Definition: Double glazing uses two panes of glass with an insulating gas gap, roughly halving window heat loss versus single glazing. A whole-house replacement typically costs £3,500-£8,500.
Ratings
Look for A-rated or better windows and a whole-window U-value of 1.4 W/m²K or lower. uPVC is cheapest; aluminium and timber cost more but last longer or suit period homes.
Savings
Upgrading from single glazing saves about £104 a year in a typical semi at the October 2026 price cap (Energy Saving Trust figure), plus less noise, condensation and draughts.
Estimate your numbers: try the free savings calculator or browse all upgrade guides.
See what double glazing cost in your town
Prices for 160 towns, with the grant position for your nation.