Is it Necessary to Insulate Under a Slab in a Superinsulated House?
INSULATION LOCATION & EXTENT for SLABS - CONTENTS: Here we answer the question: do I need to insulate under my basement slab in a super-insulated house?Do we insulated just the slab perimeter or the whole floor? Can we use uninsulated floor slabs to help with cooling? Critical insulation under radiant floors & passive solar floors. Advice for building insulation priorities
Also, if wood flooring or carpeting isn't planned, underslab insulations will make the floor feel warmer to bare feet.
See FLOOR, CONCRETE SLAB CHOICES.
And if your concrete floor is a "floating slab" without below-frost-line footings, such as our thoughtless contractor installed in Northern Minnesota, insulation under the entire slab may be critical to avoid pumping most of your heat into the ground during the heating season.
If you are installing a radiant heat basement floor system, insulation under the floor slab and the location of the heating tubing are critical -
see RADIANT HEAT FLOOR MISTAKES. --DF
The material of choice for insulating a slab would be high density, closed-cell rigid foam board insulation, such as extruded polystyrene.
Thermally break the interior finish of the basement floor from the concrete (e.g. with wood or solid foam board) to increase comfort and to control condensation if that's a problem in your area during summer months.
If you are installing a radiant heat basement floor system, insulation under the floor slab and the location of the heating tubing are critical - see RADIANT HEAT FLOOR MISTAKES.
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