Floor insulation explained

See guide sections

In this guide

Save money on your energy bills

Enter your postcode below to get started

Please enter valid UK postcode.

Start comparing

We value your privacy; we only use your postcode to compare offers in your area.

Do I need floor insulation?

Current building regulations require all new builds to reach certain standards when it comes to energy efficiency. The level of insulation can be measured with something called the U-value; this represents the amount of heat that can escape through each part of your house.

UK building regulations ask for a ground floor U-value of 0.25 W/m^2. This regulation has changed over time, so older builds are likely to have little to no ground floor insulation. Older homes are also more likely to have draughts, making the house less efficient. These draughts can be reduced through insulating and sealing floors.

Floors only need to be insulated if they are above an unheated space, this includes ground floor rooms or spaces above unheated garages or basements.

The fuel savings from insulating your floors are not as great as wall or roof insulation so shouldn’t necessarily be your first priority when insulating your house, however, in many cases DIY floor insulation is possible and far cheaper to install.

Cost and Energy Savings

Even though heat rises, some heat is always going to escape into the ground beneath your house or into any other unheated areas. Insulating your floor will go a long way to keeping heat trapped inside the house, meaning less fuel is needed to keep your house cosy and will reduce your yearly fuel bill

Yearly energy savings will depend on the type of building you live in and the amount of ground floor space you have and your current levels of insulation. The following table shows the average yearly fuel savings for different property types with a fully insulated ground floor.

Installation costs for ground floor insulation will vary but typically costs somewhere between £520 and £1,300. This cost can be offset by installing the insulation yourself or by claiming under the UK’s Green Home Grant scheme.

How to insulate your floor

For some smaller jobs, it is possible to insulate your floor yourself, for more complicated jobs it is important to get the advice of an installer registered with the National Insulation Association (NIA). Ultimately, it depends on the type of floor you have.

• Solid Concrete Ground Floor

These are generally found in newer builds and can be insulated by layering a damp-proof membrane, 180mm of rigid insulation board and topping with a layer of chipboard or floorboards. This can raise the height of your floorboards, meaning you might need to replace plug sockets and skirting boards, so keep this in mind when budgeting.

If you are having your floor replaced, then contractors must also include proper levels of insulation in the build to comply with building regulations.

• Suspended Timber Floors

These tend to be more common in older builds which also include ventilation bricks under floor level. These can be insulated by cutting oversize layers of 150mm thick mineral wool insulation and wedging them between the floor joists. A similar level of insulation can be achieved with 90mm of rigid foam insulation.

Make sure that no ventilation bricks are covered, and a 25mm gap is left between the insulation and the floorboards as this can cause condensation and damp.

Insulation can be improved by sealing your floorboards and preventing draughts. This can be done yourself using easily applied sealant available at most DIY shops.

Some companies are now offering robot applied spray foam insulation for a suspended timber floor. This can provide better insulation but will be more expensive.

• Basement space

Insulating floors above an unheated basement space can be insulated in the same way as suspended timber flooring with insulation being held in place using netting. It recommended that a layer of plasterboard is also installed to provide some fire resistance.

While most of these jobs can be done yourself, if you feel uncomfortable lifting floorboards or working around pipes, get an NIA registered professional to install it for you.