Floor insulation 3

Floor insulation

  • Insulate and draught proof the floors in your house to help save money
  • Pick the best insulation for your floor
  • Floor insulation costs and savings and how to find a good installer

If you have already installed loft insulation and wall insulation and are keen to save even more on your heating bills, then the next insulation job is your floor.

Floors on the ground floor can feel pretty cold and should be insulated if possible. The floors of upstairs rooms do not usually need to be insulated if the room or space underneath is heated. But if your room is above an unheated space, such as a garage, you could benefit from floor insulation.

And if you want to go even further to make your toes toasty, see how an underfloor heating system can help.

Floor insulation costs and savings

As much as 15% of the heat in a room can be lost through uninsulated ground floors. 

Properly insulating your floor will not only warm your feet, it will also help you to save money. Insulating your floor and skirting boards can save as much as £80 a year and, if you can install it yourself, pay for itself in about two years through savings on your heating bills.

Floor insulation costs and savings
 Annual savingCost
Floor insulation - suspended timber floorFrom £30-£45 for a mid-terrace house to £75-£95 for a detached houseDIY: about £100. Professional: from £300 to £750
Floor insulation - solid floorFrom £30-£40 for a mid-terrace house to £70-£90 for a detached houseProfessional: from £950 to £2,200
Filling gaps between floor and skirting boardAbout £25About £10-£15

Options for floor insulation

Your insulation options depend on the type of floor you've got - suspended floors (typically with floorboards), solid floors such as concrete, or tiled floors.

Floorboard insulation (suspended floors)

Mineral-Woll-installation

Suspended floors can be insulated with mineral-wool rolls laid between the joists

Suspended floors, where the floorboards rest over joists so are, in effect, suspended above a void, are likely to lose more heat.

The easiest and least disruptive way to insulate floorboards is from underneath, if you have access via a cellar or basement. Here you are insulating the crawlspace (void) below the floorboards. When insulating from below, the insulation is secured with netting draped between and stapled to the floor joists.

If the floor is not accessible from underneath, you will need to deal with it from the top. This is more disruptive as it involves lifting the floorboards in order to fit insulation between the joists - a job that requires clearing out furniture and is therefore best combined with other messy tasks, such as decorating. 

Once the floorboards have been lifted, insulating material, such as mineral-wool rolls, is laid between the joists. Insulation can be made of various materials including sheeps wool, hemp and recycled plastic bottles, or rigid insulation boards. 

Insulating floorboards can be done as a DIY job or using a professional installer. If you want to do it yourself, materials can normally be purchased from a larger DIY store.

Floorboards will rot without adequate ventilation, though, so don't block under-floor airbricks in your outside walls.

Solid floor insulation

Solid floors such as concrete or screed should, in principle, lose less heat than suspended floors. But they can still be insulated by laying a new layer of rigid insulation on top. This would usually be covered by chipboard plus your desired floor covering. The insulation can be placed directly above the existing concrete or screed in the form of a 'floating' floor. 

This method will raise the floor level, so skirting boards and, potentially, some electrical sockets will need to be refitted and doors will need to be trimmed.

Laying a continuous damp-proof membrane beneath the insulation is advisable, taking care to overlap with any damp-proof course in the external walls. Damp-proof membranes can come flat or in rolls that look a bit like a big bin liner roll. They can be purchased from larger DIY stores.

It is possible to insulate a solid floor yourself, though it's a bit trickier than dealing with suspended floors and you might require an electrician if you need to move electrical sockets. If you want the help of a professional, find a recommended installer on Which? Local.

Floor insulation

Insulating between the floor and the skirting board can be easy and save about £25 a year

Skirting board insulation

Heat can also escape from the gap between your floor and your skirting boards. Filling that gap with a tube of sealant is a cheap, quick and easy solution. Sealant is available from DIY shops and costs just a few pounds.

Insulating tiled floors

Tiled floors can be extremely cold, as the material conducts heat very well. There is little you can do to improve the energy efficiency of a tiled floor, as they are so rigid and are usually laid on a concrete base.

As with wooden floors, tiled floors can benefit from checking for leaks. The skirting boards should be checked, as should the grouting between the tiles.

Insulating with rugs and carpets

Rugs on the floor will also help your feet to feel warmer and block off draughts, but it won't solve all the problems. 

Carpeted floors are usually the warmest floor type. The nature of carpet makes it a good insulator in itself. However, a thick, insulating layer of underlay underneath the carpet will further improve its insulating qualities.

Finding an installer

You can find an installer recommended by other Which? members in your area using Which? Local. The National Insulation Association website also lists local installers.

If you fit floor installation yourself, make sure you comply with building regulations for the minimum energy-efficiency values. Check with the relevant building regulation for where you live.

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