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Will this bath vent routing work?

3K views 5 replies 3 participants last post by  organick 
#1 ·
We have a ranch style home with gable ends. I want to install a vent into the bedroom's bathroom that has a tub/shower combo. This bathroom is 4.5' W x 9.5' L x 8' high. Web calculator says it needs a 45.6 CFM vent fan but I want to be sure the mirror doesn't fog up when I take a shower. I want to run the vent in the attic, over the bedroom to the gable end. The total distance from the fan to the gable end will be about 14 feet.

Questions are:
1. Which CFM vent fan should I buy so the mirror doesn't fog up? (I want a quiet one.)

2. Is a 14' vent run too long for a bath vent?

3. If 14' is OK, what diameter "smooth" vent pipe should I use?

4. What slope does the vent pipe need toward the gable end for condensation run off?

Thanks,
HRG
 
#2 ·
I aim for at least 1.5 times the square footage in CFM. So I would say at least a 75CFM fan. For quiet fans check Broan, Panasonic. If doing more than one bathroom look at Fantec.

14' is a very long run. If all straight, up the size of the fan. Each elbow adds 6' to the effective length of the pipe run. Use 3 or 4" smooth wall(rigid) pipe(aluminum OK), depending on what the fan outlet is.

As long as it slopes slightly away, that is OK. Insulating the pipe helps keep moisture liquid.
 
#4 ·
Thanks for your very informative info. There will probably be two elbows. One to go up from the fan and one to go horizontal to the gable end. I guess I should go with a 100+ CFM fan if I go with the 14' run and I'll use smooth wall 4" aluminum pipe.

Thanks again,
HRG
 
#3 ·
I would really think twice about venting to the gable. your much better off venting out through the roof. running a 14 ft ridgid vent to you gable is just asking for trouble in my opinion. How will you secure it? It def needs to be insulated or it will drip condensation somewhere. i would go through the roof. Its really not a big deal to do.
 
#5 ·
Thanks for taking the time to respond. I want to avoid punching a hole through our roof since it would void the warranty for our recent roofing job. I could call the roofing company and have them do it but that would involve more $$$ than I want to spend for this bathroom vent. So I guess it has to be the gable end vent, or stay the way it's always been.

Thanks again,
HRG
 
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