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
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.