Bath exhaust fan
#1
11-03-19, 08:22 PM
Bath exhaust fan
My 18yo fan stopped working today so thinking I'l probably need a new one. The bath is 6 ft x 8 ft with an 8 ft ceiling. Is there a recommended cfm for that size?
Haven't checked the switch yet....I have one of those timer switches on it so possible the switch is bad and fan ok, I'll check it first.
Current unit is a Nutone 50cfm 696N.
Haven't checked the switch yet....I have one of those timer switches on it so possible the switch is bad and fan ok, I'll check it first.
Current unit is a Nutone 50cfm 696N.
#2
11-04-19, 04:42 AM
Group Moderator
Most bath fan manufacturers do have recommended bathroom sizes for their fans.
Most fans have replaceable parts so you can likely fix what you have.
Most fans have replaceable parts so you can likely fix what you have.
#3
11-04-19, 05:00 AM
If it's an 18 yo fan it's probably time to replace it anyway. A good rule of thumb is 1 CFM per square foot or a minimum of 48 CFM in your case. My opinion is that more is better. I would go bigger. I would also try to get the quietest fan that fits your budget.
#4
11-04-19, 12:41 PM
Member
For moisture removal I recommend a minimum of 100CFM even for the smallest of bathrooms. I have 145 cfm in my 5x8 and 100 in my 4x6. I wish both where bigger. Code for commercial buildings is 50cfm per fixture. So shower and toilet is 100CFM.
#5
11-04-19, 05:16 PM
Thanks for the replies. The timer switch turned out to be bad so popped in a new one, cleaned up the fan and its good to go...except I need to get bigger screws to hold the timer in the box, the originals won't grip.
I saw an "upgrade" kit for my particular fan where you replace the motor, fan and the cover and use the old enclosure. 10 min install for a fan thats 60 cfm and 1/2 the noise. I may go that route.
I saw an "upgrade" kit for my particular fan where you replace the motor, fan and the cover and use the old enclosure. 10 min install for a fan thats 60 cfm and 1/2 the noise. I may go that route.
#6
11-05-19, 04:25 AM
Group Moderator
Yes, it's much easier to replace the guts than it is to install an entirely new fan. Most are nailed to the framing during construction so it can be a bugger to get the old housing out and install a new one.
#7
11-05-19, 07:51 PM
Looked at fans today at store. Lots of options, most are way quieter than what I have(4.0 sones). Thinking about going with a 110 cfm/1 sone unit, maybe that will keep my mirror clear when using shower? The 50 cfm has to run an additional 10-15 mins after turning off shower to clear the mirror.
I have attic access and don't mind having to enlarge the hole for bigger unit. I see some have a damper in the ductwork, or is that standard across the board on all models? What about the humidity sensing fans, do they work well? I don't need one with any kind of light in it. And the ones with heaters, wouldn't most of the heated air just go out the vent?
I have attic access and don't mind having to enlarge the hole for bigger unit. I see some have a damper in the ductwork, or is that standard across the board on all models? What about the humidity sensing fans, do they work well? I don't need one with any kind of light in it. And the ones with heaters, wouldn't most of the heated air just go out the vent?
#8
11-06-19, 04:37 AM
Group Moderator
Going to a larger fan foot print will make installation easier as you won't have to repair any sheetrock. Hopefully you can do everything from down below but it's good that you can get into the attic if needed. One annoying issue I often run into is if they stapled the wire tight and close so there is no slack to move it to the new fan.
Most fans come with a damper. It's usually part of the plastic adapter that goes on the outside of the metal fan box and is where the duct attaches.
You are correct. A heater in a ceiling vent fan is almost useless. At best the heat stays near the ceiling. Worse, the fan just sucks out the heat you just paid to generate.
Most fans come with a damper. It's usually part of the plastic adapter that goes on the outside of the metal fan box and is where the duct attaches.
You are correct. A heater in a ceiling vent fan is almost useless. At best the heat stays near the ceiling. Worse, the fan just sucks out the heat you just paid to generate.
#9
11-07-19, 12:41 PM
Member
Fans should run at least 30 minutes after showering to remove humidity. Only time it isnt needed is if your house is leaky
#10
11-07-19, 04:32 PM
Group Moderator
The fan for my shower is on a mechanical timer. Just give it a twist to set how long you want the fan to run and it turns off automatically when the time is up. It makes it easy to run the fan for 20 or 30 minutes after your shower.
#11
11-16-19, 08:18 AM
My new Leviton push button timer is working fine. They have 2 similar looking models of the timer, one is for incandescent and one like mine mentions fans so its more heavy duty. I was looking at fans today at Home Depot and noticed all the Nutone fans have "Made in USA" in big print on the box whereas all the other manufacturers have "Made in China" in smaller print on their boxes so you know which brand I'll be getting. I saw one thats 100 or 110cfm and .9 sones that looked good. Maybe they'll put some on sale for Black Friday or send out a 10% coupon around the Holidays. My old fan is working fine so I can wait a bit. 
#12
05-20-20, 08:33 PM
I've finally got a new fan ordered, getting a Nutone 110cfm unit for my 5x8 bath. It has a 4" exhaust and I currently have a 3" on my builder fan that looks like it goes nowhere. I say that because the hose goes over to the outside wall but disappears into the ceiling insulation. Looking all around outdoors I cannot see anywhere it exits. So I suspect it just terminates inside my attic.
I've got a 4" Nutone exhaust kit I'm planning to install. It has a hood that they say to just cut a 4 1/2" hole to run the pipe through , then cut a section out of the siding, then screw the outlet cover into the exterior wall. My house is vinyl sided. Will that be water proof enough? Seems like it would not be? It will be on a vertical exterior wall about 10 feet above grade. I've seen the J block mounts that have a square plate that attaches under the siding then a finish plate that snaps on on the siding exterior. That would be more work for me to install and a little more expense but would that be better?
I've got a 4" Nutone exhaust kit I'm planning to install. It has a hood that they say to just cut a 4 1/2" hole to run the pipe through , then cut a section out of the siding, then screw the outlet cover into the exterior wall. My house is vinyl sided. Will that be water proof enough? Seems like it would not be? It will be on a vertical exterior wall about 10 feet above grade. I've seen the J block mounts that have a square plate that attaches under the siding then a finish plate that snaps on on the siding exterior. That would be more work for me to install and a little more expense but would that be better?
#13
05-20-20, 11:46 PM
Member
but would that be better
The duct will have a flange so it would seal behind the siding. Another option would be the vents that mount under the roof soffit, no water issues to deal with a a cleaner look!
#14
05-23-20, 12:32 PM
I didn't mention it, but my soffit is vinyl as is the siding. I saw a video that said a soffit vent for a bath fan was not a good idea for ventilated soffit like I have because the moist air coming out of the vent will tend to be drawn back up into the attic. I have a vent coming I can install under the vinyl siding with a locking trim ring on the outside for a clean and tight look. I think I'll go that route.
Now, next question: I'll have about a 4-5 foot run of 4" from the fan to the vent. Its through an unfinished unheated attic, should my hose be insulated? The furnace does live in the attic though about 10 feet away from the fan and this is in GA.
Now, next question: I'll have about a 4-5 foot run of 4" from the fan to the vent. Its through an unfinished unheated attic, should my hose be insulated? The furnace does live in the attic though about 10 feet away from the fan and this is in GA.
#15
06-26-20, 06:51 PM
New on the left, junk on the right!
Very clean looking I think?
Epilogue: I spent a ridiculous amount of time today installing the new fan and the new PROPER vent for it. I have a nice wall vent with double flappers and about a 7 foot run straight from the fan to the wall with a 4" hose. Remember the old builder grade fan had a 3" hose that ran over to the wall area and seemed to stop. I looked a little better for where it exited but never found where it goes outside. It made a severe 90 degree turn right at the wall that couldn't be good for airflow. Instead of just fastening the flapper door to the vinyl siding, I decided to use the J mount they supplied under the vinyl siding. I only had to take about a 6 foot section of siding loose to fasten the J mount. I'm certain by doing this I have a much better seal against the weather and insects etc.
Time will tell how well it keeps the humidity down in the bath and the mildew off the shower curtain. So far I'm very pleased. Thanks for the help everyone!
#16
07-10-20, 01:24 AM
Member
Most residential Codes require 50 CFM intermittent (as needed) or 20 CFM continuous (24/7). Refer 2015 IMC Table 403.3.1. What a lot of people don't realize if that a "50 CFM" fan rarely delivers that much with duct connected to it, especially when "Dryer Hose" is used (That's prohibited for use as an exhaust duct, BTW). Bottom line: Buy an "80 CFM" fan for 50+ CFM in the Real World.
You should do quite nicely with your 110.
You should do quite nicely with your 110.
