Double Glazing Savings Calculator

Double glazing replaces single-pane windows with sealed units containing two panes of glass separated by an insulating gap (typically 16mm of argon gas). This significantly reduces heat loss — a single-glazed window has a U-value of around 5.0 W/m2K, while standard double glazing achieves 1.4 W/m2K, and triple glazing reaches 0.8 W/m2K.

The cost of double glazing depends on window count, size, frame material (uPVC is cheapest at £300-£600 per window, timber £400-£800, aluminium £500-£900) and whether you need new frames or just replacement glass units. A typical 3-bed semi with 10 windows costs £4,000-£8,000 for full uPVC double glazing.

Energy savings from replacing single glazing with double glazing are estimated at £100-£200 per year by the Energy Saving Trust. The payback period is long (20-40 years on energy savings alone), so double glazing is best justified by combined benefits: energy saving, noise reduction, security improvement and property value increase.

UK double glazing costs 2026. Small-medium home (3-bed semi, 8-10 windows): £4,000-£8,000 for full uPVC replacement. Premium aluminium frames: £6,000-£12,000. Timber-look composite: £8,000-£18,000. Sash window restoration with secondary glazing: £600-£1,500 per window. Per-window pricing: standard casement uPVC £400-£800 each; large bay window £1,200-£2,500. Patio doors: £900-£2,500; bi-fold doors: £2,500-£6,000+. Always get 3+ quotes — pricing varies wildly between national chains and local installers.

U-values — what to look for. Building Regulations Part L (2022): new windows U-value max 1.4 W/m²K. Top-rated A++ windows: 0.8-1.0 W/m²K. Single glazing (Victorian): 5.0-5.8 W/m²K — terrible. Old double glazing (1990s): 2.5-3.0 W/m²K. Modern triple glazing: 0.7-1.0 W/m²K. Lower is better. WER (Window Energy Rating) A++ to G: like fridge labels. Choose A or A+ for best balance of cost and performance.

Savings from new double glazing. Replacing single glazing with A-rated double: saves £200-£500/year on heating (typical UK home). Replacing 1990s double with modern A++: saves £80-£200/year. Payback period: 15-30 years on pure energy savings. Other benefits: noise reduction (35-50% with acoustic glass); condensation reduction; security (laminated glass, multi-point locks); aesthetic. Most homeowners don't 'pay back' purely from energy — but combined with quality of life, security, and house resale value, it's worthwhile.

Listed buildings and conservation areas. Listed (Grade I, II*, II): cannot fit standard uPVC windows. Must apply for listed building consent (free, council-administered, takes 8-12 weeks). Options: timber sash windows with slim-profile double glazing (~£1,500-£3,000 per window); secondary glazing (single-glazed external windows + internal pane — preserved appearance £600-£1,500/window). Conservation areas: planning permission for front-facing windows visible from highway. Article 4 directions sometimes restrict ALL window changes.

FENSA/CERTASS — installer certification. Mandatory for new windows installed in domestic properties since 2002 (Building Regulations compliance). Installers must be: FENSA, CERTASS, or DCLG-approved Competent Person Scheme member. Self-certify Building Regulations compliance. Provides: 10-year insurance-backed guarantee. Without FENSA/CERTASS: Building Regulations breach — affects future house sale, mortgage applications. Cost included in installation price. Check installer's certification before signing contract.