Contact

Guide · Home energy

Loft insulation: what to check and what to do next

An accessible loft with little or patchy insulation is often one of the simpler places to reduce heat loss. Check what is already there, deal with damp first, and keep ventilation, wiring and water tanks in mind.

By energy.org.uk editorial team · Reviewed by energy.org.uk editorial team · Published and updated 2 October 2026

Who this is useful for

  • Homes with an accessible pitched-roof loft and thin, patchy or squashed insulation.
  • Homes where insulation is missing around the hatch, at the eaves or under boarded areas.

Energy Saving Trust says current building regulations recommend at least 270 mm of mineral wool. Rooms in the roof, flat roofs, lofts with damp, and lofts with existing spray foam need specialist advice rather than a simple top-up.

What to check first

  • Depth and coverage. Measure in several places, including near the eaves and under any boards.
  • Damp. Look for leaks, wet or stained timber, mould or condensation. Fix these before adding insulation.
  • Ventilation. Vents at the eaves, in the tiles or at the ridge must stay clear. Insulation should not be pushed into the eaves so that it blocks airflow.
  • Wiring and lights. Energy Saving Trust warns that covering electrical cables with insulation is a fire risk, so lift cables on top. Recessed downlights in the ceiling below may need a support that keeps insulation away; some fire-rated fittings are designed to be covered. Check the fitting, and ask an electrician if you are unsure.
  • Water tanks and pipes. Do not put insulation under a cold-water tank: warmth from below helps stop it freezing. Insulate the sides and top of the tank, and the pipes in the loft, instead.
  • The hatch. Insulate and draught-strip the loft hatch.
  • Storage. If you board the loft, raise the boards above the insulation so it is not squashed, and leave a small gap for ventilation.
  • Unfamiliar materials. If you find loose-fill material you do not recognise, do not disturb it until you have advice.

Ventilation and moisture

Insulation keeps heat in the rooms below, so the loft becomes colder. Energy Saving Trust notes that this makes condensation more likely and can worsen existing damp.

Keep the loft’s ventilation clear. Seal gaps where warm, moist air can rise into the loft, such as around the hatch, pipes and cables. Use extractor fans in kitchens and bathrooms. Never block vents to make the loft feel warmer.

Practical next steps

  1. Measure the depth, take photographs and note any damp, wiring or tanks.
  2. Fix leaks and damp first.
  3. For an easy-to-reach loft with regular joists, topping up yourself may be possible. Wear protective clothing and follow the product instructions. Otherwise, use an installer.
  4. Get written quotes covering the material and depth, the hatch, tanks and pipes, eaves ventilation, any boarding, and removal of old material.
  5. Check whether you qualify for help (see below).

Grants and support

Help depends on where you live, your income and your home. Check the official service for your nation, and never pay anyone to “unlock” a government grant.

  • England: the Warm Homes: Local Grant is run through councils for lower-income households in homes with an EPC rating of D to G. Availability varies by council.
  • Great Britain: the Energy Company Obligation (ECO4) runs until 31 December 2026. Whether a supplier will take a new application depends on its delivery plans. The Great British Insulation Scheme closed on 31 March 2026.
  • Scotland: Warmer Homes Scotland, through Home Energy Scotland.
  • Wales: Nest, through the Welsh Government.
  • Northern Ireland: the Affordable Warmth Scheme, through the Housing Executive.

See current help and grants for more detail.

Important limitations

  • How much you save depends on how much insulation is there now, your home and how you heat it. We do not give a single saving figure.
  • Loft insulation does not deal with heat lost through walls, floors, windows or draughts.
  • Rooms in the roof and flat roofs need a different approach.

Related tools and guides

Sources

Official sources checked 2 October 2026.