This project is continued from Part 7.

Bathroom Exhaust Fan Ductwork Connection

With the other end of the flexible duct now connected to the outside vent cap, I’m ready to make the final 4 inch vent duct connection inside the interior soffit in the garage. To connect the bathroom fan vent duct in the interior soffit to the duct coming down from the bathroom ceiling:

1. Place the two worm gear band clamps over the two ends of the duct.
   I used a piece of duct tape to temporarily hold the upper clamp out of the way.
2. Slide lower section of flex duct over the 4 inch duct connector until it meets the connector center rib.
3. Wrap two layers of aluminum foil HVAC tape over the lower duct to secure and seal it to the duct connector.
4. Tighten the two band clamps over the ends of the flexible duct on the duct connector.

Interior Soffit: 4 Inch Bathroom Exhaust Fan Duct Installation

Here’s the flex duct connection after installing the HVAC tape and worm gear band clamps. Try to keep the bends wide and gentle as possible to minimize air flow friction losses.

4 Inch Bathroom Exhaust Fan Ductwork Installation: HVAC Tape and Band Clamps

The outer insulation jacket is pulled over the flex duct inner core to insulate it to prevent condensation of the warm moist bathroom air in the soffit in the unheated garage during cold weather. Condensation inside the vent duct could cause water to pool and promote growth of mold or mildew, or even a water leak over time. (Recall that the blue painter’s tape lines the edge of the drywall hole to keep down dust.)

Interior Soffit: Bathroom Exhaust Fan Vent Duct Installation

The new run of 4 inch insulated flexible duct from the Panasonic WhisperCeiling™ FV-11VQ5 exhaust fan installed in the master bathroom ceiling to the outdoors is now complete!

Drywall Access Panel Installation

I’ll install a plywood access panel to cover up the access port I cut on interior soffit in the garage, using the same technique as before. The 2×4 horizontal framing members at the top and bottom of the access port are conveniently located so that I mount the plywood access panel, but I need to install 2×4 framing on the sides of the drywall access port.

I measured and cut two pieces of 2×4 leftover from a previous project that just happened to be painted white. Pilot holes for 3 inch wood screws were drilled and the wood screws partially driven in to make it easier to mount the pieces to the top and bottom soffit framing.

Drywall Access Panel Installation: 2×4 Framing

The 2×4 side framing members are set flush with the edge of the drywall access port and attached to the interior soffit framing with the 3 inch wood screws:

Drywall Access Panel 2×4 Framing Installation

I measured and cut a 3/8 inch plywood access panel cover that is an 2 inches wider and 2 inches taller than the hole in the interior soffit so there is a 1 inch overlap over the drywall on all sides of the hole. The back of the access panel is lined with self-stick PVC foam camper mounting tape to keep out dust, bugs and prevent drafts.

Interior Soffit: Drywall Access Panel Installation

The drywall access panel is mounted to the 2×4 framing with 1-1/4 inch pan head wood screws set 5/8 inch from the panel edges. Use a bubble level to mount the panel plumb. I didn’t set the two wood screws in the center of the left and right side (see small red marks in the photo) because the plywood had a slight outward horizontal bow that caused the sides to pull tight against the soffit drywall. If I later notice a gap on the sides, I’ll add the two side screws.

Take care to set the wood screws just tight enough to evenly compress, but not crush the foam camper tape. The foam tape needs to remain “spongy” to expand and make an air tight seal.

Drywall Access Panel Installed on the Interior Soffit

For perspective, this is the interior soffit in the garage after the drywall access panel has been painted white to match:

Interior Soffit and Drywall Access Panel

And the new 4 inch vent cap for the Panasonic WhisperCeiling bathroom exhaust fan after caulking and painting to match the stucco:

4 Inch Bathroom Exhaust Fan Vent Cap

This project is continued in Part 9.

Thanks for reading,

Bob Jackson

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