How much R-value should be installed under concrete floors in basements?
Although the Ontario Building Code (OBC) does not require insulation to be installed under non-heated floors in garages, basements, or other rooms, the OBC does require insulation to be installed under heated floor systems. It is, however, best practice to insulate and isolate the entire building envelope. The entire building envelope includes the ground.
The OBC requires R10 be installed under radiant heating systems; therefore, it is safe to consider installing R10 insulation under any concrete floor.