In this video, Ask This Old House plumbing and heating expert Richard Trethewey shows how to control humidity throughout the house all year round.
How to Install a Whole-House Dehumidifier
- In the attic, attach four steel hanging bars and the metal pan from the collar ties. Position the pan very close to the air-conditioning unit.
- Set the whole-house dehumidifier in the metal pan.
- Cut a square hole in the hallway ceiling and install a new return-air grille.
- Attach a flexible return-air duct to the port on the end of the dehumidifier.
- Secure the duct to the roof framing with plastic straps.
- Cut the duct to length, then attach it to the return-air grille installed in Step 3.
- Cut a new supply-air duct fitting into the air-conditioning unit.
- Connect a flexible supply-air duct to the fitting. Attach the opposite end of the duct to the existing air-conditioning duct system.
- Run a new PVC condensate line from the dehumidifier to the outdoors.
- Install the dehumidifier's filter; be sure to replace the filter every two to three months.
- Mount a humidistat to the wall beside the existing thermostat.
- Start by setting the humidistat for 35 percent humidity, then adjust as necessary.