Horizontal Insulation: Continuous insulation is applied directly to the underside of the slab and extends inward horizontally from the perimeter for the distance specified, or continuous insulation is applied downward from the top of the slab and then extends horizontally to the interior or the exterior from the perimeter for the distance specified. For example, 'R-10 at 36 in.' means that insulation with a rated thermal resistance of 10 must be installed and that the insulation must extend a distance of 36 inches form the top surface of the slab. The R-value specification in standard defines both the rated R-value of the insulation and the depth or width of the insulation. For unheated slabs, insulation may or may not be required depending on your climate zone, whether or not the project is residential, and which edition of Standard 90.1 is being referenced.

Heat losses from heated slabs are greater than that of unheated slabs because the temperature is warmer. Heated slabs-on-grade will feature hot water pipes or coils embedded within or beneath the slab to provide space heating. Unheated slab-on-grade floor: a slab-on-grade floor that is not a heated slab-on-grade floor.

Heated slab-on-grade floor: a slab-on-grade floor with a heating source either within or below it. Let's unpack the issue in the context of ANSI/ASHRAE/IES Standard 90.1 - Energy Standard for Buildings Except Low-Rise Residential Buildings.įirst, the standard defines two classes of slab-on-grade: Slab-on-Grade Insulation Requirements in ASHRAE Standard 90.1

Ashrae standard 90.1 2013 pdf