The House Detective by Barry Stone, Certified Home Inspector
Dear Barry: In a past article, you said, “It is not legal for a clothes dryer exhaust vent to terminate within the confines of a building….” and you cited Section 504.3.1 of the Uniform Mechanical Code. Does this mean that the dryer vent diverters sold in hardware stores and used to provide extra heat in a home are illegal too? Marshall
Hello Marshall: Several companies are currently marketing clothes dryer vent diverters. These fixtures consist of a vent duct connection and a small water reservoir. As the dryer exhaust passes through the diverter, the moist air from the clothes dryer vents into the room, while the lint is captured by the water in the reservoir. Manufacturers such as Dundas Jafine praise these devices as sources of indoor heat in winter. Advertising claims include “No need to drill holes to vent your dryer….” and “Ideal for apartments, condominiums and mobile homes.” What they fail to mention is that the building and mechanical codes specifically require that clothes dryers be vented to the exterior.
There are three primary reasons for exterior venting of a dryer. With a gas dryer, the primary issue is safety because the exhaust contains combustion byproducts that could be dangerous to breathe if vented into a home. The manufacturers of dryer vent diverters are aware of this and only recommend use with electric clothes dryers. But the likelihood that some homeowners will install diverters with gas dryers is undeniable.
Another problem with dryer vent diverters is moisture condensation in homes. All of the wetness in the clothes that were just washed is being expelled from the dryer vent. In dry climates, this added air moisture might be an advantage. In areas with moderate to high humidity, the moisture from a dryer could promote condensation and the growth of mold.
The third problem is the potential for lint build-up in the home; a potential fire hazard. This can occur if the water level in the reservoir is forgotten and allowed to evaporate. Lint can then bypass the diverter and vent into the home.
The building code prohibits the installation of unapproved fixtures in mechanical systems, but it does not prevent manufacturing companies from producing and selling such items. Other examples of products that enable homeowners to violate the building code are corrugated connectors for the drain pipes under sinks, submersible refill devices for toilet tanks, and electrical outlet adaptors that enable you to insert three-prong plugs into two-prong wall receptacles.
The free market allows these devices to be made, but the authors of the building code have good reasons not to sanction their use.