Author: Oliver Wakefield-Smith, Founder Digital Signet. Reviewed against DfE Sustainability Strategy (Mar 2025) and Education Estates Strategy (Feb 2026). Verified 22 June 2026.
The worksheet below pre-loads a typical 1945-1976 secondary (7,500 m2, gas heating, South East region). The output panel reads as a governor paper: per-school ceiling, grant offset, net cost, Ofgem Q3 2026 payback, tCO2e abated per year.
ASHP sized to 478 kW from heat-loss coefficient.
Heat-loss coefficient 75 W/m2 multiplied by 7,500 m2 yields a 562.5 kW design heat-loss; multiplied by an 0.85 utilisation factor gives an installed ASHP capacity near 480 kW. At £2,000/kW and a 1.10 regional multiplier that is £1.05m of ASHP CAPEX. Fabric at £240/m2 multiplied by 7,500 m2 and 1.10 adds £1.98m. Solar PV at 80 kWp adds £96,800. LED at £25/m2 adds £206k. BMS adds £77k. Total per-school ceiling lands near £3.4m before any grant offset; with PSDS Phase 4 plus Salix CIF the net falls to the Salix per-project payback gateway.
Use the Print as board paper button to render an A4 portrait version with the Source-of-record banner, the Ceiling Headline, the leaf-vein ladder, the kWh / tCO2e Sankey strip and the BoardPaperFooter colophon. Pasted straight into a trustee pack the page reads as a Salix Annex B-style appendix.