Free tool · Passivhaus & retrofit

Warmer home, smaller bills.

Estimate your home's heat demand, energy bills and carbon today — then test measures against Passivhaus and EnerPHit targets with costs, savings and payback for each one.

Your home

Property name or address (optional)

Floor area (m²)Storeys

Property typeAge / constructionMain glazing faces

South-facing living space picks up free winter solar gain — worth up to 8% of heat demand.

LocationCurrent heatingGlazing area · 18% of floor area (22 m²)

Measures & cost benefit

Tick measures to build a package. Each row shows what that single measure would do on its own — ordered by fastest payback.

Solar PV array (approx. 4 kWp)£7,200 capital

Roughly 3,400 kWh/yr in Scotland; value depends on how much you use on site.

£591/yr savedPayback 12.2 yrs−518 kgCO₂e/yr£7,575 net over 25 yrs

Cavity wall insulation£4,046 capital

Only for un-filled cavities. Not available on solid-wall stock.

£197/yr savedPayback 20.5 yrs−556 kgCO₂e/yr£3,834 net over 40 yrs

Loft insulation top-up to 400mm£2,050 capital

Cheapest win in almost every pitched-roof home. Quick, no disruption.

£98/yr savedPayback 20.9 yrs−278 kgCO₂e/yr£1,870 net over 40 yrs

Draughtproofing & airtightness works£4,960 capital

Sealing service penetrations, floor perimeters, letterplates and lofts hatches.

£123/yr savedPayback 40.3 yrs−348 kgCO₂e/yr£-2,500 net over 20 yrs

Suspended / solid floor insulation£3,900 capital

Comfort gain is bigger than the numbers suggest — cold feet disappear.

£74/yr savedPayback 52.7 yrs−209 kgCO₂e/yr£-940 net over 40 yrs

External wall insulation (EWI)£25,740 capital

Best thermal result and no lost floor area, but planning-sensitive on frontages.

£320/yr savedPayback 80.4 yrs−903 kgCO₂e/yr£-12,940 net over 40 yrs

MVHR (heat recovery ventilation)£14,100 capital

Pairs with airtightness — recovers 85–90% of heat and fixes indoor air quality.

£148/yr savedPayback 95.3 yrs−417 kgCO₂e/yr£-10,400 net over 25 yrs

Triple glazing / high-performance windows£17,160 capital

Big comfort and acoustic gain. Specify warm-edge spacers and insulated reveals.

£160/yr savedPayback 107.3 yrs−452 kgCO₂e/yr£-11,560 net over 35 yrs

Air source heat pump (replace boiler)£12,500 capital

Cuts carbon hard. Best installed after fabric works so the unit can be smaller.

£-16/yr savedPayback n/a−2570 kgCO₂e/yr£-12,820 net over 20 yrs

Thermal performance

113

kWh/m²/yr space heat

136

today

Significant heat loss remaining

Passivhaus15 kWh/m²/yr · 98 over

EnerPHit (retrofit)25 kWh/m²/yr · 88 over

Send me the results

See your savings breakdown

Enter your email to reveal bill savings, carbon reduction, payback and 25-year net benefit.

We'll email a copy to the Cole & Partners studio so we can follow up if helpful.

Indicative only — this is a feasibility estimate, not a PHPP model, SAP calculation or EPC. Sequence matters: fabric and airtightness first, then ventilation, then heating plant sized to the improved demand. Always confirm with us or a qualified retrofit designer before proceeding.

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