During a remodel you find that a bathroom group's vent rises into the attic, turns, and simply ends in the open attic space several feet from the roof sheathing. What does the plumbing code require of that vent?
- AIt is acceptable in a ventilated attic, because attic ventilation carries the sewer gas out through the soffit and ridge vents
Attic ventilation moves air slowly and inconsistently, and the sewer gas has already entered the building by the time it reaches the soffit. Nothing in the code recognizes an attic as outdoor air.
- BIt is acceptable if the open end is fitted with a screen and located at least 6 inches above the attic insulation
A screen keeps animals out of an opening that should not exist. Height above insulation is an air admittance valve rule and has nothing to do with an open vent terminal.
- CIt must be fitted with an air admittance valve at the point where it now ends inside the attic space
An air admittance valve is a one-way device that admits air only. It may be permitted in some locations, but it is not the fix for a vent that was supposed to reach outdoor air, and installing one does not vent positive pressure out of the system.
- It must be extended through the roof or through a sidewall so that it terminates in the outdoor air
Why D is correct
Terminating outdoors is what separates a vent from a hole in the drainage system. Extending it through the roof or through a sidewall at the required clearances puts the sewer gas outside the building envelope, which is the entire purpose of the terminal.
What this question is testing
Whether the candidate understands both functions of a vent terminal and knows that an interior space, however ventilated, is not an acceptable termination point.
On the job
Vents left short in attics are common in additions and in do-it-yourself work, and the symptom the homeowner reports is an odor in the upstairs hallway on windy days or a stain on the attic side of the sheathing from condensed moisture. It is a cheap fix while the attic is accessible and an expensive one after insulation is blown in. Whenever you are in an attic for any reason, follow the vents to the roof jack.
Memory technique
An attic is inside. Vents end outside.
Exam tip
A vent has to end outdoors. Any option that lets it end inside the building envelope is wrong regardless of what is added to it.
Where to look it up
IPC Chapter 9, the vent terminal provisions covering roof extensions and terminals near openings. The UPC states its own terminal heights and clearances, so verify in your adopted code.