retrofitcost.co.ukA surveyor's working file. Q3 2026 Ofgem cap applied.
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Working file M0

Retrofit measures by stratum (PAS 2035)

The five PAS 2035 measure strata, costed in 2026: fabric, ventilation, heating, renewables, controls.

  1. Stratum 1FabricEWI, IWI, cavity, loft, floor, glazing£14k to £30k
  2. Stratum 2VentilationMVHR, PIV, dMEV£0.5k to £11k
  3. Stratum 3HeatingASHP, GSHP, hybrid, radiator upsize£9.8k to £18.5k
  4. Stratum 4RenewablesSolar PV, battery storage£8.3k to £14k
  5. Stratum 5ControlsSmart thermostat, zoning, weather comp£0.35k to £0.95k

Sequencing rule

PAS 2035 sequences fabric first because the heating capacity, the ventilation strategy and the renewables sizing all depend on the post-fabric heat-loss calculation. A heat pump sized to the pre-fabric heat-loss is the most common mis-design in the UK installer base.

Strata

Surveyed 22 June 2026. Ofgem Q3 2026 cap applied (gas 7.33p, elec 26.11p, gas standing 29.04p). Next scheduled review 26 September 2026 (Q4 cap publication). [ref M0]
By Oliver Wakefield-Smith, Founder, Digital Signet. Corrections to oliver at digitalsignet dot com.