A new generation of efficient and quiet exhaust fans is now available at home centers and from heating, ventilation and air conditioning suppliers (under “Heating Equipment” in the Yellow Pages). The new fans are virtually silent. They're also much more powerful and use less energy than the older models. They can even be left on full time if you need continuous ventilation. (Most ordinary fan motors would burn out.) See “Shopping for a Quiet Fan,” below, for more details. In this article, we'll show you how to remove an old bath fan and install a new quiet one. In most cases you can do this in less than a day with little or no ceiling repair. While we're at it, we'll show you how to replace typical 3-in. uninsulated duct with much superior 4-in. insulated ductwork. This project involves electrical wiring, so call your local electrical inspector to find out if you need a permit. Installing a fan requires only elementary carpentry and electrical skills. You'll need basic hand tools, a power drill and a jigsaw.

The basic operations include hand sawing a small drywall opening, driving sheet metal screws into aluminum ductwork, cutting aluminum duct, climbing on the roof and sawing a larger roof vent opening, and disconnecting and reconnecting electrical wires. If you run into problems you can't handle, such as complicated electrical wiring, tight duct clearances, water damage at the roof vent cap or a steep roof pitch, don't hesitate to call a licensed electrician. You'll have to go into your attic and walk on your roof, so play it safe. Wear a long-sleeve shirt, long pants, boots, a hat and a dust mask to protect yourself from dust and insulation in the attic. While on the roof, use roof brackets, roof cleats or a safety harness for secure footing and fall protection. And if your roof is too steep or you don't feel confident up there, hire a pro for this part. The bath fan we're replacing is fairly typical. It's located in a ceiling with an accessible unfinished attic above. The fan is properly wired and ducted with 3-in. uninsulated ductwork to the roof.

If your old fan unit has additional features like a light or heater that operates off a second switch, your electrical wiring will be more complex. Outdoor Teak Table TopsIf the rewiring confuses you, consult a licensed electrician to work out the details. Custom Framed Mirrors NycIf you have a second floor above the fan, measure the height of the space available. Moving Companies BruneiThe new, quieter fans are taller than the old ones, at least 7-1/2 in. tall. While it should fit into typical floor joist space, check the fan dimensions to make sure. If you don't have an attic above, as we show, you'll have to do the entire installation from below. This means you'll have to cut open the ceiling a bit (and patch it later!) to get the fan in and run ductwork to a wall vent cap.

The connections will be the same as we show in the photo series. However, changing to a larger wall vent cap can be more complex if you have brick, stucco or vinyl siding rather than wood. If you're unsure how to proceed, check with a siding specialist for advice.Flexible duct is available in a variety of sizes that fit most bath fans. Bathroom fans, also called exhaust fans, prevent moisture damage and mold by forcing air through a duct to the outside of a building. In single story homes, the duct routes through the attic and connects to a roof jack. In homes and buildings with upper floors, it’s necessary to route duct from a first floor bathroom fan to an outside wall. Consult the local building department regarding specifications for the size of a fan motor needed for a particular length of vent duct. Install the fan according the manufacturer’s instructions and obtain flexible duct to vent a first floor bathroom. Determine which side of the building to route the vent duct from the exhaust fan.

Bathroom fans install between two ceiling joists and have ports at each side for connecting the duct. If possible, route the duct to a side or back of the building instead of the front. Wear safety glasses and a dust mask. Remove a 16-inch wide strip of the drywall or plaster ceiling between the fan and the outside wall. Cut the strip with a reciprocating saw fitted with a drywall or plaster cutting blade. Remove and save any insulation from the space between the ceiling joists. Measure the diameter of the flexible duct. Cut a hole 1/2 inch larger in diameter at the outside wall using the appropriate tools for wood siding, stucco or masonry. Apply a generous amount of construction adhesive on the back of the exhaust fan flashing. Fit the flashing into place at the outside wall. Fit one end of the flexible duct onto the inner, circular end of the vent flashing. Secure the connection with a nylon tie and two wraps of duct tape. Route the flexible duct from the flashing to the corresponding port on the side of the bathroom fan.

If you use more than one length of duct, connect the sections with wraps of duct tape. Cut the last section of duct to length with sheet metal scissors. Connect it at the fan with a nylon tie and duct tape. Set up a power or cordless drill with a screw-tip attachment. Support the duct in the space between the ceiling joists with duct straps every 36 inches. Attach the ends of the straps to the corresponding sides of the joists with 1¼-inch drywall screws. Reinstall any saved insulation in the space between the joists before patching the drywall or plaster. Things You Will Need Safety glasses Dust mask Reciprocating saw with drywall or plaster cutting blade Vent flashing Construction adhesive Flexible duct Nylon ties Duct tape Sheet metal scissors Duct straps Power or cordless drill with screw-tip attachment 1 1/4-inch drywall screws Tip Warning References Lowe’s: Installing a Bathroom Exhaust FanInspectapedia: Bathroom Ventilation Fan Installation and Improvement Guide Photo Credits Zedcor Wholly Owned/PhotoObjects.net/Getty Images Suggest a Correction