How to Replace a Bathroom Exhaust Fan and Ductwork

This project shows how to remove a noisy economy bathroom vent fan and install a new Panasonic WhisperCeiling super quiet model FV-11VQ5 (Editor’s Note: this is a discontinued model, here’s a modern version). The old 3 inch vent duct is removed and new 4 inch flexible duct installed between the 2nd floor joists.

The old ceiling vent fan in the master bathroom was undersized and very noisy. The bathroom stayed steamy after a shower no matter how long the old fan was running. It was so loud I couldn’t hear the radio at a comfortable volume. It annoyed me so much I decided to replace it with a Panasonic WhisperCeiling bathroom ventilation fan.

Panasonic WhisperCeiling Vent Fans

I decided to expand my bathroom vent fan product search beyond the limited set of items available in the big box home improvement stores. The Panasonic WhisperCeiling bathroom vent fan product line is both popular and highly rated in user reviews on Amazon. I studied the product specifications and installation guide to convince myself it was the right product, then purchased the FV-11VQ5 model. The main features of the FV-11VQ5 vent fan are:

• < 0.3 Sones, which is the noise equivalent to a “very calm room”
• 110 Cubic Feet per Minute (CFM) air volume
• 4 inch diameter duct
• backdraft damper
• painted zinc galvanized steel housing for rust protection
• adjustable mounting brackets
• 21 watts power consumption
• Energy Star Qualified

Bathroom Ventilation Requirements

See the Bathroom Exhaust Fans – A Consumer Guide and Bathroom Ventilation Guidelines published by the Home Ventilating Institute for guidelines on properly sizing a bathroom vent fan in terms of Cubic Feet per Minute (CFM) based on the square footage of the bathroom.

The old economy bathroom fan was probably rated at 50 CFM isn’t enough air movement for the master bathroom. The new Panasonic FV-11VQ5 exhaust fan more than doubled the rated air movement capacity to 110 CFM which is about equal to the master bath floor space in square feet.

How to Replace a Bathroom Vent Fan and Ductwork

The steps for replacing a bathroom vent fan are:

1. Remove the old vent fan (see below).
2. Disconnect and remove the old 3 inch vent duct.
   No forethought was given by the architect and home builder about routing bathroom vent duct to the outdoors. My vent duct is far too long and crammed into the load bearing wall between the main house and garage. Replacing the old 3 inch uninsulated duct with new 4 inch insulated duct was a challenge.
3. Saw a mounting hole in the drywall ceiling between the joists to mount the Panasonic WhisperCeiling fan.
   I discovered the WhisperCeiling fan is designed to be installed either before the drywall is put up during home construction, or dropped in place from the attic. My problem is the a retrofit installation with access only from the interior room would not work because the fan box will not fit through the correctly sized ceiling mounting hole. I solved this by sawing a larger mounting hole in the drywall ceiling and installing a wood trim frame. This approach worked really well.
4. Install insulated 4 inch flexible vent duct from the bathroom to the outdoor vent.
5. Build a simple mounting frame of 2×2 lumber to support the bathroom fan between the ceiling joists.
6. Connect the NM-B 14/2 electrical wiring to the fan.
7. Remove the old 3 inch outdoor vent cap, cut a 4 inch hole in the exterior wall with a hole saw, connect the insulated vent duct and mount the vent cap.
8. Final 4 inch insulated duct connection and close the interior soffit with a plywood access panel.
9. Build a simple frame out of wood trim moulding, nail it to the ceiling and install the fan grill.

I doubt your situation will be as complex as mine but if you run into an bathroom fan installation problem you’ll know what to do.

The new Panasonic WhisperCeiling fan does an extremely good job and is so quiet it can’t be heard over normal conversation.

Project Update:

I more recently installed a Panasonic WhisperCeiling model FV-05VQ5 (Editor’s Note: this is a discontinued model, here’s a modern version) in the upstairs bathroom with new attic ductwork and soffit vent. See the new How to Install a Panasonic WhisperCeiling Bathroom Vent Fan for a revised installation method.

Remove the Old Bathroom Ventilation Fan

This is the original contractor grade bathroom ceiling vent fan:

Electrical Safety

Shutoff the electricity at the circuit breaker panel or fuse box to prevent shock, fire, burns and/or death.

The bathroom fan grille is held in place by two spring wires. Pull the grille down about 2 inches to expose the springs then squeeze the spring to pull it free of the motor plate.

Unplug the fan motor as highlighted in the yellow box:

Release the motor plate from the fan housing by inserting the tip of a screw driver into the slot beside the mounting tab (red arrow) and twist to disengage the steel tab:

Wiggle the motor plate out of the fan house to remove it:

This cheap ceiling fan has the centrifugal type blower wheel that operate by slinging the air outward. The flat wheel blades have poor aerodynamics which makes for inefficient and noisy operation:

Disconnect the Bathroom Vent Fan Electrical Wiring

The 120 volt AC fan wiring will be disconnected in the following steps.

Remember – the electricity should have been shutoff at the circuit breaker panel or fuse box as noted above. Verify the power is off by turning On the fan at wall switch and also with a voltage tester at the fan motor receptacle.

Pull down on the wiring cover to remove it and expose the fan wiring as shown:

After exposing the fan wiring, unscrew the two wire nuts to disconnect the black (hot) and white (neutral) wires. Use the tip of a screw driver to pry off the green ground wire tab.

Pry off the wire grommet with the tip of a screw driver to release it from the fan housing, then slip if off the wires.

Remove the Bathroom Vent Fan Housing

The bathroom ceiling fan may be nailed or stapled to the ceiling joists. Mine was stapled at the wings on either side of the fan housing. To figure out how it was fastened to the ceiling joist, I worked a flat head screw driver between the fan housing and 2×10 wood joist to locate the fasteners. It was easy enough to lever the staples out of the joist with the screw driver:

Prying off the mounting staple on the other side with a flat head screw driver:

Disconnect the Bathroom Vent Fan Duct

The bathroom ceiling fan is connected to 3 inch diameter galvanized duct pipe by metal foil HVAC tape. Cut or peel off the HVAC metal foil tape to disconnect the duct pipe from the fan housing:

The 3 inch duct pipe after disconnecting it from the ceiling fan housing. I’ve also unsnapped the black plastic duct connector from the fan housing:

Tip the fan over to slide the fan housing out of the drywall ceiling:

Here are the various parts of the old bathroom ceiling ventilation fan:

This project is continued in How to Replace a Bathroom Exhaust Fan and Ductwork – Part 2.

Take care,

Bob Jackson