Rigid Insulation Under Garage Slab

Is it worth it to insulate under a concrete slab.

Rigid insulation under garage slab.

That decision may hinge on whether the slab is heated but there s no agreement on what building codes require if anything. I am presuming there is a 4ft deep footing around the perimeter of the garage with no insulation. If this is the case then the frost will travel down the footing and make the floor cold and thus heat loss. Garage door insulation project guide.

Dealing with the edges the foam insulation and two layers of plywood can add as much as 2 inches of height to the garage floor. 4 10 2012 3 climate zones e301 1 6 5 8 4 slab r value table 402 1 1 insulation and fenestration requirements by component e402 1 1 climatezone slab r valued 4 10 2 ft 5 10 2 ft 6 10 4 ft 9. But when adding insulation to an existing slab the vapor barrier is laid over the top of the slab before the foam insulating panels are installed. Additional insulation is applied along the edges of the slab because that is a primary surface for heat loss.

A resource to point them to for example calculations is the article right sizing under slab insulation in the april 2014 issue of structure magazine. Get free shipping on qualified under slab foam board insulation or buy online pick up in store today in the building materials department. In climate zones 6 7 and 8 by any combination of vertical insulation insulation extending under the slab or insulation extending out from the building. Using rigid foam insulation around the perimeter of the slab to minimize heat loss seems like an obvious step but whether to place insulation under the slab is another story.

This compliance option is explained this way. Insulation located below grade shall be extended the distance provided in table n1102 1 1 namely 2 ft. R 7 7 rigid foam insulation model 310891 18 35 18 35. In climates zones 4 and 5 and 4 ft.