Installing Bathroom Exhaust Fans

Originally posted 2010-03-10 07:24:56. Republished by Blog Post Promoter

Every home has a bathroom and many homes have had bathrooms added. Many home owners have installed their own bathrooms and there is one area that many don’t seem to understand, the bathroom exhaust system.

The Ontario Building Code requires every bathroom to have either a opening window or an exhaust fan. Personally I think you should install an exhaust fan any way, it just makes sense to remove all that moisture and humidity from your house.

Do not go to Canadian Tire and pick a piece of that plastic wire lined pipe for your attic exhaust duct, it does not meet the code requirements. Buy a proper kit instead, it will included the properly insulated pipe you need.

Here are the requirements, as per Part 9 of OBC

(1) ….may be of combustible material provided the duct is reasonably airtight and constructed of a material impervious to water.

(2) Exhaust ducts shall not discharge into heated or unheated enclosed spaces.

(3) Where an exhaust duct passes through or is adjacent to unheated space, the duct shall be insulated to not less than RSI 0.5 (R3)

So my interpretation is that the duct has to terminate outside of attic and it has to be insulated. A lot of people suspend exhaust ducts from existing roof vents, but that can raise two issues; 1. Is it now blocking required ventilation from attic. 2. Is the duct installed high enough in the existing vent to ensure moist air is actually leaving attic.

While doing Home Inspections I found some attics have bathroom exhaust duct suspended below an existing roof vent which would allow warm air to condensate and then drop back into attic.

Many bathroom exhaust fans also terminate at the roofs soffit. When doing this always ensure that the vent covers louvers point away from the house. I have seen many houses where the moist air is exhausted towards the house and simply rises through the vented soffit and rises up the rafters or trusses leaving a trail of moisture.

Just because they sell a product at a store does not mean it is the right product for the job. Take your dryer vent for instance, many people use the same plastic duct on their dryers. If you read your dryers manufactures installation instructions you will find that it actually has to be installed using the rigid metal duct or the flexible metal duct, not foil, according to meet the manufactures requirements.

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