Working file M1.5
Suspended floor insulation cost (UK 2026)
Suspended floor insulation cost: published installed cost range with the source against each end, plus how it sits in the PAS 2035 fabric-first sequence.
Cost in 2026
Suspended floor insulation cost (UK 2026). The published installed range in 2026 is £38 to £75 per m² installed (Passivhaus Trust v1.3 Jan 2026 benchmark), or £2,500 to £4,500 on a 65 m² ground floor. Both ends of that range are stated rather than collapsed to a midpoint, because the spread reflects real differences in scope, access and grant eligibility rather than installer mark-up.
What drives the spread
- Material: sheep's wool, PIR, woodfibre.
- Access: under-floor crawl space vs lift and re-lay floorboards.
- Airtightness tape and ventilation review are often costed separately.
- PIR yields the lowest U-value per millimetre; sheep's wool is the breathable option for traditional construction.
Where it sits in the PAS 2035 sequence
Pairs with loft and walls under fabric-first sequencing.
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 M1.5]
By Oliver Wakefield-Smith, Founder, Digital Signet. Corrections to oliver at digitalsignet dot com.