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Should you Insulate Under Floorboards?

Fitting floor insulation is a great way to keep the ground floor of your home warm. Here, we look at how to install it and how you can get it for free.

What is underfloor insulation?

Floor insulation is used to insulate floorboards on the ground level of your home and can reduce heat loss due to draughts getting through gaps and skirting boards. Whether it’s to lay on top of a suspended wooden floor or a concrete floor, it could save you money on your heating bills as well as help make your home a warm and cosy place to be.

What is the best way to insulate under floorboards?

Choosing the best way to insulate your flooring depends on the type of floor you have. If you reside in an older property that has a basement or cellar, then you may have a suspended timber floor, with wooden joists visible on the underside of the floorboards. Another clue that you have this type of flooring is ventilation bricks on the outside of your house beneath floor level.

You can insulate the floorboards by lifting them up and laying mineral wool which will need to be supported by netting. To provide fire resistance to the insulation, plasterboard should be fitted to the ceiling of the basement.

Insulation can also be laid over concrete flooring, with high performance insulation panels or boards being the best materials to use due to their high level of thermal performance and minimal thickness.

To ensure that the panels stay dry, it’s a good idea to lay damp-proof membrane underneath the insulation, while ensuring that you don’t overlap any existing damp proof course in the external walls. The panels should come attached to a layer of moisture-resistant chip board. If it doesn’t, it may be wise to lay this on top separately.

Can I install under floor insulation myself?

While laying mineral wool between joists is commonly undertaken by most have-a-go DIYers, the complexity involved in installing it on top of concrete flooring is best left to the experts.

Among the additional considerations are whether to place the damp proof membrane above or below the concrete depending on the manufacturer and ensuring that any timber to be used in the flooring isn’t at risk of warping. Calling in the professionals will ensure that everything is taken into consideration.

What are the benefits of installing floor insulation?

Monthly cost savings vary depending on the type of property and ranges from £30 a year for a mid-terrace house and £75 for a detached house.

While your bills may not be significantly reduced with underfloor insulation alone, it can make a difference when installed alongside other energy-saving solutions. These home improvements can include loft insulation and cavity wall insualtion and an alternative heating system such as an air source heat pump or ground source heat pump.

The reduction in CO2 emissions due to underfloor insulation varies from 310kg a year in a detached house to 120kg in a mid-terrace.

How much does under floor insulation cost?

A typical installation could cost between £520 and £1,300 depending on the circumstances and property type.

Are there any grants for floor insulation?

There are a number of grants to help fund a floor insulation. The main ones are the Energy Company Obligation (ECO) grant, and the Green Homes Grant voucher scheme.

What are ECO Grants?

The Government’s Energy Company Obligation (ECO) is a government-backed energy efficiency scheme that obligates the UK’s big energy companies to help customers on certain benefits pay for energy saving home improvements. As well as providing funding for a free boiler, it also covers a long list of energy saving measures, including floor insulation.


What is the Green Homes Grant Voucher Scheme?

The Green Homes Grant voucher scheme (GHGVS) provides vouchers for energy efficiency measures, including funding for floor insualtion. It’s split between those on low incomes and certain benefits, who can apply for vouchers that cover the total cost up to £10,000, and a general scheme that is open to all and provides grants that cover two-thirds of the cost, up to £5,000.

This means, in the general scheme, underfloor insulation costing £900 would cost you £300, with £600 covered by the vouchers.