Designing Kitchens and Bathrooms - Bathroom exhaust fan question.
Doityourself.com community forum was created to provide answers to all questions related to home improvement and home repair. Doityourself community can help you find information about how-to topics on small fixes to large remodeling projects. With comprehensive how-to content and expertly moderated community forums DoItYourself.com makes it easy to tackle even the most complex home improvement projects.View Full Version : Bathroom exhaust fan question.
wendans
03-30-08, 03:34 PM
Let's see if I can explain this properly. We have had a downstairs bathroom for over 25 years. We just recently had to remove our shower, which led to the tile being removed etc. Any way we are now doing a complete remodel. We have never had a problem with mold or mildew on the ceilings and we have never had an exhaust fan either. I would like to put one in but can't find any way of doing it. Let me try to explain why starting from the far side of the room and working my way across.
Beings this is the basement, in this room there are ducts. The heating duct takes up the first two options for placing any exhaust fan ducting. The next set of joists are taken up by the ducts for the furnace to the outside air. The next joists have a 5" duct for our tankless water heater vent. This is probably our only option for our fan ducting so it would have to be a narrow fan that would take up only 8" and is also a low profile. It would also have to attach on the lower two inches of the joist because there is the pipe there. I will send an attachment if I can to show you what I mean. The next joist would work but our bathtub drain is right in the way of the outlet to outside. The final one would work but it would have to go in the shower because the return vent takes up the space where it could go. I just may not be able to get one in unless someone knows where to find a small one some place. If it does not have a big CFM then it would be worthless anyway so I hope someone knows what I can do.
Attached Images
Beings this is the basement, in this room there are ducts. The heating duct takes up the first two options for placing any exhaust fan ducting. The next set of joists are taken up by the ducts for the furnace to the outside air. The next joists have a 5" duct for our tankless water heater vent. This is probably our only option for our fan ducting so it would have to be a narrow fan that would take up only 8" and is also a low profile. It would also have to attach on the lower two inches of the joist because there is the pipe there. I will send an attachment if I can to show you what I mean. The next joist would work but our bathtub drain is right in the way of the outlet to outside. The final one would work but it would have to go in the shower because the return vent takes up the space where it could go. I just may not be able to get one in unless someone knows where to find a small one some place. If it does not have a big CFM then it would be worthless anyway so I hope someone knows what I can do.
Attached Images
Just Bill
03-30-08, 04:14 PM
Most bath fans use a 4" duct, so it should work. Use rigid duct, less resistance. The usual rule of thumb for sizing is--1 1/2 times the sq ft of the room, in CFM. E.I., 50 sq ft should be 75CFM, or the next size you can find. The longer the run and elbows, the larger the volumn needs to be.
wendans
03-30-08, 04:44 PM
It is not the duct size that is the problem. It is the box size of the fan. I need it to be no bigger than 8" and have the box secured on the bottom of the box because of the pipe.
Just Bill
03-31-08, 04:52 AM
That could be a problem. Fans that small are that small don't do much, but moving some air is better than none. But try a search for 'bath fans', you may find one the fits and does a good job. Could the fan be remotely mounted, such as a Fantech unit??
wendans
03-31-08, 10:05 PM
I am going with a fantech PBW110. Much better than your ordinary exhaust and even quieter but it does come with a little price. The one thing is it will fit in my area.
Just Bill
04-01-08, 04:35 PM
They make an excellent product, but it is not cheap. In this case, I think you what you pay for.
Kobuchi
04-01-08, 05:09 PM
You can buy a much much cheaper in-line fan that fits inside 4" duct. It moves a piddly 50cfm, about the same as typical bath fan. Anyway, it's quieter and costs less than anything.
I've installed a few fans in line that were cobbled out of old range hoods. Dang powerful for a bathroom. But you have to cut and rivet sheet metal to set these up properly.
In a well insulated house, overdoing the exhaust causes negative air pressure in the whole house, which can make chimneys (and the combustion under them) blow in not out.
I've installed a few fans in line that were cobbled out of old range hoods. Dang powerful for a bathroom. But you have to cut and rivet sheet metal to set these up properly.
In a well insulated house, overdoing the exhaust causes negative air pressure in the whole house, which can make chimneys (and the combustion under them) blow in not out.