Newer-style bath fans, on the other hand, are so quiet you can hardly hear them running, and they cost very little to operate. It’s easier than you think to swap out that noisy, inefficient bath fan, especially if you choose one that’s designed to be installed without ripping out the bathroom ceiling.
Of the many replacement models to choose from, we picked the NuTone No. RN110 Ultra Pro Series because the fan can be installed from inside the bathroom. It’s not the quietest model available, but at 0.6 sones (about 25 decibels), it’s a huge improvement over the old 4-sone (about 60 decibels) fan we’re replacing. If you can locate a joist, cut drywall and handle basic electrical work, you can do the whole job in about two hours and save about $200 on the installation. You’ll need a stud finder, a drywall saw, a drill and screws, and aluminum duct tape.
There’s no such thing as a “one-size-fits-all” bath fan. For bathrooms up to 100 sq. ft., calculate the required cubic feet per minute (cfm) by multiplying the room’s length x width x height. Multiply that result by .13 and round up to the nearest 10. Example: 10 ft. wide x 9 ft. long x 9 ft. high x .13 = 105. Round up to 110 and buy a 110-cfm bath fan. For bathrooms larger than 100 sq. ft., simply add up the cfm requirements for each of these plumbing fixtures: toilet, 50 cfm; shower, 50 cfm; bathtub, 50 cfm; jetted tub, 100 cfm.
You’ll have to remove the power cable from the old unit and connect it to the new fan. This must be done with the power off. Don’t rely on turning off the fan switch; flip the breaker as well. Then double-check that the power is off with a voltage sniffer. If you’re not comfortable working with electricity, hire an electrician to remove and connect the wires.
Most bath fans are mounted to a ceiling joist with the duct running parallel to the joist. Start by locating the direction of your ceiling joists (Photo 1). Then locate the damper (you may have to remove the fan motor and blade from the housing). That’ll tell you where the duct lies in the ceiling. Mark the duct location. Then enlarge the opening (Photo 2).
With the opening now enlarged, you’ll have room to disconnect the old duct, electrical cable and old housing (Photo 3). Install and secure the new mounting frame (Photo 4). Connect the electrical cable to the new housing and snap the housing into the frame so the duct opening is facing the existing duct. Then connect the duct, damper and flange using aluminum duct tape (Photo 5). Finish the rough-in by connecting the power wires and ground to the electrical box provided (Photo 6).
Then simply slide the fan into the housing and add the muffler and grille (Photo 7). Turn on the power and test. Apply a bead of fire-resistant (intumescent) caulk around the fan housing and drywall to prevent moisture intrusion into the attic.
A new kit from Broan and NuTone lets you cut fan noise almost in half (meaning the fan is barely audible). Installing the new fan and motor only takes about 10 minutes, with no rewiring or duct work required. The kit works on most Broan, NuTone and Nautilus fans—most bath fans are one of these brands. The Bath Fan Upgrade Kit is simply a quieter replacement fan that fits in the existing housing, so there's no need to rip up the ceiling, and the new grille gives your fan a new look.
The more powerful motor in this quieter fan means the fan will do a better job of ventilating the room. Buy the kit (No. 690) on Broan's Web site (broan.com) or at most home centers. Everything you need is contained in the kit, including the wrench.
If you have a grille other than the two shown here, the upgrade kit won't work on your fan.