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Insulating Concrete Slabs For Radiant Floor Heating Systems

Investing money in the right type of insulation will save you money in the long run. Regardless if your new home or addition is utilizing a form of radiant floor heating, it would be wise to invest in slab insulation. As covered in earlier blogs, heat moves to cold. Insulation helps to slow down the thermal transfer of heat, allowing us to remain more comfortable and have lower energy costs.

Not all forms of insulation are created equal. Resistance to heat flow –commonly referred to as R- value – will vary depending upon the thickness and material type of the thermal insulation. Insulation underneath concrete slabs is normally a form of extruded polystyrene. This is sold in 4’ x 8’ sheets and comes in 1” and 2” thicknesses. My suggestion is to invest in the 2” polystyrene (R-10) for slab insulation – especially if you live in a cold region of the country. You will typically see a return on this investment within your first heating season.

Insulating along the perimeter of the slab is just as important as it is to insulate underneath it. As depicted in the illustration below, the perimeter of the building can be a source of heat loss. This is a critical step – especially on slab-grade homes – where the outside edge is exposed to cold outside temperatures.

insulating under a concrete slab

Be careful of the “snake oil” types of insulation. These systems are made up of a thin, bubble wrap, foil-type insulation blankets that claims to be have a high R-value. This type of insulation is cheaper than extruded polystyrene, but it is not a good choice for slab insulation. I think it should be referred to as “bubble crap” because its manufacturer has no business claiming that this product is a good form of insulation.

Make the right choice the first time, and invest in concrete slab insulation that you’ll pay for only once, and will pay you back over the lifetime of your home.