Step by Step ProjectsTips from the ProsAffordable Remodels
My return air is routed through boxed in floor joists. Thee are gaps in the joints that sock in air from the crawl space. What is the best way to insulate. them.
Narrow gaps could be caulked. Wider gaps (not over 3/8") can be filled with foam or expanding foam. Gaps over 3/8" will require a repair.