Bathroom Fans Questions and answers
How do I calculate the size fan for my bathroom?
- For an 8 foot ceiling, take the square footage of the room, multiply it by 1.1.
- For any ceiling over 8 feet, take the height of the ceiling and multiply by .1375. Take this figure and multiply by the square footage of the room. This will equal the recommended CFM’s. (Example- 10′ x 12′ room with 10′ ceilings. 10′ x .1375 =1.37 x 120 square feet = 164 CFM’s.)
- Both calculations will give you the minimum recommended CFM.
If I have three or more bathrooms, should I use a multi-port bath fan?
The multi-port bath fans will remove air from all the bathrooms at the same time. For proper ventilation, the fan should be sized properly. (Sq.Ft. x 1.1) There are a number of factors (size of the rooms, length of the ductwork, etc.) that would determine if this application would be better than using individual fans. When used with insulated ducting, this can be a very quiet installation.
Does a duct-free bath fan have a CFM rating?
No, a duct-free fan is not a ventilating device. It does not remove air from the room.
Will a duct-free exhaust fan remove the moisture in the room it is installed?
No. The product re-circulates air into the room being exhausted. A ducted exhaust fan that is ducted to the outside would be required to remove the humid air to the outside.
Can I install the bath fans in a wall?
Bath fans can be used in the wall. Mount the fan as high as possible on the wall. When wall thickness is an issue, use “thinner” fans. You can contact Technical Support for other fans that may be used in wall applications. Any fan with a light should not be installed in a wall.
Can I use a 3-inch duct pipe on a bath fan with a 4-inch duct connector?
No. It will reduce the performance of the fan and create excess noise.
Can I use 4-inch duct on a fan with a 3-inch connector?
Yes. A 3 to 4 inch adapter will be required to make this transition.
What type of duct is recommended, galvanized metal or flexible plastic?
It is recommended, where possible, to use rigid galvanized duct. It has less resistance to air flow and allows the fan to operate much more efficiently. If flexible plastic is used, insure the duct is stretched out and as straight as possible.
Can I use a utility fan in a bathroom?
Utility fans are not recommended for bathrooms. Broan-NuTone offers a complete line of bathroom fans to meet any style or specification.
When and why would a roof or wall cap be used?
A roof or wall cap should always be used. It will provide:
- Termination for the end of the duct run in the wall or on the roof
- Protection from the elements (water, wind) coming inside
- Protection from animals invading the opening
Can I exhaust my fan into my attic instead of out the roof or wall?
No. You should never exhaust air into spaces within walls, ceilings, attics, crawl spaces or garages. The humidity may damage the structure and insulation.
What type of exhaust fan is recommended for hot tub area?
A high cfm rated device is normally recommended for this type of application.
Can all exhaust fans be put on a variable speed control switch?
This depends on the product model, as some motors are not designed for use with speed controls.
Why is there water dripping from my bathroom fan/range hood?
There could be two reasons for this issue:
- Condensation can form in the duct pipe when it is exposed to a cold attic environment. The recommended solution is to wrap the duct pipe with insulation. The duct pipe should also have a damper at the discharge end of the pipe.
- During very cold weather, frost can form on the Vent’s roof cap. As warm air rises inside the duct, some of the frost may melt and drip back down the duct pipe. In certain very cold climates, some minor leaks and drips may be impossible to stop.
