Frequently asked questions regarding Exhaust Fans
1. 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 height over 8 feet, take the cubic feet of the room, (L x W x H), multiply that times 8. Take the sum and divide it by 60. Both calculations will give you the minimum recommended CFM.
2. What is CFM?
Cubic Feet Per Minute-Unit of measure for expressing volume (quantity) of air flow. For an exhaust fan it would be the quantity of air exhausted - the same quantity is brought into the room to replace what was exhausted.
3. What is a Sone?
A Sone is an internationally recognized unit of loudness. The Sone you see is the laboratory decibel readings translated into a number corresponding to the way people sense loudness. Sones are linear like inches. Double the sone is double the loudness. Another way to think of a Sone is that it is equivalent to the sound of a quiet refrigerator in a quiet kitchen.
4. Can I install a fan and/or fan-light over the bathtub or in a shower?
Products that have been Listed by Underwriters Laboratories Inc for use over a tub or shower may be used in this application. These products will be marked as "acceptable or suitable for use over a bathtub or shower when installed in a GFCI (Ground Fault Circuit Interrupter) protected branch circuit. Consult the catalog for product models rated for bathtub / shower" enclosures.
5. Can I install a heater over the bathtub or in a shower?
No. Broan-NuTone recommends against that. Besides, heaters are not UL (Underwriter's Laboratory) approved for installation over a bathtub or in a shower.
6. Can I cover the Bath fans with insulation in the attic?
Any fan unit can be covered with insulation. If you have a fan/light unit, it would have to have an IC rating. IC stands for insulation contact. Contact Technical Support for further information on approved fan/light units.
7. Where do I install a bath fan in the ceiling?
Usually an exhaust fan should be installed in, or closest to, the shower enclosure. Provide inlet air by an undercut door and/or air diffuser. Imagine a line between the inlet and the fan - position both to "sweep" the room
8. What would be some reasons for an exhaust fan not removing the moist air from the area?
Insufficient make up air into the room being exhausted; too small a device for the size room being exhausted; incorrect size of duct used to exhaust room; obstruction in the duct; roof or wall cap not opening correctly; incorrect position of product in room.
9. What accounts for "make up air" into a room?
Make up air is the air needed to replace air being exhausted by the fan. Inadequate make up air will result in poor performance of the product. For a bathroom installation, make up air is generally provided by a gap at the bottom of the bathroom door. A 1/2" gap between the bottom of the door and the floor or carpet is sufficient for most installations. Large CFM fans may require additional make up air.
10. Can I use a multi-port bath fan in one large bathroom?
Yes, this works the best for large rooms, because you would be able to install the ports over the areas where the ventilation is needed the most (source control). The size of the multi-port would be determined by the size of the room.
11. If I have three or more bathrooms, should I use a multi-port bath fan?
The multi-port bath fans are for continuous ventilation and will remove air from all the bathrooms at the same time. For proper ventilation, the room 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.
12. 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, which is what CFM is a measurement of.
13. Will a non duct exhaust fan remove the moisture in the room it is installed?
No. The product re-circulates air into the room being exhausted. An exhaust fan that could be ducted would be required to exhaust the humid air to the outside.
14. Can I install the bath fans in a wall?
Bath fans can be used in the wall - mount them as high as possible. 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.
15. Can I use a 3-inch duct pipe on a bath fan with a 4-inch duct connector?
This is not recommended. It will cause the fan to run harder and create excess noise. It will also reduce the performance of the fan.
16. Can I use 4-inch duct on a fan with a 3-inch connector?
Yes, if (insulated) flexible duct is used. Strap it tight with a long wire tie so it doesn't leak, and the result will be quieter.
17. 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 as straight as possible.
18. 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.
19. When would a roof or wall cap be used?
A roof or wall cap should always be used to: Terminate 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
20. 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 will damage the structure and insulation.
21. What type of exhaust fan is recommended for a sauna or hot tub area?
A high cfm rated device is normally recommended for this type of application.
22. Can all exhaust fans be put on a variable speed control switch?
This depends on the product model, as some motors are incapable of the varying speeds.
23. Why is there water dripping from my bathroom fan/range hood??
There could be two reasons for this issuse: Condesation 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.