If your basement is on a slab, cut a 4-inch circular hole in the concrete near one of the corners of the basement. Remove about 3 gallons of the gravel and substrate under the slab to give the radon gas a space to accumulate.
Insert a 1-foot length of 4-inch PVC pipe into the hole and seal around the edge of the concrete with silicone sealer.
If your home has a crawl space, cut the membrane to just cover the soil under the crawl space to the edges of the house, leaving 4 inches spare at each edge. Cut a 2-inch hole in the center where the PVC pipe will go.
Make several cuts from the 2-inch hole out to a 4-inch diameter. Add a T to a 1-foot length of 4-inch PVC pipe and insert the pipe from underneath through the hole so that the T stays under the membrane and the cut strips of plastic form a sleeve around the pipe.
Secure the sleeve with duct tape to make an air-tight fit. Spread the membrane out over the soil in the crawl space and fasten the edges to the house footings by taping the plastic to the footings and then nailing strips of lumber over the tape.
For a basement installation, route the PVC pipe along the wall up to the joists and along the joists to an outside wall. Drill a 4-inch hole in the joist faceplate and route the PVC pipe through the hole to the outside For a crawlspace installation, route the PVC pipe up to the joists and along the joists, through a crawlspace vent to the outside.
For both installations, choose an outside wall location where the pipe and radon fan will not spoil the look of the house.
Route the PVC pipe up the side of the house to just below the roof. Install the radon fan at the end of the pipe, just below the roof.
Route the PVC pipe from the radon fan around the eaves and at least a foot above the roof line. Install the pipe vent at the end of the pipe to prevent rain and snow from entering the pipe Run the system for 24 hours and then re-test for radon.
If the level has not dropped to an acceptable value, additional holes and pipe branches in the slab or in the membrane may be necessary.