Rigid Insulation Under Garage Slab

I am presuming there is a 4ft deep footing around the perimeter of the garage with no insulation.

Rigid insulation under garage slab.

This compliance option is explained this way. 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. If this is the case then the frost will travel down the footing and make the floor cold and thus heat loss. Conclusion with building owners growing desire to save money on heating and cooling costs and increasingly stringent energy codes contractors will be installing below grade and under.

Garage door insulation project guide. R 7 7 rigid foam insulation model 310891 18 35 18 35. 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. Additional insulation is applied along the edges of the slab because that is a primary surface for heat loss.

For under slab applications the rigid foam insulation typically should be installed over a gravel base with a poly vapor diffusion retarder between the gravel and insulation. That decision may hinge on whether the slab is heated but there s no agreement on what building codes require if anything. 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. 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. Insulation located below grade shall be extended the distance provided in table n1102 1 1 namely 2 ft. Is it worth it to insulate under a concrete slab.