Kitchen exhaust fan, fresh air combat condensation

Hey there, time traveller!
This article was published 29/09/2002 (8438 days ago), so information in it may no longer be current.

Question: Ari: I read your column in the Sunday Homes on a fairly regular basis and find it very interesting and informative. Now I have a question for you!

My husband and I purchased a 17-year-old home last October. We have a problem with condensation on the windows whenever we do a lot of cooking. We never had this problem in our other home, but we always ran the stove fan when doing a lot of cooking, to remove moisture and smells.

Our other home was about 55 years old and we were surprised to be having this problem in a newer home. The only difference in the two houses, that we can think of, is the lack of an over-the-stove fan. We know the importance of removing excess moisture from the house and always run the bathroom fans, when using the showers. Would running the furnace fan constantly have a positive effect on reducing this problem? We did not do this in our other house, but we wonder if it would help.

We would like to install a fan over the stove in this house and have it vented to the outside. How big of a job is it?

The wall where the stove is installed is shared with the main bathroom. Running inside this wall is the vent for the bathroom fan. Can we connect the kitchen fan to the same vent as the bathroom fan? My instinct is that we can’t.

If we can’t connect the two fans, how big of a job is it to install a separate vent in the kitchen for the fan? The wall we would have to access has kitchen cupboards on it.

Are we going to have to take the cupboards all off the wall and cut into the drywall?

Finally, can you recommend a professional who would do this kind of work?

There would be electrical to be dealt with, also, as I assume this fan unit would have to have a separate power supply run up from the basement.

Thank you for taking the time to help answer this series of questions for us.

Regards, Coleene Major, e-mail

Answer:

The question of how to reduce excess condensation on windows, in cooler weather, probably is the most common question I received in the past year.

This is typical of the problems seen and may be foreign to the Majors because of the age of the home.

Old homes often have older, drafty windows and doors, natural-draft furnaces, older masonry fireplaces and poor insulation in the walls. These allow for a large amount of air movement between the living space and the exterior. These gaps will allow house air to escape and carry a large amount of moisture with it, and allow some fresh air in. This may significantly reduce the excess moisture that would be available to condense on cool windows.

Newer homes are much tighter and better insulated, which makes them more energy efficient but prevents the warm, moist house air from escaping the living space. Also, newer furnaces and fireplaces do not let as much warm air escape up their chimneys as do older units.

Moisture is added to a home due to normal daily activities such as bathing, cooking, cleaning, washing clothes and normal respiration and may cause condensation on cool areas such as windows, water pipes and walls. In extreme cases, this moisture can cause damage to components in the home, such as plaster, wooden walls and other areas.

For this reason, we have to find a way to remove some of this moisture from our homes. This may be done partially by natural ventilation from opening doors and windows, but some must be done mechanically, in the cooler months, when natural ventilation is less available. This can be achieved in many ways, often with expensive ventilators, but common sense is often the key.

Running exhaust fans, installing fresh-air intakes in basements and opening doors are some of the ways to reduce moisture. Running the furnace fan on continuous may help minimally with the condensation on the Majors’ windows. But, unless the moist air from the home is removed and fresh, dryer air from outside is brought in, it will not solve the main problem, which is lack of ventilation.

Adding a properly vented kitchen exhaust fan will improve the situation, especially on the kitchen windows, and will be moderately priced. A licensed electrician or licensed heating (HVAC) contractor may be the appropriate professional to call.

The fan must be separately vented from the bathroom fans and the vents can often be hidden in the cabinets or above, behind a valence. Care should be taken to ensure that plenty of fresh air is brought into the house at the same time that stale, moist air is exhausted, to prevent further problems.

Ari Marantz is owner/inspector of Trained Eye Home Inspection Ltd. and is the PR rep. for the Canadian Association of Home Inspectors — Manitoba (www.cahi.mb.ca). Questions can be e-mailed or sent to: Ask the Inspector, PO Box 69021, #110, 2025 Corydon Ave., Winnipeg, MB. R3P 2G9. Ari can be reached at (204) 291-5358.

trainedeye@iname.com