The main benefit of floor insulation is improved thermal comfort, helping to keep your home warmer and more comfortable. It can also reduce energy bills. Insulating a suspended timber floor could save between £45 and £175 per year, while insulating a solid floor could save £30 to £100 per year. Actual savings will depend on your property type (such as a mid-terrace or semi-detached home) and the fuel used for heating, such as mains gas or oil.

Floor insulation improves thermal comfort by stopping draughts and reducing heat loss through the floor. If you want to know more about draught-proofing a floor by sealing the gaps between the floorboards and along the skirting – that information is found here.

Floor insulation is a significant undertaking. It should only be tackled by a professional builder or a very experienced and competent DIY-er.

What kind of floor do you have?

Almost all UK homes will have one of two types of floor. A suspended timber floor (boards laid over wooden joists), or a solid concrete floor.

These are insulated in different ways.

But in each case, if you are the homeowner, it’s your responsibility to adhere to best practice guidelines and comply with Building Regulations.

Adding extra insulation to your existing floor may include making sure:

• The rooms on your ground floor still meet the minimum room heights.
• You achieve minimum U-values (the standard measure of thermal performance).
• You take steps to minimise the risk of fire.
• There is sufficient sub-floor ventilation (an upgrade to the property’s ventilation system may also be required).

It’s a good idea to get advice from a Building Control Officer at your local council before carrying out the work.

Insulating a timber floor

Before you install additional insulation under your floor, make sure any damage from damp, rot or infestation is repaired. You also need to ensure the new insulation doesn’t block any ventilation openings like air bricks.

Rigid insulation board (pictured below) or rolls of mineral fibre (like the stuff used to insulate lofts) can be fitted between the flooring joists. If your floor is above an unheated cellar or basement, you’ll need to fit the insulation snugly between the joists and secure in place with netting if required. Plasterboard should then be fixed to the ceiling of the basement to provide fire resistance.

For older, traditional properties, vapour open insulation materials such as sheep’s wool and wood fibre boards are recommended.

If you have a suspended floor with a small cavity below that’s hard to access, you’ll probably have to take up the floorboards to fit the insulation. However, there are companies like Q-Bot that insulate floors from below. They use a remote-control vehicle – a floor-insulating robot – that surveys the underside of the floorboards, before spraying on insulation.

When insulating a suspended timber floor, a vapour permeable airtightness layer should also be installed. This will reduce heat lost through infiltration but also through the floor fabric.

Insulating a concrete floor

Insulation can be added over an existing concrete slab to make a room warmer and more comfortable.

This is normally in the form of high-performance insulation panels or boards that provide the best thermal performance at any given thickness.

Keeping the thickness of your insulation to a minimum will reduce the likelihood of having to make alterations to door openings, stairs and other fixtures as a result of the increase in floor height.

We recommend laying a damp-proof membrane underneath the insulation (which should overlap any damp-proof course in the external walls) and an airtightness layer and a vapour control layer should be installed on the warm side of the insulation.

In almost all cases this is a job for a professional builder.

If an old concrete floor is being replaced, you will likely be required by Building Regulations to upgrade the insulation at the same time.