Alberta lifts onerous slab insulation requirements

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Alberta has waived onerous underslab insulation requirements that brought the hydronic heating industry to a virtual standstill when they came into effect in November 2016.

On Oct. 4, Alberta Municipal Affairs published a Standata (14-BCV-019) that provides a variance to National Building Code Regulation 9.36 that increased underslab insulation requirements for radiant floor heating systems from the one inch or R-5 required by the CSA B214 hydronic installation code to R-16 or about four inches.

The variance requires a minimum RSI 0.88 (R-5) for a radiant floor heating slab in contact with the ground where the floor is fully below the frost line and RSI 1.32 (R-7.5) where the floor is above the frost line. Standard industry practice has been to install 1.5-inch (38 mm) R-7.5 insulation.

“There is sufficient evidence that indicates that the current underslab insulation code provisions are excessive and jeopardize the availability of hydronic heating as an option for Albertans,” the Standata states. “This type of system has become increasingly popular in Alberta for homeowners who want added comfort and control in their heating zones, savings through lower heating bills, and a decrease in their environmental impact by making smart green building choices.”

The additional insulation provides little increase in energy efficiency. Going from R-5 to R-16 reduces heat loss through the slab by only 1.27 percent but makes the insulation cost about 50 percent of the installed cost for the radiant floor slab, reports the Standata. As well, the thick insulation can result in structural issues that can only be dealt with through costly modifications to building design.

The variance does not remove the insulation requirement from Section 9.36 of the Alberta Building Code, but it allows, as an alternative, the reduced insulation. The variance covers the entire province.

Alberta Municipal Affairs officials are also encouraging the federal National Research Council (NRCan) to change the underslab insulation requirements in the National Building Code to “allow for hydronic heating installations while also supporting Alberta’s energy efficiency goals.”

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