By pulling the screen showed and guaranteeing the insulation is tightly bound into space you can decrease heat loss through the floor without needing to lift a single floorboard. Unfortunately, if your home doesn’t feature a basement or a cellar, but the floor is still suspended, floorboards and any floor finishings will need to come up. Since it’s a big job to empty a room of furnishings to gain access to the void below, we recommend that this is done alongside other big jobs like plastering or painting.

Like insulating a floor where a basement or cellar provides access to the joists, you need to lift the floorboards and put them to one side before laying rigid insulation boards in the joist spaces. Cut each piece of insulation board to just slightly smaller than the joist space you’re going to fit it into, this will provide friction for a tight fit, so no air can escape through the side gaps.

You can use insulation roll like popular natural insulation sheep’s wool by fitting inexpensive insulation netting underneath the joists as in the picture to the right. Drape the netting as low as needed to accommodate the thickness of the insulation roll then roll the insulation out, as usual, taking care to make sure it extends to the width of the joists.

Please be aware of airbricks in outside walls. Floorboards will rot if airbricks are covered as there will be no ventilation! These should be at least 2 inches below the bottom of the insulation before the hardcore.