Featuring America's Home Inspector: Nationally Syndicated Columnist, Barry Stone

What’s Wrong With Plastic Dryer Vents?

The House Detective:  by Barry Stone, Certified Home Inspector

Dear Barry:My handyman did some repair work under the house, and he said that I have the wrong kind of exhaust duct for my clothes dryer. It’s made of white plastic and looks like a long accordion. The dryer has been venting perfectly for over ten years, so I can’t see any reason to spend money replacing it. In your opinion, what is wrong with this kind of dryer duct?  Ben

Dear Ben:  Corrugated plastic ducts are often used to vent the exhaust from clothes dryers, but there are three things wrong with this type of dryer duct:

1)  Exhaust from a clothes dryer can be very hot, especially if you have a gas dryer. Repeated heat exposure to paper-thin plastic can be a significant fire hazard. If a fire were to begin under your house, it could spread very quickly throughout the home. Therefore, a dryer vent duct should be made of non-combustible material.

2)  Plastic dryer ducts become brittle after years of use. Eventually, they crack and fall apart. Then, all of the clothes dryer exhaust vents into the crawlspace, and since no one is likely to notice the damaged duct, this could go on for years, with lint build-up occurring daily and moisture condensation occurring whenever the weather is cold. Dryer lint is highly combustible, which again, raises the issue of a fire hazard. Moisture condensation under the house can cause fungus infection on wood members and can promote the growth of mold.

3)  Corrugated dryer exhaust ducts, whether they are plastic or metal, tend to collect lint. As lint accumulates, the inside dimension of the duct becomes smaller, and this creates resistance to airflow, causing the clothes dryer to overheat. Once again, we have a fire hazard due to a substandard vent duct.

The solution is to install a 4-inch diameter, smooth, sheet metal exhaust duct that terminates on the outside of the building. The fittings should be secured with tape rather than screws because screws on the inside of a dryer duct can collect lint. The maximum permissible length of the duct is 14 feet with a maximum of two 90-degree turns. For each additional turn, two feet should be subtracted from the overall length. If greater length is needed to reach the outside of the building, a booster blower should be added to the duct.

Clothes Dryer Steaming Bathroom

The House Detective:  by Barry Stone, Certified Home Inspector

Dear Barry: : Our laundry is located on the second floor, directly adjacent to the bathroom. Whenever I run the dryer, the bathroom becomes very humid if the door is shut. I’ve also noticed something like black soot on the bathroom walls. I wash it off, but it always comes back. What could be causing the humidity and the soot, and what can I do to resolve this?   Debbie

Dear Debbie: Here are two possibilities: The vent duct for the clothes dryer may be connected to the bathroom vent duct in the attic. This would allow steam from the clothes dryer to enter the bathroom through the ceiling vent.

Another possibility is disconnection of the dryer vent inside the wall or ceiling of the bathroom. This would cause the moisture from your clothes to vent into the wall or ceiling cavities, raising the humidity in that room.

Another concern is that the “soot” on the walls could actually be black mold, caused by the excessive moisture condition. If so, this would raise health concerns for your family.

To evaluate and resolve this situation, three things need to be done:

1)  A licensed contractor should investigate the path of the dryer vent to determine whether it is disconnected or not properly vented to the exterior.

2)  The wood framing should be inspected to determine whether moisture exposure has caused fungus infection and dryrot.

3) The area should be evaluated by a qualified mold inspector to determine if mold is the problem and if mold remediation is needed. Air samples should be taken from wall cavities to determine whether there is mold behind the drywall.

Safety Concerns in Electrical Panel

The House Detective by Barry Stone, Certified Home Inspector

Dear Barry: We recently purchased a home. During the negotiations, we asked the sellers to replace the electrical panel due to safety concerns disclosed by our home inspector. The sellers agreed to have this work done. On the day that the escrow closed, the escrow officer told us that the new panel had been installed without a permit. After moving in, we applied for our own permit at the building department. But the new panel did not pass inspection. We emailed copies of the failed inspection notice to the sellers, their agent, and our agent, but no one has responded. What should we do? Niki

Dear Niki: According to the National Electrical Code and the International Residential Code, it is illegal to perform electrical installations without a permit. It was the responsibility of the sellers to have this work done according to safety code requirements and with the approval of the local building department. Likewise, it was the responsibility of the agents to inform you of the status of the work before the close of escrow, not after.

If the sellers and agents are unwilling to address your concerns, a wake-up letter from a real estate attorney may be needed. Certified mail on legal stationary tends to be more stimulating than common email. Of similar effect would an ethics complaint at the local Board of Realtors office.

Heating Your Home With a Clothes Dryer

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.

Moisture from dryer ducts could lead to mold or fungus growth

The House Detective by Barry Stone, Certified Home Inspector

Dear Barry: We live in a 6-unit apartment building, and the dryer exhaust ducts for all six of the laundry rooms blow into my attic. Every few months, the landlord’s maintenance man goes into the attic to remove the lint that clogs the neighbor’s dryer vents. He insists that this is not a problem, but I’m afraid it is causing the moldy smell in our apartment. What is your opinion of this situation? Wendy

Dear Wendy: It is not legal for a clothes dryer exhaust vent to terminate within the confines of a building, either in the foundation crawlspace or the attic. Section 504.3.1 of the Uniform Mechanical Code states that: “Moisture-exhaust ducts for domestic clothes dryers shall terminate on the outside of the building…”

There are two reasons for this requirement: 1) Moisture condensation can promote the growth of fungus or mold; 2) The accumulation of lint can pose a fire hazard. Therefore, someone should extend the dryer vents in your building through the nearest exterior wall or through the roof.

The moisture from six laundries could definitely be causing mold or fungus growth in your attic. To determine possible mold infection, a professional mold consultant should conduct a thorough survey of your home to determine the types of mold that may be present and the proper means of remediation if hazardous mold is found. At the same time, a pest control operator should inspect the attic for fungus infection of wood framing and resultant dryrot.