Author: Oliver Wakefield-Smith, Founder Digital Signet. Reviewed against DfE Sustainability Strategy (Mar 2025) and Education Estates Strategy (Feb 2026). Verified 22 June 2026.
Double glazing at £650 to £850 per m2 of opening (frame and glazing combined, contractor-fitted). Triple glazing at £950 to £1,250. Heritage timber double glazing pre-1944 commonly lands above £1,400 once conservation officer requirements apply.
Double glazing at £650 to £850 per m2 of opening (frame and glazing combined, contractor-fitted). Triple glazing at £950 to £1,250. Heritage timber double glazing pre-1944 commonly lands above £1,400 once conservation officer requirements apply.
Glazing alone rarely clears the Salix payback gateway on average; bundled with fabric and BMS controls it does. The PSDS Phase 4 scoring framework rewards bundled fabric scopes over standalone glazing replacements.
EnerPHit-certified retrofit window U-values target 0.85 W/m2K or below for new openings. Schools targeting EnerPHit commonly install triple glazing with insulated frames; the resulting heat-loss coefficient lift unlocks a smaller ASHP.
Pre-1919 schools with single-glazed sash windows carry the highest £ per m2 but also the steepest kWh saving. Listed-building consent often constrains the glazing specification; allow 12 to 18 months for the planning process.