7 Concrete Slab Foundation Insulation Tips 7 Concrete Slab Foundation Insulation Tips

Providing proper concrete slab insulation for your home's foundation will help keep your home warmer, while preventing insect infestation, gas accumulation and the buildup of mold and mildew. Note these 7 tips to insulate your concrete slab foundation effectively.

Provide Adequate Moisture Drainage Below the Slab

Make sure the slab foundation is installed on a firm, level bed of coarse gravel 8 inches deep for adequate drainage. In areas where soil moisture is prevalent, such as reclaimed swampland, install drainage pipes through the gravel 4 inches below the top of the gravel bed.

Choose the Best Method of Insulation

The 2 methods most often used for concrete slab foundation insulation are rigid exterior insulation and rigid interior insulation. Exterior insulation, most often made of foam board, is applied around the outside of the slab and its in-ground footing. Rigid interior insulation consists of building a "floating" concrete slab around a core of rigid foam sheeting. The floating slab insulation is a more effective barrier to termites and mold-causing moisture than exterior insulation. Both can be improved by adding a termiticide or pesticide to the foam insulation material.

Insulate in Warm Dry Weather

Apply all types of insulation to your concrete slab in warm dry weather, to minimize the moisture that becomes trapped in the insulation. Moisture in anaerobic conditions is the ideal breeding ground for unhealthy molds and mildew.

Insulate to the Maximum R-Value

The recommended minimum depth of concrete slab insulation is 2 feet. This gives an R-value of 5. This is fine for climates which have mild winters. Apply 4 feet of insulation to boost the heat insulation effectiveness of your concrete slab foundation to R-10, the highest rating. This insulation thickness will keep your home warm even if you have 120 days a year when you need to turn on your furnace or electric heat registers.

Insulate to Prevent Heat Loss at Door Sills

Apply a thicker layer of concrete slab insulation at spots where door sills will be placed. This will help reduce heat loss through exterior doorways.

Insulate to Prevent Insect Infestation

In addition to constructing a floating concrete slab as an insect barrier, cover it with a non-permeable membrane, such as rubber sheeting. Place this membrane around the entire perimeter of the slab as well as the top an bottom. If termites are a serious problem in your area, add aluminum termite shields around the slab edge, as a second physical barrier to chewing insects.

Insulate to Form a Gas Barrier

In homes with concrete slab foundations built on brownfield sites, previously occupied by an industrial or chemical company, the soil may contain low levels of gases such as radon or methane. Insulation to form a barrier to these gases is required by law. The insulation is composed of 3 parts: 1 layer of high density polyethylene (HDPE) in a grid, between 2 layers of low density polyethylene (LDPE). Be sure to install radon and gas insulation in dry weather, when the air temperature is over 50 degrees F. Install radon and gas insulation directly over the concrete foundation, and lay all other insulation materials on top of it.





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