Best Window Insulation Film UK 2026: 3 DIY Secondary Glazing Kits

Best window insulation film UK 2026: quick picks

Specifications and availability were checked in September 2026. Prices and stock change frequently, so measure your windows first and compare coverage rather than judging only by pack price.

How we chose these window insulation films

AurumPick has not laboratory-tested these kits. We compared current manufacturer and UK retailer information for film dimensions, coverage, fitting method, included tape, suitability for single glazing and current availability.

We deliberately excluded privacy film, solar-control film, safety/security film and generic marketplace products with unclear specifications because they solve different problems or are difficult to verify consistently.

Energy Saving Trust describes plastic secondary-glazing film as a low-cost DIY option but also says it provides the least thermal benefit of the secondary-glazing choices and is less durable than rigid magnetic or permanent systems. That sets an important expectation: these kits are temporary budget measures, not substitutes for proper secondary or double glazing.

1. tesa INSULATION Film — best overall

Best for: single-glazed windows where you want a clearly documented DIY kit from an established manufacturer.

tesa describes its INSULATION Film as a transparent secondary layer for single-pane windows. The film is fixed on the inside using included double-sided tape and tightened with warm air from a hairdryer. Current UK listings show both a 1.7m × 1.5m version, covering 2.55m², and a larger 4m × 1.5m version, covering 6m².

• Designed specifically for single-pane windows.
• Transparent shrink-film installation.
• Double-sided fixing tape included.
• Hairdryer-tightened finish.
• 2.55m² and 6m² variants currently available.
• Manufacturer provides dedicated fitting instructions.

Trade-off: it costs more per square metre than some generic kits, and—as with other seasonal films—you normally lose easy access to open the window until the film is removed.

Check current tesa product information.

2. Exitex Secondary Glazing Film — best value and UK availability

Best for: a straightforward budget kit that is stocked by several UK retailers.

Exitex sells glazing film in multiple coverage sizes. The 4.5m² version is particularly easy to find in the UK: CPC currently lists it in stock and states that double-sided fixing tape is supplied, while Homebase and Robert Dyas also carry the same 4.5m² product family.

• 4.5m² version widely listed by UK retailers.
• Double-sided fixing tape supplied on the CPC listing.
• Designed to create a secondary-glazing effect.
• Suitable for standard windows and doors.
• Larger Exitex glazing-film sizes are also manufactured.

Trade-off: some retailer pages repeat large percentage heat-loss claims without publishing a test method. We have not used those claims in our ranking or savings guidance.

Check current CPC specification and availability.

3. Stormguard Seasonal Double Glazing Film — best for larger areas

Best for: wide windows, patio-door areas or conservatories where a small film sheet would require too many joins.

Stormguard lists its Seasonal Double Glazing Film in 6m² and 12m² sizes. The manufacturer describes it as a transparent seasonal film that creates a secondary-glazing effect and specifically mentions conservatories as a use case. UK retailer Sealco Scotland currently lists the 6m² version.

• 6m² and 12m² manufacturer-listed sizes.
• Transparent seasonal film.
• Designed to create a secondary-glazing effect.
• Large coverage suits conservatories and wide glazed areas.
• Replacement fixing tape is separately listed by Stormguard.

Trade-off: check the exact retailer pack contents before ordering. Stormguard lists replacement fixing tape separately, so do not assume every listing bundles the same accessories.

Check current Stormguard sizes and product information.

How to choose the right window insulation film kit

Measure total frame coverage, not just the glass

The film normally fixes around the window frame rather than directly to the visible glass. Measure the full area the sheet must span and allow spare material for positioning and trimming.

Choose the fewest joins possible

One continuous sheet is easier to seal and usually looks cleaner than several overlapping pieces. A larger pack can therefore be better value on patio doors or wide windows even if the headline pack price is higher.

Check whether fixing tape is included

tesa states that double-sided tape is included. CPC states the same for the Exitex 4.5m² kit. Stormguard sells replacement tape separately, so confirm the retailer’s pack contents before ordering.

Think about whether the window must open

Shrink film normally spans the opening section. If you need frequent winter access for ventilation or escape, a removable magnetic secondary pane may be more practical.

Check the frame finish before sticking tape

Weak paint, old varnish and delicate finishes can lift when adhesive is removed. Test a discreet section first if the surface condition is uncertain.

What window insulation film cannot fix

• It cannot repair rotten or damaged window frames.
• It does not replace proper draught seals around leaking joints.
• It does not remove indoor humidity or cure the cause of condensation.
• It cannot match the durability of rigid secondary glazing.
• It should never cover trickle vents or required ventilation openings.

If the main problem is air leakage, start with How to Draught-Proof Doors and Windows UK. If the issue is cold glass and night-time comfort, compare Best Thermal Curtains UK as another reversible option.