Rules, regulations, laws, they all are basically a set of defined parameters. We live by the rules, play by the rules and die by the rules or so I've heard it said. Yet in life there are unwritten rules. Like you don't date your best friends ex-girl friend or wife. Nope, you just don't do it.
With house construction the "rules" are called codes. Kind of like not dating your best friends ex, it's a bro code. Codes define the dos and don'ts of constructions. Much of these rules are safety oriented, but not all. There are also many installation parameters that do not fall under the "rules" or at least those particular rules.
An example of this I find in Connecticut construction is bathroom venting. Quite often I find the bathroom vents installed in the soffit like that in the picture. Those two vents are in a new house. While this installation method is not specifically forbidden by the rules, it is first and foremost a bad practice.
There are several things that are simply wrong with placing a bathroom exhaust in a vented soffit. The first and what should be the most obvious reason is that these soffits are vented. Soffit vents are the intake side of the attic ventilation system. They work in unison with the ridge vent, which is the exhaust side. Therefore when warm moist air is expelled from the bath vent, a good portion is drawn right into the attic through the soffit vents.
I have heard many times that the moisture will not be drawn into the vents and if so it will have little to no effect. I present exhibits A & B. The first photo is of a roof deck near the soffit on a condo that was about 3 years old at the time. Notice the black fungal type growth on the wood, notice the rusted roof nails. The next photo shows the ceiling insulation stained from condensation dripping from the exposed roofing nails near the vents.
The other problem I have run into with bath vents in the soffit are cold bathrooms. Since this particular configuration does not allow for a closeable termination, which is not written in da rules, air can and often does back vent through to the bathroom. I'm sure there is nothing quite like experiencing an icy January breeze cooled porcelain throne in the middle of the night. The thought sends a chill down to my nether regions.
So while there are no rules that specifically forbid the practice of putting a bath vent in a vented soffit, it's simply a bad practice, like double dipping, and shouldn't be done.
James Quarello
Connecticut Home Inspector
Former SNEC-ASHI President
NRSB #8SS0022
JRV Home Inspection Services, LLC
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