How to Replace a Bathroom Exhaust Fan and Ductwork – Part 5

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The new bathroom ventilation fan is designed to be installed from above the ceiling (e.g. from the attic) but this isn’t possible when replacing a vent fan in the drywall ceiling between the first and second floors. To solve the “old work” installation challenge, a simple wood frame is built to mount the bathroom ventilation between the ceiling joists. This project is continued from How to Replace a Bathroom Exhaust Fan and Ductwork – Part 4.

Bathroom Ventilation Fan Ceiling Mounting Frame

The Panasonic WhisperCeiling FV-11VQ5 ventilation fan installation instructions assumes the fan will mounted to the joists before the drywall is installed, or you have attic access to mount the fan between two joists using the supplied telescoping mounting brackets. Neither approach would work for me because the fan is being installed between the space between 1st and 2nd floors in an “old work” situation. I only have access to the hole in the bathroom ceiling to mount the fan and needed a new mounting method.

Update: Panasonic has since introduced the WhisperFit EZ product line for old work/retrofit applications such as this. The WhisperFit EZ includes a Fast-Z Flex metal mounting bracket which avoids making a wood mounting frame. See How to Install a Panasonic WhisperFit EZ Bathroom Fan for details.

The old work mounting method I chose was to make a mounting frame out of 2×2 inch wood balusters left over from my porch deck rail project, Simpson Strong-Tie A21Z Z-Max steel angles and wood screws:

Panasonic WhisperCeiling Fan FV-11VQ5 Installation: Ceiling Mounting Frame

Panasonic WhisperCeiling Fan FV-11VQ5 Installation: Ceiling Mounting Frame

The two side braces with the steel angles will be fastened between the 2×10 inch joists with wood screws. The cross brace (right side in the above photo) is fastened with 3 inch wood screws to the side braces. The fan flange will be fastened with screws on two sides: 1) to the 2×10 joist and 2) to the cross brace.

The cross brace is approx. 15 inches long to allow clearance for the junction box and duct adapter. This dimension is not critical so long as the 2×2 brace does not interfere with the air duct connection. The two cross braces are 14-1/2 inches long which is the distance between the faces of 2×10 joists on 16 inch centers. Some fitting and trimming was necessary because my joists were plus/minus 1/16 to 1/8 inch from being exactly 14-1/2 between the joist faces.

Notice how the left side brace and bottom cross brace in the next photo overlap the mounting flange of the fan housing for fastening the fan with screws to the 2×2 frame:

Panasonic WhisperCeiling Fan FV-11VQ5: Wood Mounting Frame

Panasonic WhisperCeiling Fan FV-11VQ5: Wood Mounting Frame

Below is the assembled Panasonic ventilation fan mounting frame. The FV-11VQ5 fan housing is 10-1/4 inches square; I set the cross brace at 10-7/16 inches to allow 3/16 inch for clearance between the frame and fan housing.

Take care to drill 1/8 inch pilot holes for strain relief such that the wood screws don’t crack the 2×2 framing:

Install a Bathroom Ventilation Fan: Ceiling Joist Wood Mounting Frame

Install a Bathroom Ventilation Fan: Ceiling Joist Wood Mounting Frame

Install Vent Fan Mounting Frame between the Joists

The side brace that is on the back of the fan (i.e. opposite side from the duct adapter) is removed from the mounting frame and fastened with wood screws between the two 2×10 inch joists. Note that this brace is aligned with the edge of the mounting hole in the drywall ceiling. This simple task of setting four wood screws (two screws in each end for the angle brackets) took me at least 15 minutes due to the awkward and cramped workspace. Tip: Start the wood screw by tapping it with a hammer so it sticks in the joist, then set it the drill/driver. Those wood joists are hard!

Panasonic WhisperCeiling Fan FV-11VQ5 Installation: 2x2 Cross Brace

Panasonic WhisperCeiling Fan FV-11VQ5 Installation: 2×2 Cross Brace

Now you can see why the back cross brace was installed first because the assembled frame would not fit through the drywall ceiling mounting hole! The L shaped assembly here fits easily through the vent fan mounting hole:

Panasonic WhisperCeiling Fan FV-11VQ5 Installation: 2x2 Mounting Frame

Panasonic WhisperCeiling Fan FV-11VQ5 Installation: 2×2 Mounting Frame

Fasten the L frame section (above photo) to the previously installed cross brace with a 3 inch wood screw. The pre-drilled pilot hole from the fully assembled mounting frame put together on the work bench is a essential for driving in the 3 inch wood screw because you’re working blind and can’t see around to the other side of the frame:

Bathroom Vent Fan Ceiling Frame: Fasten the L Section to the Rear Cross Brace

Bathroom Vent Fan Ceiling Frame: Fasten the L Section to the Rear Cross Brace

Fasten the angle brackets on the frame L shaped section to the 2×10 joists on both sides. Notice the clearance from the edge of the drywall ceiling to the cross brace to allow space for the fan junction box and duct adapter. I’ve pushed the insulated flexible duct back out of the way:

Bathroom Vent Fan: Installed Ceiling Mounting Frame

Bathroom Vent Fan: Installed Ceiling Mounting Frame

Panasonic WhisperCeiling Fan Electrical Wiring

Turn off the electricity to the fan circuit at the circuit breaker panel to prevent electrical shock and/or death. Verify the power is Off with a voltage detector. I prefer a non-contact voltage detector for convenience.

The Panasonic vent fan FV-11VQ5 electrical wiring is simple. I used the following items to hookup the fan to the house wiring:

  • An approx. 2-1/2 feet length of 3/8 diameter aluminum flexible conduit.
    The purpose of the flexible conduit is to protect the NM-B 14/2 electrical cable from rubbing against the fan housing, potentially wearing through the insulation.
  • Red plastic No. 0 MM Bushing.
    The MM bushing protects the NM-B 14/2 cable from the sharp edge of the flexible conduit.
  • Raco 1/2 inch REDI-LOC Connector to secure the aluminum conduit to the fan junction box.

You can find MM Bushings and REDI-LOC Connectors at the home improvement store in the electrical supply section.

Panasonic WhisperCeiling Fan FV-11VQ5: Electrical Wiring Hookup

Panasonic WhisperCeiling Fan FV-11VQ5: Electrical Wiring Hookup

Install the Panasonic exhaust fan wiring by:

  • Tape the ground wire, black (hot) and white (neutral) ends of the NM-B 14/2 house wiring together so the wires don’t snag on the ribs of the aluminum flex conduit.
  • Insert a red plastic No. 0 MM Bushing into the aluminum flex conduit.
  • Push the NM-B 14/2 electrical cable into the flex conduit as shown.
    Straighten any bends in the wire so it pushes more easily through the flex conduit.
  • Push the NM-B 14/2 through the flex conduit until the outer insulation jacket extends just past the other end of the flex conduit with 6 inches of wires exposed. See How to Replace a Bathroom Exhaust Fan and Ductwork – Part 6 for additional wiring details.
Bathroom Ventilation Fan Wiring: NM-B Armored Cable Bushing

Bathroom Ventilation Fan Wiring: NM-B Armored Cable Bushing

Test Fit the Bathroom Exhaust Fan in the Ceiling Opening

Since I was working by myself on a step ladder to reach the drywall ceiling, I needed a way to hold the Panasonic WhisperCeiling vent fan while connecting the wiring and ductwork. My solution was to set a pan head wood screw high on the joist and wrap a 3 feet length of general purpose wire around the screw (see the following photo). The free end of the wire will be wrapped around the fan mounting bracket behind the junction box to hang the fan below the ceiling while I’m working.

Houston, we have a problem!” – When I tried to set the Panasonic WhisperCeiling exhaust fan into the 10-7/16 inch square mounting hole in the drywall ceiling the fan wouldn’t fit! The problem is the duct adapter is fairly large and there was insufficient clearance to slip the fan into the ceiling. My only choice was to extend the ceiling mounting hole to 13 inches by sawing another 2 inches of drywall ceiling on the duct adapter side of the mounting hole.

Update: It’s not necessary to cut a larger mounting hole as I later learned when installing a Panasonic WhisperCeiling model FV-05VQ5 in the 2nd floor bathroom. (The FV-05VQ5 dimensions are identical to the FV-11VQ5 fan.)

Just remove the duct adapter assembly from the fan body, connect the wiring and vent duct, then insert the fan body into the ceiling after duct adapter because the two parts will align and snap together. The revised installation method greatly simplifies things.

The new dimensions are 10-7/16 inches x 13 inches as shown:

Panasonic WhisperCeiling Vent Fan Installation: Modified Ceiling Mounting Hole

Panasonic WhisperCeiling Vent Fan Installation: Modified Ceiling Mounting Hole

The Panasonic bathroom exhaust fan now fits in the drywall ceiling. I’ve drawn outlines for the ceiling joist and 2×2 mounting frame on the photo for clarity:

Panasonic WhisperCeiling Exhaust Fan Installation: Ceiling Mount

Panasonic WhisperCeiling Exhaust Fan Installation: Ceiling Mount

You’re probably asking “What about that big ugly gap in the bathroom ceiling drywall?!” I pondered that question and came up with a really nice solution: Build a decorative wood trim moulding to cover the drywall ceiling gap as explained in How to Replace a Bathroom Exhaust Fan and Ductwork – Part 9 of this series. It looks really nice.

This project is continued in How to Replace a Bathroom Exhaust Fan and Ductwork – Part 6.

Thanks for reading,

Bob Jackson

Copyright © 2018   Reproduction strictly prohibited.


  1. JoJo June 26, 2014 at 5:09 pm - Reply

    there is not hole in my new ventiline exhaust fan to connect the duct so it can run out throuh my roof, my old fan had the opening for the duct to connect it to?? what the heck? Ventline 50 CFM Bathroom Ceiling Exhaust Fan

  2. Alex August 7, 2015 at 12:50 pm - Reply

    Awesome write-up.

    And I’m going to steal the idea of the wood frame to fix a few of my A/C vents that were poorly mounted and screwed to the drywall which is crumbling and not allowing the vents to be fastened back.

  3. Paul September 25, 2015 at 4:49 pm - Reply

    Very well done. I am in the process of doing this exact project with Panasonic fan without access to above and all work has got to be done from below. I openened sheetrock approximately an extra foot or so to allow more access to opening. Can I use 1×2 instead of 2×2? Also from your pictures it looks like fan is screwed to drywall with 1×2 under sheetrock, slipped under 2×8 joist. Will there be any problem? Thanks for all your information

  4. PAUL September 27, 2015 at 5:26 pm - Reply

    Thanks for the reply Bob. A couple of more questions. I presently have a joist that is 1×8. with nothing but roof above. I am assuming the the housing will fit but presenty have a soffit vent 6 feet away and I am thinking of opening for a roof vent. What do you think.?
    The soffit vent has been connected for 5 years.
    Also thinking of bending nails that have come through from above sheathing protruding 1/4 below sheathing.(afraid they will hit housing.
    What is best way to extendflexible venting approximtely a foot.
    Bob, great info. Thank you.

    • Bob Jackson September 28, 2015 at 10:10 pm - Reply

      I’d avoid roof penetrations due to the increased possibility of a leak. Venting to the soffit is so much simpler. Set some plywood on the attic joist so you can lie down and reach the soffit if you have a low pitch roof.

      Roofing nails aren’t a problem if you’re careful and push the flex duct down to the soffit, which is what I did in How to Install a Soffit Vent and Ductwork for a Bathroom Vent Fan. You can cut off the nails with a small pair of bolt or heavy wire cutters.

      To splice duct, buy a 6 inch long sheet metal coupling the same diameter of the flex duct inner core. Slip band clamps over the flex duct, then onto the sheet metal coupling. Seal the flex duct to the coupling with metal foil HVAC tape then tighten the band clamps over each end of flex duct. Pull the insulation together to cover the splice and seal with HVAC tape. The materials are shown in the Soffit Vent project at the previous above.


  5. Paul October 1, 2015 at 12:48 pm - Reply

    Hi Bob,
    Thank you for your response. I am ready to install fan but realized I have 1×2 strapping that sheetrock adheres to under 1×8 joists. Can I just set wood frame to joist similar to strapping and fasten frame of fan to a fan box like the one you show in pictures. fit under sheetrock and fasten with drywall screws and then slip up fan?Thanks for all your help and reponses

    • Bob Jackson October 2, 2015 at 9:30 am - Reply

      How old is your home? 1×8 ceiling joists are a bit unusual. The 1×2 strapping is to provide a wider surfacing for fastening the drywall.

      A 1×8 joist is 3/4 inches wide. The 1×2 is 1-1/2 inches wide. Given the 1×2 is nailed against the bottom of the joist (like an inverted T) that means there’s a 3/8 inch wide step or lip. I recommend cutting a rectangular plate say 6 inches wide by 4 inches high from 3/8 inch thick plywood. Set the plywood plate on top of the 1×2 lip against the 1×8 joist, this way you’ll have a flush surface to fasten the fan mount wood frame with the Simpson Strong-Tie angles and screws. Set the longer side of the angle against the plywood plate & joist face so the screws will go into the 1×8 joist.

  6. Paul October 2, 2015 at 3:30 pm - Reply

    Sorry I meant 2×8. My mistake. I was thinking I could use(screw) 1×2’s into 2×8 joists where the gap is between drywall and 2×8 joist then screw fan into in 1×2 instead of Simpson angles. Will this be a problem? Thank you again.

    • Bob Jackson October 2, 2015 at 5:06 pm - Reply

      I’ve got the picture now. The 1×2’s are set across (90 degrees) to the 2×8 joists. If the ceiling joists are spaced 24 inches or less apart your plan should be fine. The fan isn’t heavy and with a combination of drywall and 1×2’s it should carry the load without sagging.

  7. Paul October 3, 2015 at 2:46 pm - Reply

    Thank you

  8. Donnie Thompson April 14, 2016 at 5:31 pm - Reply

    Good instructions but there is a much easier and efficient way. I can replace one of these Panasonics at an existing fan location in less than 30 minutes without opening up the sheetrock other than the size of the fan. If any extra materials are required then I occaissionaly will need a 12″ long piece of 1×2 or 1×3.

  9. Phil Crump August 2, 2016 at 2:34 pm - Reply

    I have installed a Panasonic Whisper in my bathroom as well. I am building a new house, SIP construction and wanted your thoughts on connecting the bath fan and oven fan into a single exhaust just before exiting the house. would prefer not to have anymore holes in the exterior walls then I have to. the bath fan is 3 feet from the exterior wall and the stove vent is just under 7 feet. straight line no bends or turns other then the 90 for the kitchen vent though a cabinet. I was looking at a Y pipe to connect the two just be for the wall.
    Thanks for your time.

    • Bob Jackson August 2, 2016 at 7:05 pm - Reply

      Before getting into the building code requirements, consider the consequences of connecting the bathroom and kitchen fan exhaust ducts to the same outdoor vent: Do you want bathroom odors in the kitchen? Or vice versa?

      The two fan units will have a backdraft dampers and the outdoor vent should have damper. However dampers are not 100% airtight, may not always close completely and air/odors can leak into the kitchen or bathroom if running one fan but not the other. On windy days the outdoor & indoor dampers will open & close due to changes in air pressure resulting in leakage allowing odors to travel between the kitchen and bathroom.

      It would also be a Building Code violation because the kitchen exhaust duct “shall be independent of all other systems”:


      M1503.1 General.
      Range hoods shall discharge to the outdoors through a duct. The duct serving the
      hood shall have a smooth interior surface, shall be air tight, shall be equipped
      with a back-draft damper and shall be independent of all other exhaust systems.”


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