Poor fan venting causes mold buildup
Q: I read with interest your article on venting a bathroom fan. I live in Austin, Texas, and my daughter lives in Illinois. The builder told her there are no codes concerning the venting of the bath fans, and he is unwilling to make the repairs under the home’s warranty. Her fairly new home has mold buildup on the ceiling and outside wall where the bath fan is located and I’m worried about the health of my granddaughter. The builder simply placed the fan’s hose in the roof’s overhang and I know it is not venting properly. I am an engineer and I can’t find any information to help me in my battle with the builder. Can you help?
A: I found two references that might help. Section 504.1 from the 2012 International Mechanical Code states:
“Installation. Clothes dryers shall be exhausted in accordance with the manufacturer’s instructions. Dryer exhaust systems shall be independent of all other systems and shall convey the moisture and any products of combustion to the outside of the building.”
There is also the 2009 International Residential Code, section M1502.3, Duct termination. “Exhaust ducts shall terminate on the outside of the building. Exhaust duct terminations shall be in accordance with the dryer manufacturer’s installation instructions. If the manufacturer’s instructions do not specify a termination location, the exhaust duct shall terminate not less than 3 feet in any direction from openings into buildings. Exhaust duct terminations shall be equipped with a backdraft damper. Screens shall not be installed at the duct termination.”
Not all states or municipalities within a state enforce the codes, but the codes are the minimum (note minimum) standards allowable for safe construction and to protect the health and safety of the home’s owner. Check with local and state building authorities to see what codes, if any, are enforced in your area.
If the builder is not willing to help, you should have a contractor remove the damaged drywall and any damp or wet insulation, then replace the fan’s venting system according to the codes.
If the fan’s vent pipe is in an attic space, insulate the metal vent pipe to prevent future condensation problems.