Floor Insulation
Up to 15% of heat could be lost through the ground floor of your house or through rooms over unheated spaces such as garages.
What type of floor?
Floor insulation comes in two forms, suspended floor insulation and solid floor insulation. If your floor has floorboards laid over wooden joists with a void underneath then you have a suspended timber floor. Houses with air bricks at ground level typically have suspended timber floors to allow air flow under the floor.
Suspended floor insulation
It is important to make sure there is no wet or dry rot present in the floorboards before insulating suspended floors.
Suspended floor insulation is placed inbetween the joists below the floorboards. It is best installed from above, requiring the floorboards to be lifted. Typically, mineral wool insulation supported by wire of netting underneath is used A waterproof vapour control layer is placed over the joists and insulation so condensation doesn’t form on the joists, leading to rot, and draughts are eliminated.
Where it isn’t practical to lift the floorboards and there is enough room under the floor, they can be insulated from underneath.
Although this would have the same insulating value as insulating from above, a vapour control layer can’t be installed, so there is a greater risk of condensation and rot forming on the joists, which will be relatively colder after the installation of the insulation.
It’s always important to keep any vents and air bricks open after insulating the floor, to retain ventilation to the joists under the floor, to prevent the build-up of moisture under the floor which could lead to rot.
Solid Floor Insulation
If a concrete floor needs replacing, then this is an ideal time to insulate the floor as part of the replacement process.
An existing solid floor can be insulated by placing rigid boards over the existing floor that can withstand walking and furniture. A screed is then poured over this to form the new floor surface.
The level of the floor will likely be higher after the insulation has been placed on top of the existing floor, which can be disruptive, because anything located at or near floor level will have to be raised, such as skirting boards, bottoms of doors, cabinets or pipework for radiators, etc.
Costs and savings
The Energy Saving Trust calculates that typically floor installation in the UK can cost between £520 and £1,300 depending on the specific circumstances.
The average mid-terraced house can save up to £30 on energy bills per year and the average detached house can save up to £70 per year.
Spray Foam Insulation
Some companies offer to spray insulating foam directly under the floorboards, sometimes using a robot where space is very tight.
This isn’t recommended because it can trap moisture in the joists which can cause them to rot. The presence of spray foam insulation can also affect your ability to get a mortgage on the property and once it’s applied, it can be a very difficult and costly job to remove it.
Suspended or solid floor?
Contact us for advice on local suppliers and what to ask them when providing a quote.