Designing for comfort throughout the year

A glass extension should be a room you can enjoy across the seasons. We consider the glazing, orientation, ventilation, shading and heating together, with your day-to-day use of the space in mind.

Choosing multifunctional glass

We use Saint-Gobain SGG COOL-LITE SKN 183, which combines solar control with thermal insulation while allowing high levels of daylight into the room.

Its coating helps limit incoming solar heat during sunny weather. Its low-emissivity properties help reduce heat loss in colder conditions. This supports comfort while retaining the light and views that make a glass extension appealing. Saint-Gobain product guidance ↗

Glass specification

Saint-Gobain publishes the following reference figures for COOL-LITE SKN 183 II: 75% visible light transmission, a solar factor of 0.40 and a centre-pane U-value of 1.0 W/m²K. A solar factor of 0.40 means approximately 40% of incident solar energy enters through the glazing.

These figures apply to a 6–16–4mm double-glazed unit with 90% argon. Your actual glass build-up, including laminated panes, thicknesses and roof application, needs its own performance confirmation. The centre-pane U-value does not rate the complete extension. Saint-Gobain performance table ↗

Considering the whole room

The direction your extension faces and the balance of roof and vertical glazing influence how much sunlight it receives. We discuss ventilation and heating, together with shading where needed to manage strong sunlight and glare.

Insulation, connection details and moisture control also matter when assessing condensation risk. Thermal calculations and an overheating assessment, where appropriate, help the team evaluate the proposed design.

The glass is an important part of this approach. Comfort comes from matching its performance with the room's layout and environmental design.

Talk to Glasspace about how you plan to use your extension throughout the year. Discuss your project ↗