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Old 10-16-2017, 10:59 AM   #1
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Bathroom Vent Fans??


Working on finishing off a basement bathroom. It's a bit of an odd shape as I'm working with some extra room in a 100yr old house. The bathroom is just over 5' wide, but essentially ~28' deep. (it's really about 22' deep, but it makes an L bend at the end where I'm putting a fairly large walk in shower. To add to the mix, because this space was dug out after the house was built it has retaining walls that sit anywhere from about 1-2' in from the exterior walls to about 3' in. These account for the entire length of the space and I'm making some built ins out of this space as well as some sort of hidden storage. I'm guessing since this space is sort of open to the foot print, I need to account for it in the square footage. In the more hidden parts, I'm lining them with cedar boards to help control critters to a degree and I assume they'll also help absorb some extra moisture....hopefully not in a bad way.

Since the toilet and the shower are on opposite ends of the bathroom and due to the distance, I am thinking I'll install two seperate vent fans, one above the toilet and one near the shower. I actually already have the holes on the exterior walls due to an old furnace"?" vent and the other is currently attached to my clothes dryer, but I'm planning on shortening the run for it and moving it to another wall, so that hole will also be there. Is this a good idea or bad idea? Should they be wired together or independently....I was thinking I'd wire them seperate so if someone needed to vent a bad odor, that would be right there by the toilet and the switch by the door. Then if someone took a shower, they would have a switch nearby for easy access as well.

Now how many cfm's do I need? I believe I read once 1 cfm per sq foot. Then add about 50 for each fixture such as toilet, tub, shower. I was looking at the Broan 110 series fans and the AE110, I listened to at a local store, and it was a nice quiet sound and it would handle 110sq ft. I was wondering if two of those would be sufficient, but to be honest, I'd kind of like a heat lamp style near the shower. We have one of the two bulb style in the master bath and it's kind of nice in the winter just to provide an extra touch of warmth when you step out and are drying off and I figure in a basement, since they are typically cooler, it might even be nicer.

I'm so far not having much luck on finding the heat lamp style that handle much over 70cfm. In the summer, I replace the upstairs heat lamp with LED bulbs since I don't want the extra heat. I believe some of these vents also have a heater built in, maybe that's the ticket...hmm! Then to add to the confusion, it seems some of the Broan (and probably others) 110 series have a built in function that turns the fan on automatically if it senses moisture. I think I've also seen switches for them that do this as well. Being in a basement, that seems like a great idea, but I don't know how well they work OR if they are purely automatic or something that is switched on/off.

Can anyone point me in a good starting direction to this? I know I've provided a lot of info. I'm really close to wanting to install the vent near the toilet, so I can figure out my lighting there as well as put up the drywall in this area. I'm a bit further out on the shower end.

Thanks for anything...
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Old 10-16-2017, 11:05 AM   #2
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Re: Bathroom Vent Fans??


Maybe I should add the ceiling construction is 2x6 joists. I add this because I was looking at a Panasonic fan/heat combo unit that says it fits 2x8 construction. In the rest of the basement I also had to fur the ceiling height down with 2x material to clear a few items, level it out, and get it so the can lights had a bit more depth. I'm trying to avoid doing that in the bathroom, but once again, now is the time to figure that out so I can start hanging ceiling drywall.
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Old 10-16-2017, 11:29 AM   #3
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Re: Bathroom Vent Fans??


I just made notes as I read so will post and catch what I missed next time.

It's not square footage it's cubic feet that the fan has to deal with.

Absorbing some of the moisture does no good if that moisture will have to dry back into the same space. Exhausting the moisture is what the fan accomplishes and requires longer run times which the damp wood may increase.

Due to the larger space two fans would be good and locating one at each end kind of helps. However, if each has its own switch then both would need to be sized for the total volume. Probably the one near the shower should have the delayed-off timer, but maybe both.

Remember, you will need as much air coming in as you are exhausting out, under the door or other paths.

Ultimately all air you exhaust will be replaced from outside. If an automatic sensor turns on your fan when it is raining out then it will be pulling damp air back in, hmmm.

Bud
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Old 10-16-2017, 03:21 PM   #4
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Re: Bathroom Vent Fans??


Cubic Feet makes more sense. I'll figure that out. Ok, well when I look that up, this is what I'm finding...
**Ventilation rates based upon eight air changes per hour are generally suggested. For most bathrooms this works out to one CFM per square foot of bathroom area. For example, a 7' x 10' bathroom would require a 70 CFM fan. A 50 CFM rating is recommended as a minimum for bathrooms 50 sq. ft. and smaller.**

As for the wood, the purpose isn't to absorb the moisture, it might do that it might not. I'm guessing being in the basement it might absorb some. but to be honest I have a fair amount of other hard and soft woods down there for projects I've been doing and none of them seem to have a high moisture content, at least not enough to alter their usability. I just thought it might absorb some, but likely not enough to really matter.

I get what you are saying about pulling damp air back in, hmm...maybe I'll stay away from the moisture sensor feature. Being an old house it isn't very tight, but of course I'm probably changing some of that as I finish this basement space off. There will be a gap under the door, but nothing real large. Wonder if I should add a register to allow air transfer from another room such as the laundry room, which is kind of on the other side of the wall. I could do it very inconspicuously.

As for the two fans, again, I hear what you are saying about both being able to turn the air over, I guess they could both be wired to come on together, the issue I have there is people forgetting to turn on/off. In our main floor bath, i put the fan on a timer, which is great, no forgetting. I haven't yet done this for the 2nd floor and people either don't turn it on or forget to turn it off. I suppose a 3 way switch might work for the fan, but I'll have to investigate about adding a timer to a 3 way. I like the idea of it being able to be turned on from either location, being as there is distance.
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Old 10-18-2017, 12:04 PM   #5
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Re: Bathroom Vent Fans??


Well, one online calculator says a 126fcm fan, if I play with the size a bit due to the storage behind, then I get about 152cfm fan. The only thing is they aren't asking about the fixtures in the room and the place I got the info in the post above made it sound like that should be taken into account.

In any case, Panasonic has a pretty nicely rated 80/110cfm fan (FV-08-11VF5). I think I'll buy this fan for above the toilet and though it isn't truly large enough for the entire room, all I really want it for is to help eliminate bathroom odors and it can be kicked on to help if the 2nd one isn't doing it's just fast enough.

From there I need to find a 150cfm+ fan that will work great near the shower. Problem is they all seem to be too tall for my 2x6 ceiling joists. I'm guessing they could probably be installed on a wall, but I'll do research on that. Thanks!
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Old 10-18-2017, 02:29 PM   #6
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Re: Bathroom Vent Fans??


I haven't shopped for a fan in awhile, but options may have changed. Do some searching to determine how you will control the two fans and related lights. Some fans may have some of the smart features built in, like delayed off.

As for size I don't see a big problem going with the smaller fan especially if the larger has a fit problem. Check what size duct they use when rating them. My 140cfm is with a 6" duct and it drops to 130cfm with the 4" option while noise goes up.

I have my duct installed and the shell for my main bathroom but haven't addressed the controls. Initial plan is to keep mine near the entrance, but it isn't 20' plus feet away (10 x 12).

Just a quick thought might be to put the fans on their own timers and switch the lights as desired. When a fan is needed they just push the "time to run" button and forget it, like 30 minutes. Then the fan can never be left running beyond some set time.

Bud
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Old 10-18-2017, 03:00 PM   #7
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Re: Bathroom Vent Fans??


I plan on two switches, one for each fan. The lights will be on their own switch as well. The main bath overhead lights on one switch, near the door with the first fan, timer. Then I'll have a switch by the sink for the sconces, which will surround the medicine cabinet. I will also have a switch for the makeup vanity, which I plan on building in towards the rear and then near the shower, I'll have a switch for the shower fan, again timer, and a switch for a light inside the shower.

Probably sounds like a lot of switches, but they will be near their intended use area, so they'll be spread out. Also, no reason to light the vanity if not being used. Tempting to put an outlet or two on that switch, so things like a curling iron or what not are less likely to get left on. Hmmm.... Same goes with the shower, etc....I'm kind of wondering if I just wire the shower light into the shower fan switch, less likely for the fan to be left off, plus if on a timer, it'd cut down on extra long showers! I have an 8yr old that likes to try to take 20min+ showers!!
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Old 10-18-2017, 10:38 PM   #8
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Re: Bathroom Vent Fans??


In post #4 you mentioned an interest in using a 3 way switch. Some searching and I'm not finding a simple option, other than wireless (I think). Since mine will wrap up this winter I will need to get the wires in place so some searching, planning, and final decisions are in order. If I come up with something I will share, but don't wait for me, too many projects going.

The solution I believe, too late for me, is to have the delay as part of the fan unit. Turn power off and fan continues for set amount of time. Would need a remote for control or a step ladder, not convenient.

If your 8 year old with the long showers is your daughter, it gets worse, longer, steamier, and more frequent. Mine are all grown and gone, they do visit.

Done for the night

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