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A home or building which has a crawlspace can be handled in two ways. One, to utilize a method called sub-membrane depressurization. This involves installing a network of 4 inch corrugated pipe on the surface of the dirt floor. Then covering the entire dirt floor of the crawlspace area with a polyethylene vapor barrier( plastic sheeting ). We recommend a 10 mil thickness. The four inch pipe then exits to the outside where it is attached to a radon exhaust fan. When installing the vapor barrier for best results we recommend over lapping any seams 12 inches and seal them with duct tape or spray adhesive. Seal the plastic around any pillar or pipe etc...Also we wrap the plastic up any wall at least 12 inches and seal it to the wall with either spray adhesive or urethane caulk. As with an ASD system the exhaust of the fan must vent above the roof line. When the fan is activated it will draw the radon from below the plastic before it can enter the crawlspace and the structure. The radon will vent above the roof where it will quickly dilute to the outside air.

This is recommended for a structure with a crawlspace were the radon levels may be only slightly elevated,little ventilation exists and/or limited room to work. The idea is the same as the sub-membrane system except no vapor barrier is installed.The system shall remove the crawlspace air before it can enter the home through the floor.You may even install a network of 4-inch duct within the crawlspace when more than one cavity is present. The 4-inch duct would then attach to the intake side of the exhaust fan. The installation of additional vents creating more circulation of fresh air may work.This is always recommended first. You may even add a small ventilation fan to help circulate the air and introduce some fresh air. However be aware that in cold climates you may freeze the plumbing pipes.

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ASD Interior / ASD Exterior / Crawl Space / Commercial Mitigation Appliciations
Mechanical Ventilation / High Rise And Large Condominiums
Pre Construction / Home