— Solar & heat

Which window film blocks the most heat?

Reflective and spectrally-selective solar films reject the most heat. Here's how to compare films without the jargon.

1 Jul 2026 · 3 min read

If maximum heat rejection is the goal, the top performers are reflective (metallised) solar films and high-end spectrally-selective ceramic films. Our best films reject up to 79% of total solar energy.

The number that matters

Look for 'Total Solar Energy Rejected' (TSER) — the single figure that captures how much of the sun's heat the film stops. A higher TSER means a cooler room.

Reflective vs spectrally-selective

Reflective films reject the most heat and add a mirrored look (great where you also want privacy). Spectrally-selective ceramic films reject a lot of heat while staying much clearer, so they're ideal where you want to keep the glass looking natural.

Matching film to room

The 'most heat blocked' isn't always the right answer — a mirrored film on a north-facing window is overkill. We recommend the strongest film that suits each window's orientation and the look you want.

Thinking about window film? We offer a free site survey anywhere in Scotland, with most quotes returned within 24 hours.

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