Venting multiple dryers together
user-1002561
| Posted in Energy, Heating & Insulation on
I’m renovating an upper floor condo and the unit below is taking the opportunity with my open walls to install a laundry directly below my laundry. Both dryers will vent straight up through the roof. I’d like to join the two 4″ ducts and only have one roof penetration. Any thoughts on how this would effect the ventilation properties? Should I transition up to a 6″ rigid pipe after the junction? Would backflow dampers be necessary? If one dryer is gas and the other electric, does it kill this idea? Would it be simpler to keep two 4″ runs and accept another roof penetration? Any ideas would be appreciated. Thanks.
Ben
Replies
I have never had luck with combined dryer exhaust plenums. In fact I've had a lot of them replaced to individually vent, in order to correct problems associated with the plenums. I've never seen one succesfully avoid backdrafting over the long term. To be fair, these are installations of 5-20 dryers, not just two, but I believe the same principals apply to your situation.
Backdraft dampers would be necessary, the problem is the lint will build up and then prevent the damper from working well (or at all). Over time you'll get moist air from your neighbor's dryer into yours. Situations that will exacerbate this are 1)lint loading up the outlet of the common vent, thus making your dryer the path of least resistance for the air coming out of your neigtbors dryer, and 2) windy conditions outside can push back on the outlet periodically which force your neighbors air once again to the path of least resistance...your dryer.
Instead, run them individually, side by side, to create one larger flashing penetration instead of two small ones. Keep in mind these vents need periodic maintenance for cleaning of lint. Make sure access to the vent, and disassembly of vent, is easy.