Trained Eye


Dryer Vent in Attic



Recently, I purchased an older house in Kenora that appeared to be in good condition. However, prior to purchasing it I failed to look into the attic. Yesterday I decided to have a look and noticed that the dryer vent goes directly into the attic. Then I checked the crawl space under the house and the downstairs suite dryer vent goes directly into the basement.

My question is: Do you think that this is doing damage to the house? How would I change the vent that goes into the attic? The dryer is located in the middle of the suite away from any outside walls.

Thanks for your help!


At the beginning of every Pre-purchase inspection I give the client’s the following information: “One of the two biggest enemies of houses is moisture”. If you trace the majority of structural and sometimes cosmetic defects, the source of the problem is usually excess moisture and can be in the form or liquid water or water vapour. This damage can be from water infiltration through roofs, flashings, windows or leaky foundations, but may also come from the inside of the house, as well. Moisture produced from regular daily activities such as cooking, bathing, and clothes drying can be very substantial. If this moisture, in the form of water vapour, is not properly vented to the exterior, it can cause major damage to walls, ceilings, attics, and other building components. This is most important in attics and basements, as these areas are considerably cooler than the main living space of the house and prone to condensation. This is a rather long way of answering your first question with an overwhelming yes!

Older homes are often less of a problem, as far as moisture retention inside the “building envelope” because of the older windows, doors and walls. These older components normally have poor weatherstripping, seals, insulation, as well as wooden framing, sheathing and siding. All of these materials will be leaky, in relation to air movement in and out of the home, and will allow passive moisture escape to the exterior. This is also true with older attics, but unfortunately becomes more of a problem as upgrades are made. As widows and doors are replaced, and insulation added to walls and attics, more moisture will stay in the building or be forced up into the attic. This is when mechanical ventilation becomes critical.

Clothes dryers are designed to work properly with solid metal ducting, normally 4-inch diameter, attached to the rear vent and directed to the exterior of the home. Corrugated plastic ducting and flexible metal ducting may reduce the efficiency of the dryer. This is due to reduction of air movement from friction on the rough inner surface of the ducts and partial blockage as dryer lint adheres to the inside surface. Many manufacturers insist that solid ducting be installed, for proper operation.

It should not be difficult for you to install proper ducting in your attic attached to a roof-mounted vent hood or side wall vent hood, mounted on a gable end, if one is accessible. A roofer will likely be required to install the vent hood on the roof, which will have a round extension into the attic to attach your ducting to. Once this is completed, you must also insulate the ducting to prevent condensation and ice build-up due to the warm air from the dryer hitting the cold air of the attic.

The basement dryer may be more difficult to vent if it is the middle of the house. The easiest way to solve this problem is to move the dryer to an area close to the exterior walls of the house. Electrical dryer outlets in basements are easily moved, especially if the underside of the floor joists are exposed, or covered with a suspended ceiling. Once this is accomplished, proper metal ducting may be installed and the only remaining problem is creating a hole to the exterior.

This can be accomplished by either cutting a hole in the exterior wall between the floor joists or by drilling through the concrete foundation wall, itself. The first scenario may be easily done by the homeowner if the exterior wall siding is wood and the floor joists sit on top of the foundation walls. If the siding is stucco, metal, or vinyl or the floor joists are set in the concrete wall, going through the concrete is simpler. You will have to contract the concrete cutting to a professional. All that is required is a contractor with a diamond drill and access to a garden hose and electrical outlet. This job normally takes about and hour and should be inexpensive.

Once the hole is cut, a standard vent hood with a 4-inch diameter extension pipe can be installed from the exterior and secured and caulked to the foundation wall. Care should be taken to install this as high above grade as possible and in an open area clear of obstructions or wooden components. Once installed, the metal ducting can be attached to the vent hood with pipe clamps or duct tape and the excess moisture will be directed properly to the outside of the home.