Reduce heat loss through your windows by up to 75% and significantly lower your energy bills. Our thermal secondary glazing creates an insulating barrier that transforms the comfort and efficiency of your home, ideal for Victorian, Georgian, and Edwardian properties.
Heat Loss Reduction
Annual Savings
U-Value Achievable
EPC Points Potential
Single-glazed windows are the biggest source of heat loss in most homes, with U-values typically around 5.0 W/m²K. By adding secondary glazing, you create an insulating air gap that dramatically reduces heat transfer. The trapped air between the two layers of glass acts as an effective thermal barrier, similar to the principle behind double glazing.
Unlike double glazing, which replaces your existing windows, secondary glazing works with them. This means you can achieve excellent thermal performance while retaining original windows in Victorian, Georgian, and Edwardian properties, conservation areas, and listed buildings.
Lower U-values mean better insulation. Secondary glazing with low-E glass achieves thermal performance approaching that of modern double glazing.
A microscopically thin metallic coating reflects heat back into the room while allowing light to pass through.
Heat-treated for strength, toughened glass is 4-5 times stronger than standard float glass.
The air gap between your existing window and the secondary glazing is crucial for thermal performance. For optimal insulation, we recommend a minimum gap of 20mm, with 100mm or more providing the best results. Larger gaps also help prevent condensation forming between the two layers of glass.
The air gap works because still air is an excellent insulator. Heat must pass through both layers of glass and the trapped air between them, dramatically slowing the rate of heat transfer compared to a single pane. This is particularly effective for sash windows which typically have deep reveals.
Typical savings of £300-500 per year on heating costs for an average London home.
Lower energy consumption means reduced CO2 emissions from your home.
No more cold areas near windows, improving comfort throughout your home.
Secondary glazing can improve your Energy Performance Certificate by 10-15 points.
Condensation on windows occurs when warm, moist air meets a cold surface. By keeping the inner glass surface warmer, secondary glazing significantly reduces condensation, preventing damage to window frames and reducing the risk of mould growth.
For properties with severe condensation issues, we can incorporate small ventilation holes in the secondary glazing to allow moisture to escape while maintaining thermal performance. Combined with acoustic glass, you can achieve both thermal and noise reduction benefits.
Secondary glazing can reduce heat loss through windows by up to 75%, typically saving 15-30% on heating bills. U-values improve from approximately 5.0 to 1.8-2.8 W/m²K.
Yes, secondary glazing significantly reduces condensation by keeping the inner glass surface warmer. This prevents moisture buildup and associated dampness problems.