Rigid Foam Insulation Under Floor 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.

Rigid foam insulation under floor joists.

You can even place it under the foundation slab. Airtight insulation reduces heat loss through the rim joist band joist. Instead of installing the foam insulation between floor joists in the crawl space the foam board is installed against the crawl space foundation walls. That would need 90mm of rigid foam or 150mm mineral wool.

The insulation should cover the whole depth of the cavity and contact with the floor. Insulated rim joists place rigid roam against the rim joists then caulk along the insulation. Installers should push the insulation up and fasten it to prevent any void or gap between the floor and the material. Unlike fiberglass rigid foam insulation does not absorb water support mold or allow air to pass through providing that joints between boards are sealed with tape.

Rigid insulation is one of the best tools to reduce your energy costs. The insulation should be pushed tight to the underside of the floorboards. If it fits proper with no space between on either side of the board pick it up and put a thin layer of glue on. Fiberglass insulation and expanding foam seal the open top of hollow concrete blocks.

They keep your home at a comfortable temperature without the need to crank your heat. Next you will need to place the foam board insulation between each joist as a test. Rigid foam insulation also known as insulating boards provide high r values.