Secondary Glazing vs Window Film, Thermal Curtains and Shutters: What Actually Works?

If your windows are cold, draughty or noisy, secondary glazing is not the only option. Window film, thermal curtains and internal shutters are all cheaper, and for some homes one of them may be enough. This guide compares them honestly, so you can decide where your money goes furthest.

The Quick Comparison

Option	Heat loss	Draughts	Noise	Daytime use	Typical cost
Insulating window film	Small improvement	None	None	Yes	Lowest
Thermal curtains	Good when closed	Some	Small	Only when closed	Low
Internal shutters	Good when closed	Some	Small to moderate	Only when closed	Medium
Secondary glazing	Large	Large	Large	Yes, all day	Medium to high

Window Film

Insulating window films are thin, clear low-emissivity coatings applied to the glass. They reflect some heat back into the room and can lower the heat loss through a single pane a little.

• Good for: Rented homes, very tight budgets, and reducing glare or solar heat in summer.
• Not good for: Draughts, because film does nothing for the gaps around the frame, and noise, because a film adds almost no mass to the glass.
• Watch out for: Historic glass. Applying film to old crown or cylinder glass can be risky and may not be acceptable on a listed building.

Thermal Curtains

Heavy lined curtains are one of the oldest and most effective cheap fixes. Research for Historic England on traditional sash windows found that heavy curtains, when closed, cut heat loss through the window by around 40%.

• Good for: Evenings and nights, and as an extra layer with any other measure.
• Not good for: Daytime, because the benefit disappears when the curtains are open. They do little for traffic noise.
• Tip: Curtains work best when they fall to the floor or sill and close tightly at the top, so cold air does not spill out from behind them.

Internal Shutters

Many Georgian and Victorian London homes still have original folding shutters. The same Historic England research found closed shutters cut heat loss by around half.

• Good for: Homes with working original shutters, and night-time heat and security.
• Not good for: Daytime warmth, and serious noise reduction. Timber shutters help a little with noise, but gaps around the panels let sound through.
• Tip: Secondary glazing can usually be designed to fit between the window and the shutters, so you keep using them.

Secondary Glazing

The same research found secondary glazing cut heat loss by around 60%, and unlike curtains and shutters, it works 24 hours a day while still letting in light. It is also the only option here that seals draughts and makes a large difference to noise.

• Good for: Busy roads, railways and flight paths, very draughty sash windows, and listed buildings where replacement is not allowed.
• Not good for: The very tightest budgets, though magnetic DIY secondary glazing is a cheaper starting point.

For the numbers in pounds, read how much can secondary glazing save on energy bills?

Combining Options

These measures work well together. Secondary glazing plus closed shutters or heavy curtains at night gives the best overall result of all. Draught-proofing the original sashes before fitting secondary glazing also helps. See our sash window draughts guide.

Which Should You Choose?

• Mainly cold at night, quiet street, tight budget: Thermal curtains or restored shutters.
• Renting and cannot make changes: Window film and curtains, or removable magnetic panels.
• Noise is the problem: Secondary glazing. Nothing else on this list makes a meaningful difference. See our noise reduction secondary glazing page.
• Cold all day and draughty: Secondary glazing, ideally with curtains or shutters at night.

For prices, see our secondary glazing cost guide, or book a free survey.

Frequently Asked Questions

Is window film as good as secondary glazing?

No. Window film can slightly reduce heat loss through the glass, but it does nothing for draughts or noise.

Are thermal curtains better than secondary glazing?

Heavy curtains are very effective at night but only work when closed. Secondary glazing works all day and also tackles draughts and noise.

Can I keep my shutters with secondary glazing?

Usually yes. Units can be designed to sit between the window and the shutters so the shutters still fold in and out.