Hairdryer |
| Renter safe | Yes | Test the tape first |
Step-by-step fitting guide
- Clean the frame. Wipe the frame with methylated spirit and let it dry — tape and velcro both fail on dust or grease.
- Measure and cut. Measure the frame opening and cut the film 3–4cm oversize on every side.
- Apply the tape or velcro. Run it around the full perimeter of the frame with no breaks. A gap anywhere means no sealed air pocket.
- Attach the film. Start at the top, work down, keeping light tension. Small wrinkles are fine at this stage.
- Shrink it (shrink film only). Hairdryer on medium, 15–20cm away, moving constantly from the centre outwards until it's drum-tight.
- Trim the excess. Run a sharp blade or scissors along the outer tape edge.
- Check the seal. Hold a candle near the perimeter — no flicker means the pocket is sealed.
Fit on a dry day. Trapping damp air in the pocket is what causes misting between film and glass.
Window film vs secondary glazing vs double glazing
| Insulation film | Secondary glazing | Double glazing | |
|---|---|---|---|
| Cost per window | £12–£18 | £150–£400 | £400–£800 |
| Heat loss cut | 40–50% | 50–60% | 65–75% |
| Fitting time | 15 min DIY | Half a day | Installer, 1–2 days |
| Renter friendly | Yes | Rarely | No |
| Noise reduction | Minimal | Good | Good |
| Payback | First winter | 8–15 years | 15–25 years |
Per pound spent, nothing else in home heating comes close. Film delivers most of the benefit of secondary glazing for around a tenth of the price.
Does window film stop condensation?
Mostly yes, and for a specific reason: condensation forms on the coldest surface in the room. Film sits in the warm room air rather than against the outside, so its surface temperature is several degrees higher than the glass — usually above the dew point, so water no longer forms there.
Two caveats. If the perimeter seal has a gap, humid room air leaks into the pocket and condenses on the glass where you can't wipe it. And film does not remove moisture from the room — if humidity is high, it will simply condense on the next coldest surface instead, often an external wall behind furniture.
Pair film with proper moisture control: how to stop condensation on windows →
Window film for renters
- Choose the velcro type — it removes without touching the paintwork.
- Test any adhesive on a hidden corner of the frame first, especially on old gloss.
- Nothing is drilled or permanently altered, so no landlord permission is normally needed.
- Film is invisible from outside, so it won't breach a leasehold or conservation restriction.
- Take it with you when you move — it's your property, not a fixture.
- Warm the tape gently with a hairdryer before peeling to lift it cleanly.
Buying advice
Only worth it on single or failed glazing
Tip
Fit on a dry day and seal the full perimeter
Warning
Don't film over a room's only ventilation
Frequently asked questions
Bundle
Cold Window Kit — Film plus thermal curtains
- BKSAI velcro window film£15Amazon →
- Duck Brand shrink film£12Amazon →
- Deconovo thermal curtains£35Amazon →