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 £235 a year in a typical semi, plus less noise, condensation and draughts.

Estimate your numbers: try the free savings calculator or browse all upgrade guides.