Properly insulating your slab-on-grade floors not only will help you save on energy bills, but also will improve your home’s comfort. Cold concrete slabs can be a source of discomfort in a home. An insulated slab reduces heat loss, making it easier to heat. This reduction in heat loss helps moderate indoor temperatures.
Annual Energy Savings and Payback
Slabs lose energy primarily as a result of heat conducted outward and through the perimeter of the slab. Therefore, in most parts of the United States, insulating the exterior edge of the slab can reduce heating bills by 10%–20%. In climates with mild winters, slab insulation in a typical 1,800 square-foot home would save $50–$60 annually. Slab insulation with an R-value of R-10 for an 1,800 square-foot home typically could cost $300–$600 to install. Thus, the insulation would pay for itself in 5 to 10 years.
The investment in slab insulation is also economical as part of a mortgage. An insulation cost of $450 would add about $38 to the annual mortgage. However, the insulation would save over $50 annually in energy bills. Therefore, the savings exceed the additional mortgage cost from the beginning, resulting in an immediate payback.
Source: EERE, U.S. Department of Energy