Peach you are correct. I presented this as a code question in October 2008 and this was the response;
Code Question:
Code Edition: 2006 IRC
Code Section: R303.3 & M1507
Code Question:
Where a bathroom group consists of a bathtub/shower combo and a vanity with an adjacent toilet room separated by a door, is one exhaust fan near the bathtub/ shower sufficient?
The exhaust fan meets the 50 cfm intermittent requirement.
We currently have two exhaust fans operating in an Energy Star/LEED certified dwelling, one near the tub/shower and the other in the toilet room.
When the door is closed and both fans are on, the room is placed in negative pressure. This is creating a problem for us from the humid air in the attic above.
The bathroom group to include the toilet room is 62 square feet.
Answer:
Section 303.3 in the 2006 IRC requires ventilation in both bathrooms and water closet compartments. In the case that you have described the water closet is in a separate compartment and would require a separate exhaust fan. The remainder of the bathroom would also require a separate exhaust fan. I hope that this answers your question. If I can be of further service feel free to contact me.
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