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Information you need to do building and remodeling projects right the first time and protect the safety and value of your home.

Prevent Mold with Proper Kitchen and Bathroom Ventilation

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Mold poses significant health risks and can affect the value of your home. Mold is difficult and costly to remove. Prevention is the best way to deal with mold. Proper ventilation and removal of moisture from your bathroom and kitchen are great ways to prevent mold growth in your home. If you observe excessive mold or mildew build up around your windows and vents, you may want to check your home's ventilation system.

The 2008 Oregon Residential Specialty code has adopted new requirements for kitchen and bathroom ventilation. This code is required for all new construction. The kitchen and bathroom ventilation sections are also highly recommended for all kitchen and bathroom remodels. For more information, talk to a licensed and bonded contractor.

The new requirements for kitchen ventilation are:

  • Stove exhaust hoods must be metal and at least .016 inch thick
  • Exhaust systems cannot recirculate air inside the home, they must vent to the outside
  • Exhaust hoods must circulate air at 25 cubic feet per minute (cfm) for continuous fans (fan systems that are always on) or 150 cubic feet per minute (cfm) for intermittent fans (fans attached to a switch)
  • There must be 24 inches between a cooking surface and any wood or other combustible surface (except for down draft exhaust systems or combination microwave oven/ventilating hoods)

The new requirements for bathing facilities and spas are:

  • Continuous fans shall be rated at a maximum of 1.0 sone (a sone is a sound rating, the lower the number the quieter the sound)
  • Intermittent fans shall be rated at a maximum of 3.0 sone
  • Attic fans that are located 4 feet or more from the air inlet grill are exempt from sone requirements
  • Continuous bathroom or spa fans must circulate air at 20 cubic feet per minute
  • Intermittent bathroom or spa fans must circulate air at 80 cubic feet per minute (fans attached to a timer or de-humidistat)
  • Half bathrooms (without showers or bathtubs) must have fans that circulate 50 cubic feet per minute
  • The venting system must be controlled by a de-humidistat (a sensor that detects moisture in the room), timer, or other automatic control
Also, for both kitchen and bathroom fans it is important to know that the amount of duct work (the distance that the air is vented) has a big effect on the amount of air the fan circulates: the more duct work, the less air circulated.
The 2008 Oregon Residential Specialty Code has a table (M1507.4) that contractors can use to determine the size of the fan needed to circulate air for the length of duct work that will be used.

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