If you have an uninsulated solid ground floor, up to 10% of your heating energy is being drawn into the ground. This is less of an issue if you have suspended floors, although draughts from below can prove just as energy sapping.
If you do have a solid floor you have 3 basic options:
- lift up the existing floor, dig down 100-150mm, lay a screed, insert rigid insulation, and re-lay the floor;
- insulate on top of the existing floor and create a new floor (thus raising the floor by 50-100mm);
- simply to fit thick carpets with an underlay.
Newer homes may have a ground floor made of solid concrete. This can be insulated if it needs to be replaced, or can have rigid insulation laid on top.
Damp problems can arise with all of these options, and it is one of the few situations when an oil-based material is the best alternative.
Suspended timber floors can be insulated more simply either from underneath or by lifting the floorboards and laying mineral wool insulation supported by netting or boards between the joists.
You don't need to insulate the floors of upstairs rooms in your house if they're above heated spaces, but you should think about insulating any floors that are above unheated spaces such as garages.