Windows are one of the biggest sources of heat loss in any home. The thermal performance of a glazing unit is measured by its U-value — the lower the number, the better the insulation. Old single-glazed windows typically have a U-value around 5.8 W/m²K, while modern A-rated double glazing achieves around 1.2 W/m²K.
Upgrading your glazing doesn't just reduce your heating bills — it can improve your EPC rating, reduce condensation, and make your home noticeably more comfortable in winter and summer. The payback period depends on how many windows you upgrade and your current glazing type.
Our calculator factors in your property type, number of windows, current glazing specification, and local energy costs to give you a realistic annual savings estimate.