Ductwork Through Floor Joists

This is typically the case for ducts that run through a dropped ceiling or soffit or between joists so long as the floor system sits on top of a conditioned basement or crawlspace.

Ductwork through floor joists. And wiring through a joist. Run hvac duct through composite lumber beams. The most common size duct used is 14 in. As we look closer here s what we see in this house.

Just be sure to get the sizing sorted out correctly ie a 12x12 duct cannot be replaced by a 3x48 duct same area as there s a lot more friction in the 3x48 but the correction factors for duct shape are surely. To minimize problems with ductwork. If the joists are in position and installed before the mvhr ductwork then very often this will create problems. Installing long sections rigid steel ducting through the gaps in the timber joists or steel posi joists very often won t be possible and the ducting would have to be cut into small sections to fit between the joists.

Still commonly used is the panned floor joist. What the installer did here was to screw a piece of sheet metal to the bottom of the joists and attach a duct to it to carry the air back to the hvac system. Most installers report they can get to a 100 sq. In this case it s big enough that there s even a joist running right through the middle.

Here are several ways to access ducts. If you need to cut through a joist firm up the floor as shown in fig. Area through this access hole. Position bathroom vent fans so the ducts can run parallel to the joists right up to where they exit the house.

Ducts should be able to run between studs in the wall and then turn into a joist bay the space between two joists. Attics can be problematic when insulation is located in the attic floor rather than in the rafter bays or better yet outside the roof sheathing. Is that a towel in there. The rise of wood i joists has challenged scl manufacturers to come up with a safe practical ways to permit larger.

You may be able to work with a wide shallow duct so you can have a broad not too deep soffit for the cross joist duct run. Using floor joists as return ducts by panning can cause leakage because negative pressure in the cavity will draw air from the outside into the cavity through the construction joints of the rim area at the end of the joist cavity.