DIY: Outside Air Recirculation

Identify a location along the exterior wall of your home that is directly opposite an unfinished area of the basement, near your furnace. If your washer and dryer are in the basement, examine the spot where the dryer-vent pipe exits the building through the home's siding. The vent you will install is the same size and shape as the dryer-vent pipe, and you may be able to mount the new vent pipe next to the existing dryer vent.

Drill a hole through the siding, at the same level as the existing dryer-vent pipe, with the 4-inch hole saw. The hole must penetrate the building, and lead directly into the basement near the furnace.

Mount the dryer-vent hood pipe through the hole, into the basement. Secure the vent hood in place with small screws at each corner of the vent hood. Remove the aluminum flapper, which is under the aluminum hood. The make-up air vent must be unobstructed to operate properly.

Inside the home, caulk the joint between the vent pipe and the home's framing with siliconized acrylic caulk. The caulk will prevent water or insect infiltration around the vent pipe.

Add additional pieces of 4-inch warm-air vent to the vent hood to extend the pipe through the basement to the furnace. Nail the perforated metal strap to the floor joists to hold the vent pipe in place. Bring the pipe to within 24 inches of the home's central HVAC unit.

Slide the 90-degree elbow onto the end of the pipe, and point the elbow downward. Add one more 36-inch piece of warm-air duct onto the pipe so that the pipe points downward toward the furnace. This make-up air duct will now supply clean air into the home as the furnace heats and cools the home throughout the year.