When Creativity Sets In- Bathroom Ventilation Fans
In the wonderful world of home inspection we often to get to see some wonderfully creative moments. Here was such an example.
Someone rightly thought they should upgrade the ventilation and add a bath fan to their older home. Now I often suggest that adding a bath fan as a great idea to help control moisture and aroma when it comes to bathrooms. But if you do so, then you need to actually do it correctly. So what exactly is correct?
So for fun lets jump into the code. This will give the guidance we need to properly execute this upgrade.
From the 2015 IRC (with Washington State Amendments per the Washington Administrative Code (WAC)).
Links the actually WAC’s-
https://apps.leg.wa.gov/wac/default.aspx?cite=51-51-0303
https://apps.leg.wa.gov/wac/default.aspx?cite=51-51-1507
From the IRC (With Washington amendments)
M1507.4 Local Exhaust Rates
Local exhaust shall be provided in each kitchen, bathroom, water closet, laundry room, indoor swimming pool, spa, and other rooms where water vapor or cooking odor is produced. Local exhaust systems shall be designed to have the capacity to exhaust the minimum air flow rate determined in accordance with Table M1507.4.
M1507.4.2 Local exhaust controls
Local exhaust systems shall be controlled by manual switches, dehumidistats, timers, or other approved means. Local exhaust system controls shall be readily accessible.
M1507.2 Recirculation of Air
Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space or other areas of the building.
Now we have to jump to another section of the code that deals with ventilation, exhaust openings and terminations.
R303.4 Minimum ventilation performance
Dwelling units shall be equipped with local exhaust and whole house ventilation systems designed and installed as specified in Section M1507.
Exception: Additions with less than 500 square feet of conditioned floor area are exempt from the requirements in this code for Whole House Ventilation Systems.
R303.5.2 Exhaust Openings
Exhaust air shall not be directed onto walkways. All exhaust ducts shall terminate outside the building. Terminal elements shall have at least the equivalent net free area of the duct work.
R303.5.2.1 Exhaust ducts
Exhaust ducts shall be equipped with back-draft dampers. All exhaust ducts in unconditioned spaces shall be insulated to a minimum of R-4.
R303.6 Outside Opening Protection
Air exhaust and intake openings that terminate outdoors shall be protected with corrosion-resistant screens, louvers or grilles having an opening size of not less than 1/4 inch (6 mm) and a maximum opening size of 1/2 inch (13 mm), in any dimension. Openings shall be protected against local weather conditions. Outdoor air exhaust and intake openings shall meet the provisions for exterior wall opening protectives in accordance with this code.
So you can see ducting your bath fan to the plumbing vent is not only not allowed but a very bad idea. In some certain conditions you may actually draw sewer gases back into the home. Now though this may be unlikely still not a great idea and just not allowed.
In addition to the creative ducting we also got some creative wiring, but we can save that for another day.
As a home inspector in Wenatchee and Chelan county if you ever need some help or like to as me a question on building codes and construction practices feel free to contact me.
If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.
NCW Home Inspections, LLC is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…
Your Wenatchee and Chelan Professional Real Estate, Home and Structural Pest Inspection Service
Coordinator & Instructor- Fundamentals of Home Inspection- Bellingham Technical College
Former WA Home Inspector Advisory Licensing Board
www.ncwhomeinspections.com 509-670-9572
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