Reusing existing vents
I have installed three Panasonic Whisper Green bath fans on the top level of my townhouse. All three fans require at least four-inch vent pipes. The old fans were all three-inch slinky pipes.
I plan to use four-inch smooth pipe with the new fans but would like to reuse the openings that already exist in roof. Would it be acceptable to gang two of the runs together with a Y and exit the roof with a single piece of pipe? I was considering this approach and transitioning to a six-inch pipe for the final leg of the exhaust run.
I also have a question about repurposing a six-inch double-wall run of pipe that used to be connected to a gas furnace in the attic. (I have foamed the attic and converted the HVAC to all-electric.) I would like to use this pipe as a fresh air supply. Would that be allowable, or should I replace it with single-wall pipe?
Also… I wanted to reroute the end of the double-walled fresh air pipe and terminate it somewhere in the top floor living space. The HVAC systems and/or a bath fan would then be used to pull in fresh air. Alternatively, I have considered routing the fresh air pipe to a nearby return that runs to a Daikin ducted head installed in the attic. This approach would probably be easier to implement, and I think Daikin supports a ventilation-only mode.
Last bit of information, I have located a SensorPush wireless humidity and temperature sensor in the attic to monitor conditions. If the humidity levels start to elevate, I will probably install a dehumidifier and ventilator or try using a vapor diffusion port to keep conditions in a safe range.
So any advice?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part