Fill gaps larger than 1 4 in.
Rigid insulation between floor joists.
Cut rigid foam insulation into strips with a table saw or a circular saw.
This method can be hundreds of dollar less than the cost of using the commercially applied spray foam.
Instead of installing the foam insulation between floor joists in the crawl space the foam board is installed against the crawl space foundation walls.
Run a bead of acrylic caulk around each section of foam to form an airtight barrier.
How to finish a basement.
Seal and insulate using rigid foam board insulation.
A do it yourself friendly method for sealing and insulating the rim joist or band joist area is to use rigid foam up against the rim joist.
When the basement or crawl space has vents installed insulating joist bays.
Gaps between the insulation and the floor can lead to inefficiency and heat loss.
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.
The insulation should press right up against the floor between joists.