Suspended timber floors: £1,000–£2,600 for a typical home (£25–£50/m² professionally fitted). Solid floors cost more and rarely stack up outside renovation. Here’s the honest maths and the funded routes.
Mineral wool or wood-fibre between joists, netted and breathable: £25–£50/m² installed — £1,000–£1,600 for a 40m² ground floor with decent crawl access, up to £2,600 where boards must lift. DIY-able for confident hands (£300–£600 materials) if airflow to sub-floor vents is preserved.
Insulating a solid floor means raising the floor (PIR + new screed/boarding, £70–£110/m²) with knock-on door and threshold work. Worth it during renovation or extension; rarely as a standalone job. Park homes: bespoke underfloor systems are common ECO4 work — ask on survey.
Uninsulated floors leak ~10–15% of heat: expect £60–£110/year savings plus the comfort jump of warm boards and killed draughts. Underfloor insulation is an eligible measure in ECO4 and WH:LG whole-home packages — could be fully funded for some eligible households; eligibility does not guarantee installation or zero contribution.
Good crawl space (≥600mm) = netting from below at the bottom of the range. No access = boards up, furniture out, top of the range. A borescope check through an air-brick tells an installer which job you are in minutes — check your home and we’ll match one vetted local installer.
AC-coupled (battery has its own inverter) is the retrofit default: no rewiring of your array, works with any brand or age of system, £3,500–£6,000 installed for 5–10kWh usable. DC-coupled only makes sense if your inverter is due replacement anyway — a hybrid inverter + battery swap can be cheaper combined.
Feed-in Tariff payments are unaffected by adding storage — generation payments continue and deemed export isn’t metered down. On SEG, a battery lets you shift export into peak-price windows instead.
Match usable capacity to your evening consumption and summer surplus — the sizing guide has the tables. Most 4kWp homes land at 5–8kWh usable.
Suspended timber floors: £25–£50/m² professionally installed — typically £1,000–£2,600 per home. Solid floors £70–£110/m² and only sensible during renovation.
Yes for suspended floors: £60–£110/year savings, major comfort gain, and draught elimination — payback 8–15 years privately, immediate when grant-funded.
Suspended floors with crawl access are a realistic DIY job (£300–£600 materials) — keep sub-floor vents clear and use breathable netting.
Yes — it's an eligible fabric measure within whole-house ECO4 and WH:LG packages, survey permitting.
Facts checked 21 August 2026. We link to official sources and show when facts were last verified. If a scheme changes, we update the page.
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