Insulation Thickness Between Floor Joists

This is to prevent the joist.

Insulation thickness between floor joists.

Pack precision cut perimeter insulation boards around the room between the joists and the walls to prevent heat loss through thermal bridging. The inside of the rim joist is sprayed from the sub floor to the bottom of the rim joist to drop the building envelope to the bottom of the joists. At least 25mm of the joist must be left exposed to ensure air circulation. The fiberglass will also need to be secured in place using wire mesh twine wood laths or other securing methods which can be an intensive project that adds to the overall cost.

When the basement or crawl space has vents installed insulating joist bays. This is a floor where the timber floorboards are attached to floor joists and the insulation suspended on timber battens between the joists. Encapsulating the floor system including duct work with thermo cloth and closed cell spray foam insulation creates a perfect wood framed floor system. The insulation should press right up against the floor between joists.

A semi rigid material is generally best as it can be cut very slightly oversized and squeezed in between the floor joists thereby ensuring no draught causing gaps. If the ground floor in question is of a suspended timber construction and whether this is a renovation or new build project then the insulation would normally be installed in the joist zone that is installed between the joists. As for insulating below the joists an insulating laminate insulation bonded to plasterboard such as celotex pl4000 or a separate rigid pir insulation board finished with a separate sheet of plasterboard can be securely fixed to the joists to provide an internal finish to the roof. Designed for easy handling and use between framing such as studs and joists making it among the best insulation for walls.

The insulation should be pushed tight to the underside of the floorboards. Gaps between the insulation and the floor can lead to inefficiency and heat loss. Alternatively battens can be secured to the underside of the. Best for unfinished walls floors and ceilings.

This perimeter insulation can be supported by blocks nailed to the underside of the joists. Joist bays the open spaces between floor joists are prime hosts for insulation under specific circumstances.