What is Sub-Slab Depressurization
Health Canada has described sub-slab depressurization as the “gold standard” of radon mitigation methods (Health Canada, 2010). The principal is similar to a range hood fan. When we are frying food on the stove top and want to keep the odours from permeating through our homes, we flip on the range hood fan. The fan draws air from within its zone of influence and expels it outside. In the same way, sub-slab depressurization uses a specialized radon fan to draw soil gas (and radon) from below the floor slab and discharges it outside. The fan creates a lower pressure under the slab than in the basement. This depressurization means that the flow of gas will not be into the building.
There are many factors to be assessed in the design of a sub-slab depressurization system, but perhaps the most important is the degree of connectivity of the sub-slab material. This will dictate the size of the radon fan required and the need for multiple suction points. Fan sizing and suction point locations are not guess work. They are determined based on the results of a diagnostic investigation. Diagnostic investigations will be the subject of our next post.
Health Canada, 2010. Reducing Radon Levels in Existing Homes: A Canadian Guide for Professional Contractors .