Flagship guide · 11 min read
The Complete Guide to Glass Specification
The frame gets most of the attention, but the glass does most of the work. This is our full guide to choosing it properly.
Solar Control Glass Explained
Large glazed openings on sunny elevations can overheat rooms even in a cool climate. Solar control glass is the usual solution.
3 min read
As glazed areas have grown — bifold and sliding doors spanning several metres are now common on garden elevations — overheating has become a more frequent complaint than heat loss on those same rooms. Solar control glass is the direct answer, reducing the amount of solar energy that passes through the glass as heat while keeping the room bright.
This guide explains how it works, where it is worth specifying, and what to expect from it visually and in terms of cost.
How solar control glass works
A solar control coating is a thin metallic or metal oxide layer applied to one surface of the glass, usually surface 2 (the outward-facing side of the cavity). It reflects a proportion of the sun's infrared energy back outside before it can be absorbed and re-radiated into the room as heat, while allowing most visible light through so the room stays bright.
The result is measured as a g-value: the fraction of total solar energy that reaches the inside. Standard clear glass has a g-value around 0.6–0.7. A good solar control unit can bring that down to around 0.3–0.4, roughly halving the solar heat gain, while keeping light transmittance close to 70%.
Where it earns its place
- South and west-facing bifold or sliding doors onto a garden or terrace
- Rooflights and roof lanterns, which receive the most direct solar exposure of any glazing
- Large picture windows framing a view on an unshaded elevation
- Conservatories and garden rooms with substantial glazed roof or wall area
- Upper-floor rooms under a warm roof with limited cross-ventilation
What it looks like
Modern solar control coatings are close to neutral, with a very slight blue-grey or green cast visible mainly from outside at certain angles, or against a bright sky. From inside, looking out, the effect on colour is minimal. This is quite different from tinted or reflective glass, both of which have a visibly stronger colour or mirror effect and are chosen partly for their appearance as well as their solar performance.
Combining with other specifications
| Combination | Effect |
|---|---|
| Solar control + low-iron | Solar reduction with maximum clarity and colour neutrality — popular for large view-facing doors |
| Solar control + acoustic laminate | Overheating and noise addressed together, useful on a busy south-facing road elevation |
| Solar control + triple glazing | Combines strong thermal performance with reduced summer gain — worth it on exposed, sun-facing self-builds |
What it costs
Solar control is one of the more affordable glass upgrades, typically adding a modest per-window premium over standard low-e glass rather than materially changing the overall project figure. On a large sliding or bifold door, where the glazed area is greatest and the overheating risk highest, it is usually the single best-value upgrade available.
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