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Sub-slab depressurization systems have been dubbed the “gold standard” by Health Canada. Indeed, where adequate sub-slab connectivity exists, sub-slab depressurization can dramatically reduce indoor radon levels. What about for the homes that don’t have great sub-slab connectivity? What about homes that have really, really poor connectivity? Where floor slabs are constructed on native soil, or well-compacted fill, drawing soil gas can be a challenge. Additional suction points may have to be considered and/or larger wattage fans.

In some circumstances, sub-slab depressurization may not be the best answer. We recently completed a diagnostic investigation in a home with very compacted sand below the floor slab. One suction point location was not going to suffice to depressurize the entire sub-slab, and we were looking at high wattage fans. Fortunately, the radon levels in the home were already below 200 Bq/m^3, and the owner was looking to trim the levels to as low as reasonably achievable. In this circumstance, our recommendation was to investigate the installation of a Heat Recovery Ventilator (HRV) unit for the home. While usually not suitable as a stand-alone technique to reduce high radon levels, HRVs can serve to reduce radon levels where only modest reductions are needed.

Installing sub-slab depressurization systems is what we do (and love to do). But sometimes the science tells us other avenues may be better fit.


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