Underfloor Insulation Grant 2026

What underfloor insulation is

Underfloor insulation adds an insulating layer to the ground floor of your home, so heat does not leak downwards into the void beneath the floorboards or into the ground. In a typical uninsulated house the floor is not the biggest heat loss — the roof and the walls are — but it is the one you feel most directly, because cold air moving through a suspended floor produces draughts at ankle level and cold floorboards underfoot all winter.

It is also the measure people most often overlook. Loft insulation is visible and easy to check; the underside of your floor is not. If your home was built before the 1950s and nobody has touched the floor since, there is a good chance it has no insulation at all.

Suspended timber floors vs solid floors

Which type of floor you have decides what is possible, how much it costs, and whether a grant scheme will fund it.

Suspended timber floors

Common in homes built before about 1950. Floorboards are laid over timber joists, which sit above a ventilated void with bare earth or concrete below. Airbricks in the outside wall keep that void ventilated so the timbers do not rot — which is exactly why the floor is cold: outside air is flowing under your living room by design.

These floors are the straightforward case. Insulation is fitted between the joists from below where there is a cellar or crawl space, or from above by lifting the floorboards. Either way the airbricks stay clear. If you can rock a floorboard, hear a hollow sound when you tap the floor, or see airbricks low down on the outside wall, you probably have a suspended timber floor.

Solid floors

Standard in homes built from roughly the 1950s onwards: a concrete slab, often with screed and a damp-proof membrane. There is no void to fill. Insulating a solid floor means either laying rigid insulation boards and a new floor surface on top — which raises the floor level and means doors, skirtings and thresholds all have to be altered — or digging the floor out and rebuilding it, which is major structural work.

Because of that cost and disruption, solid floor insulation is rarely funded as a stand-alone grant measure. It tends to appear only where a floor is being replaced anyway, or as part of a deep whole-house retrofit. If you have a solid floor, the honest advice is to put your effort into the loft, the walls and draught-proofing first.

What the grants actually fund

Underfloor insulation is a recognised measure under both live schemes, which means the scheme pays for the survey, the materials, the labour and the making-good — not a contribution towards it.

• ECO4: funds underfloor insulation as part of a whole-house package. ECO4 works on the improvement in a property's energy rating, so a single low-impact measure rarely gets approved on its own — floor insulation is usually bundled with loft, wall or heating measures. Runs to 31 December 2026.
• Warm Homes: Local Grant: England only, April 2025 to March 2028, delivered through councils and their appointed installers. Floor insulation counts against the £16,600 energy-performance cap, which is generous enough that it is not the limiting factor here.
• LA Flex: a council declaration route into ECO4 for households with no qualifying benefit. Same measures, different front door.

A retrofit assessment under PAS 2035 decides the package. If your floor is cold but your loft is empty, expect the loft to be done first — it costs less and saves more. That is not a brush-off; it is how the schemes are scored.

Underfloor insulation grants: who qualifies in 2026

Three live routes, and you only need to clear one.

ECO4 — qualifying benefits

Someone in the household must receive one of the qualifying benefits: Universal Credit, Pension Credit (Guarantee or Savings Credit), Income Support, income-based Jobseeker's Allowance, income-related Employment and Support Allowance, Housing Benefit, or Child Benefit within the scheme's income thresholds. Disability benefits such as PIP, DLA and Attendance Allowance do not qualify on their own: the household also needs one of the means-tested benefits above, or an LA Flex route. The property normally needs an EPC rating of D or below. See our full guide to ECO4 eligibility.

Warm Homes: Local Grant — England, no benefit needed

One of three routes must apply: gross household income under £36,000 a year before tax; someone in the home receiving Universal Credit, Pension Credit, Housing Benefit, Income Support, income-based JSA or income-related ESA; or a home in a postcode among the most income-deprived 20% in England. The home must be EPC D to G, and you must be an owner-occupier or a private tenant with the landlord's consent. Privately rented F and G homes need a registered MEES exemption. Social housing is not eligible; park homes are. Councils must make contact within 10 working days of a referral, and not every council joined the programme.

LA Flex — your council's own criteria

Councils publish a statement of intent setting out who they will declare eligible — typically an income ceiling, a health condition made worse by a cold home, or a referral from a health or support service. No benefit claim required. LA Flex sits inside ECO4, so it closes when ECO4 does.

Scotland and Wales

ECO4 applies across Great Britain, so a Scottish or Welsh household on qualifying benefits can be funded through it. The Warm Homes: Local Grant is England only. In Scotland the equivalent is Warmer Homes Scotland, reached through Home Energy Scotland; in Wales it is the Warm Homes Nest scheme.

Nobody is guaranteed a grant. Funding is finite, delivery is postcode by postcode, and the assessment can conclude that your money is better spent elsewhere in the house.

How underfloor insulation is installed

For a suspended timber floor there are two approaches.

From below, where there is a cellar or a crawl space with enough headroom. Insulation — usually mineral wool held in netting, or rigid boards cut between the joists — is fitted up against the underside of the floorboards and supported so it cannot sag away and leave an air gap. Nothing inside the house is disturbed. This is much the tidier job, and it is the one installers hope for.

From above, where there is no access underneath. Floorboards are carefully lifted, insulation is laid between the joists on netting or battens, and the boards go back down. Carpets and furniture have to come up, and a room at a time is normal. Original boards can usually be re-laid, but some splitting is realistic on a Victorian floor.

In both cases the installer should also seal gaps around the perimeter and between boards, which is where much of the draught comes from, and must leave the airbricks completely clear. Typical time on site is one to two days for a standard ground floor, longer if boards are being lifted throughout.

How much does underfloor insulation save?

The saving is modest — typically up to around £100 a year depending on the house. That is modest next to loft or wall insulation, and it is why floor insulation is a supporting measure rather than a headline one.

The comfort gain is out of proportion to the number, though. Stopping cold air moving under the floor removes the draught at foot level that makes a room feel colder than the thermostat says it is, and it stops the floor itself acting as a cold surface. Households often report being able to turn the thermostat down a degree after the floor is done — which is where the real saving comes from.

Paid privately, insulating a suspended floor typically runs into the hundreds rather than the thousands where there is crawl-space access, and considerably more where boards must be lifted. Insulating a solid floor is a different order of cost altogether.

Ventilation, damp and what to watch

The one thing that must not happen is blocked airbricks. The void under a suspended timber floor is ventilated so moisture cannot build up around the joists; cover the airbricks with insulation, debris or a later extension and you invite rot. Any competent installer knows this, but it is worth checking yourself afterwards — walk round the outside of the house and confirm every airbrick is clear.

Two other things to raise at the survey:

• Existing damp or rot. If the joist ends are damp or there is standing water in the void, that gets fixed before anything is insulated. Insulating over a wet floor makes it worse.
• Pipework and cabling. Water pipes in a newly insulated void sit on the cold side of the insulation and should be lagged, or they will be more likely to freeze than before.

Grant-funded work must be done by a TrustMark-registered installer to the PAS 2035 retrofit standard, which puts an assessor and a retrofit coordinator between you and a poor install, and gives you a route to complain if it goes wrong.

How to apply

1. Check all three routes at once. The eligibility checker covers ECO4, LA Flex and the Warm Homes: Local Grant in a single pass. In England you can also apply directly on GOV.UK.
2. Have your evidence ready. Benefit award letters or proof of household income, your EPC, and written landlord consent if you rent.
3. Whole-house assessment. An assessor looks at the entire property, not just the floor, and a retrofit coordinator specifies the package. Ask specifically whether the floor is included, and if not, why.
4. Access survey. The installer checks whether there is a crawl space, what the void looks like, and whether boards need lifting.
5. Install and sign-off. One to two days for most ground floors, then TrustMark lodgement and usually a new EPC.

If your floor is not included in the package, it is worth asking about loft insulation, cavity wall insulation and room-in-roof insulation in the same visit — those are the measures that move an EPC fastest, and getting one approved often brings the others with it.