Yes, this post is about running a dryer duct and rerouting HVAC vents. Before diving into the how-to, some context: when Monday’s post went up, David the framer was finishing the new laundry room by adding the fourth wall—the one that will include the door to the hallway.
He also framed the wall that will hold the frosted door to the current storage (future TV) room. I took the photo from this side to avoid the plastic sheeting that helps keep attic heat out.
Here’s a full view of the completed framing. I propped the door in place so you can see how far it will swing into the room. With an 8′ deep room, there’s plenty of clearance for the washer, dryer, and cabinetry.
This post isn’t really about framing, though—it’s about a few small but important tasks we needed to complete before drywall could start. They’re tedious, easy to overlook, and not glamorous, but necessary. Below are the three items we tackled, with photos and practical notes to help anyone facing a similar project.
First: the dryer vent. For safe and efficient dryer operation, the vent run should generally stay under 25 feet, and you should subtract about 5 feet for each 90-degree turn. Our old setup had too many turns and a length that likely exceeded recommendations, so improving the route was a priority.
Placing the dryer against the back wall of the new laundry room brought us much closer to the exterior wall, but our initial plan (Plan A) still required nearly as many turns to keep the pipe out of the way. Plan B proved better: routing the duct under the attic stairs resulted in a much shorter, straighter run. That required cutting a new hole in the exterior siding—a chore, but worth it to gain a safe, efficient vent path. I’ll explain why we chose to exit higher on the wall rather than under the stairs.
To create the under-stair passage, I used a Dremel Sawmax to cut the plywood top along the stair joist so it could be reattached later, then a reciprocating saw to remove a 4″ section of a 2×6 for the duct to rest in.
I planned to reuse the existing metal dryer vent pipe since it was in decent condition and I had many compatible pieces. I disassembled the sections, cleaned them with a long-bristled brush and a Shop Vac, and then reassembled them. For best practice, orient crimped ends in the direction of airflow and seal joints with metal-backed foil duct tape—not cloth duct tape.
I positioned the duct under the stairs and up to the exterior wall, securing it with steel hanger straps. One bottom section extended too far into the room, so I trimmed it with metal snips, leaving it slightly long until finish work is done. I covered sharp edges with painter’s tape to avoid cuts while working.
Next, I cut the new exterior hole for the vent. I started with a pilot hole from the inside to line up the duct location, then drilled the main hole from the outside using a 4-1/8″ hole saw so the opening would sit cleanly in the middle of a siding board. I only cut through the hardboard siding from outside and finished the hole from the inside to save time on the ladder.
Once the opening was complete, I installed a new exterior dryer vent hood similar to the old one. Sherry painted it to match the siding before I installed it, and I applied a ring of silicone caulk behind the hood for a weather-tight seal. A little sanding was necessary to fit the 4″ pipe through the 4-1/8″ hole, but the hood screwed in firmly once aligned.
We chose the higher placement for the new vent instead of an exit under the attic stairs because a low exit would sit just above a lower roofline and likely collect lint on the shingles. Placing it higher keeps lint away from the roof and aligns the new hood with the old one, so the exterior will look tidy once we remove and patch the old vent.
Inside, I trimmed the vent pipe flush and connected a semi-rigid duct, sealing joints with foil-faced duct tape and silicone caulk. Finally, I reattached the stair section I had removed so the structure is intact again. The dryer will need to be installed to fully finish, but the duct path is complete.
Briefly on the floor: the laundry room subfloor sat lower than the adjacent hardwoods. To make the tile finish flush with the hardwood, I planned for a 3/4″ subfloor layer, 1/2″ cement backer board for tile, and the tile plus thinset. I rented a small truck to transport the 4×8 sheets of OSB and other materials, trimmed the panels as needed, and glued and screwed them down to reduce future creaks.
Now back to HVAC. The new laundry room had no supply or return despite the main trunk being nearby. I researched and found helpful photo tutorials and a retail “Add-A-Vent” kit, but decided to buy the specific parts I needed individually. One useful product was a Speedi-Boot that makes installing a ceiling register between joists much simpler.
The part that made me nervous was cutting into the main HVAC trunk. After marking the collar location, I removed the insulation with a utility knife to expose the metal. To cut the opening in the metal trunk, I punctured the sheet with a flathead screwdriver and then used metal snips to cut the circular hole. The collar has tabs; I bent alternating tabs outward and inward so it could seat snugly in the trunk opening, then folded the inward tabs to hold it from the inside. I sealed the collar to the trunk with foil HVAC tape for an airtight connection.
I attached an insulated flexible duct from the collar up to the ceiling register, trimming the duct to length with a utility knife and cutting the internal wire coil with wire cutters. I secured the connections with a zip tie and foil tape, and used additional zip ties to hang the duct so it stayed smooth and kink-free to preserve airflow.
I left the temporary dust shield in the ceiling register until the room is ready for HVAC use, but I did test the A/C briefly and confirmed cool air flows as expected. With the dryer vent and HVAC connection complete, we cleared several critical items from the pre-drywall checklist, and drywall hanging has already begun.
It may not be the most glamorous update, but finishing these mechanical details means the room can progress to drywall and finishes. I’ll share drywall-hanging details once that stage is finished, which we hope to complete soon. For now, we’re pausing construction mode for a couple of days while we handle unrelated work, but it’s nice to see this room start to feel like a real space.