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Two bathrooms need exhaust fans

5 years ago

folks

100 year old house with slates that often leak so time for a new shingles roof. I also have two bathrooms in the 2nd floor right below the attic. Looking from the attic, the distance between the light fixtures in each bathroom are about 18 feet apart. I want to get exhaust fans installed as in the winter time in NYC, all the bathroom smells and moisture come into the bedroom and smog up the windows. Since I'm getting a new roof, I can choose to install a single fan in the attic that connects to both bathrooms like this https://www.familyhandyman.com/bathroom/exhaust-fan/use-an-in-line-fan-to-vent-two-bathrooms/view-all/

Or if the more reliable way is to vent out each exhaust fan in the bathroom to the attic individually, I can have the roofer create two exit points and connect using smooth walled duct. I do get a 20 year labor warranty with the roof so if there are any leaks, he will come and fix them

Secondly, there is quite a bit of debate for the humidity-sensing exhaust fans vs ones you turn on/off with the switch. I personally favor the humidity-sensing ones but also don't want them to go on automatically if it's a 90% humidity day and raining outside

Thx

Featured Answer

millworkman

5 years ago

They need to be vented thru the roofd to the exterior of the building not the attic. You don't need or want to be dumping hot moist air into your attic.

Comments (6)

First home
Original Author
5 years ago
Yes the plan is vent through the roof. My question is since I'm getting a new roof, should I create two openings in the roof and each connected to its own pvc pipe back to the 2 exhaust fans? Or should I use something like fantech where the fan is sitting in the attic and I'll need one opening in the roof? Supposedly it makes it quieter since fan is in the attic but I know the panasonic units are also fairly quiet. I'm looking for something that will last a long time

https://www.amazon.com/Fantech-Premium-Bathroom-Exhaust-Vent/dp/B01COPXHVW?th=1
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Thanks all, I finally got access to the condo's message board and got some help from another resident. He said the ductwork was there and said something about a "door" in the fan unit. I poked around inside of it again and lo and behold, a small piece of sheet metal fell off the side of it and there was the duct! The sheet metal piece had a piece of tape on it that I think may have been a hinge, of sorts--so that it would flap open when the fan was on and then fall back over the duct opening when the fan was off to keep drafts out. But a thick coating of greasy dust had kept it from working properly, and also made it hard to see that that's what its function was. The duct opening is only about 1x2", not the big 3" or 4" round opening that I was thinking it should be. It's still not a great fan but at least it's not blowing all of the air right back into the room! And I will have to figure out how to put that flap back on once the weather gets cold, but I have a bit of time before that will be necessary. PS-- no window in that room, unfortunately...
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As for fan-lights in the shower, it seems ineffective to try to remove water vapor laden air from the shower since most of it will condense on the walls before that can happen anyway. My goal is to remove humid air from the vanity area and allow fresh air drawn from the door undercut to reduce fogging of the mirror and window glass. The entire bathroom will eventually dry out if you use a fan with a built in timer and/or constant low speed feature like Panosonic's WhisperGreen series. I have yet to find a fan-light combination that performs as well as separate units. Here are my criteria: no CFL or LED lamps (LED inappropriate in a bathroom; CFL inappropriate in a house) Max sound rating .8 sone max grille size 13x13 flush with ceiling variable speed fan with timer Panasonic makes a recessed spotlight-fan combination (FV08VRL1) but it uses a CFL. I suppose a halogen PAR lamp could be substituted because the CFL is probably only needed to get an EnergyStar rating but I am not comfortable recommending it. To reduce fan noise it is important to reduce back-pressure by using larger metal ducts.
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Is there an existing fan you're replacing? If a new install, you need to connect it to ducting that leads to outdoors, not just into the attic. An alternative with more size flexibility would be to put in a small HVAC grill that runs through the ceiling drywall, to which you snugly connect flex duct on the back side, that then runs to an inline fan (like what Fantech makes) mounted in the attic. Then connect flex duct to the fan's output to run to where the air exits the attic and you're done. Remember to include a damper in the line. Search for "Valterra Heating and A/C vent register" to see an example. Or get an HVAC ceiling grill with a boot behind it to mount. With a Fantech inline fan, you'll not hear much fan noise but a small grill and high air flow will produce air flow noise. Maybe a long and narrow one with a larger surface area would work? Can you mount an exhaust fan on an exterior wall?
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First home
Original Author
5 years ago
anybody?
zneret
5 years ago
last modified: 5 years ago
Panasonic fans are indeed quiet. I guess the question you have to ask is how much it is to cut vents in the roof (gables are better if you can use them) and how long the duct run is. If joining to one vent result sin a long run, it maybe (most likely will) be less effective.

Whatever piping you use, don't use flexible hose. I've never seen bathroom piped with plastic pipes. Usually galvanized metal.

I am starting to favour timers myself for bath ventilation fans.
First home
Original Author
5 years ago
i checked my roof and there are vents over both the bathrooms. I'm guessing they are fixture vents since there is no current exhaust fan. Is the best thing to do simply connect the exhaust fan duct to the vent that's already in place?
alex9179
5 years ago
That's probably a plumbing stack. You can't use that, if it is.

Roofers will tell you to reduce the number of penetrations because that reduces the number of potential leaks.

HVAC will say that the CFMs are reduced with longer runs and the venting may end up inadequate.

Have you consulted your HVAC company? Start there for what's advisable in your situation.

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