A big south- or west-facing glazed wall is glorious in spring and an oven in July. Solar control glass fixes the overheating without turning the glass into sunglasses.
g-value: the number to watch
The g-value (solar factor) is the fraction of the sun's heat that passes through the glass. Lower g means less heat gain. Solar control coatings drop the g-value while keeping the glass reasonably clear, so you lose the heat problem but keep the view and the light.
- g-value
- lower = less solar heat
- Light transmission
- kept high on good coatings
- Best for
- south / west, large glazing
- Pairs with
- low-e for winter warmth
- Look
- subtle, not mirrored
Balancing summer and winter
Good glass does two jobs: rejects summer sun (low g-value) and retains winter warmth (low-e coating, good Uw). Modern coatings achieve both, which is why solar control rarely means a cold, dark room — see U-values explained.
Where it pays off most
It is most worthwhile on large glazed elevations — a wall of aluminium bifold doors or a big slider facing the afternoon sun. On modest north-facing windows it is usually unnecessary.
Specifying without over-tinting
Ask to see a sample against the light so the tint meets your taste before you commit. A supplier used to large glazed openings — such as premium glazing specialists — can recommend a coating that controls heat without darkening the room.