You can insulate under insulate under floorboards to help make a home more energy efficient. Insulation will keep the warmth in and stop drafts from escaping, especially if you use a draught proofing seal around the edges.
The way you insulate under your floorboards will depend on the type of flooring and access underneath. Suspended timber floors consist of floorboards nailed to joists and often carried on’sleeper’ walls of brick and need ventilation to avoid moisture build up. If the underside of a suspended floor is not ventilated it can lead to rot and fungus growth.
Insulate Under Floorboards: Improving Energy Efficiency
If you have subfloor access then bulk insulation such as rolls or batts is ideal. Rigid foam boards are also a good option for under concrete floors where there is no subfloor access.
A more time consuming but effective approach is to lay a vapour barrier under the floor before you fit the insulation. This will reduce the amount of moisture that gets into the joists, creating a controlled internal environment and significantly increasing the performance of the insulation.
When fitting the insulation ensure that it is snugly fitted, as gaps will dramatically decrease its effectiveness. You may need to side-nail 25 mm x 25 mm timber battens or partially drive galvanised nails through the insulation and into the joists to hold it in place. Any narrow gaps between joists and perimeter walls should be filled with expanding urethane sealant. This will prevent the insulation sagging and creating a gap that can allow air to escape, particularly in cold climates.