Insulation for lofts, walls and floors

Loft insulation between and over the ceiling joists is the simplest measure where the loft is accessible and unconverted. If you want to use the loft for storage, boards should sit on raised legs so the insulation is not squashed. A converted loft or room in the roof needs insulation in the sloping ceilings and walls instead.

Many houses built from the 1920s onwards have cavity walls: two leaves of masonry with a gap between them. Cavity wall insulation is blown into the gap through small holes drilled in the outer wall. Whether it suits your house depends on the cavity width and condition, the exposure of the walls to driving rain and the state of the brickwork and pointing.

Older homes usually have solid walls, which can be insulated internally, with boards fixed to the inside and a loss of room space, or externally, with insulation and a new render or cladding outside. Suspended timber ground floors can be insulated from below, from a cellar or crawl space, or by lifting the floorboards. The basement ceiling insulation common on the Continent is the same idea, and in British homes it mostly applies to houses with a cellar under a suspended floor.

Insulation changes where a building is warm and where it is cold, and moisture follows. Loft insulation pushed into the eaves blocks the ventilation that keeps roof timbers dry. Cavity fill in a wall exposed to driving rain, or with defective pointing, can carry water across to the inner leaf. Internal wall insulation without proper vapour control, or with gaps around joists and window reveals, can create cold spots where condensation and mould form.

As a home becomes more airtight, it needs controlled ventilation: working extractor fans in kitchens and bathrooms, trickle vents and, in some whole-house projects, mechanical ventilation. A careful installer surveys first and tells you if the walls are unsuitable or need repairs before any insulation goes in.

Be cautious about spray foam applied to the underside of roof slopes. It can hide the condition of the timbers, and some surveyors and mortgage lenders are reluctant to accept it, which can cause trouble when you sell or remortgage. Home Energy Scotland does not fund spray foam insulation at all.

Cavity wall insulation is notifiable building work in England. A building notice has to be given to Building Control, which an installer registered with a competent person scheme usually does for you; always check that it has been done. The Building Regulations also require the material to suit the wall construction.

When a quarter or more of an external wall, roof or floor is renovated, the Building Regulations normally require that element to be insulated to the current standard, unless that is not technically or functionally feasible. That catches people out when re-rendering a wall or re-roofing.

Fitting insulation does not normally need planning permission if the outside appearance does not change. External wall insulation changes it: in a conservation area, national park, Area of Outstanding Natural Beauty or the Broads, cladding or rendering the outside of a house needs planning permission, and listed buildings need listed building consent for significant work inside or out. Wales, Scotland and Northern Ireland have their own rules.

Cavity wall insulation fitted by a registered installer can come with an independent 25-year guarantee from the Cavity Insulation Guarantee Agency (CIGA). Ask for it in writing, and keep it with the house deeds, because buyers' surveyors ask about cavity fill.

For grant-funded retrofits in Great Britain, TrustMark oversees technical and consumer protection standards. The government has issued a statement about potential problems with insulation installed under ECO and the Great British Insulation Scheme, which is a reminder to insist on a survey and to know who is responsible for putting mistakes right.

• the areas to be insulated and the material, thickness and product used
• a survey of the walls or roof, including damp, pointing, rain exposure and ventilation
• how ventilation will be kept or improved, for example at the eaves or in wet rooms
• for internal wall insulation, how sockets, radiators, skirting and window reveals are dealt with
• for external wall insulation, the render or cladding finish, scaffolding and details at windows, eaves and pipes
• Building Regulations notification where needed, and any planning permission
• the guarantee and who provides it

Installing insulation in a home is zero-rated for VAT until 31 March 2027, after which the reduced rate of 5% applies. In England, low-income households in privately owned homes with an EPC of D to G can receive wall, loft and underfloor insulation through their council's Warm Homes: Local Grant; the income limit is usually £36,000 a year. ECO4, funded by energy suppliers for low-income and vulnerable households, runs until 31 December 2026.

In Scotland, the Home Energy Scotland Grant and Loan pays up to £7,500 towards solid wall insulation and up to £1,500 towards loft, cavity and underfloor insulation, with an extra £1,500 for rural and island homes; you need a valid EPC that recommends the measure. In Wales, the Nest scheme offers free advice and, for eligible households, free insulation.

Source: gov.uk · gov.uk · gov.uk · ofgem.gov.uk

Tell us what you would like insulated, the type of house and roughly when it was built, then confirm your phone number by text-message code and your email address by link. We offer the request, stripped of your name and contact details, to insulation installers in your area. Only one can buy it; the installer pays Offrano for it and the request is removed. For you, the service is free.

Before that installer sees who you are, we email you its name, address and phone number. You can withdraw your consent via the link in every email. We cannot guarantee that an installer takes the request; if none does within 21 days, it is withdrawn, and you are free to get quotes elsewhere. Offrano checks that the buyer is a registered business, not the quality of its work, so ask about TrustMark registration and CIGA guarantees yourself.