Floors

In most climates, insulation with a minimum thermal resistance value of R-19 should be installed beneath the floors of heated rooms located over unheated areas such as basements, beneath stairwells and stair landings between heated and unheated areas, and above garages, porches, or areas with an overhang subject to outside temperatures. Insulation can be omitted from floors over heated basements or heated crawl space areas if the foundation walls are fully insulated. Foundation walls of heated basements typically do not need to be insulated, except where 50 percent of the wall is exposed to outside air or if the basement contains a habitable room.2