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Our house has 3 bathrooms: 2 have no exhaust fans, the other has an exhaust fan that has long tubing in the attic and vents out the side of the house rather than the roof.

We will be adding in 2 fans and upgrading the 3rd. Before electrical upgrades (including fans) we are replacing the roof. The plan is to have the roofers put in the 3 roof vents, and then later have electricians install the exhaust fans and connect the ductwork to the vents.

My question is, how exact do we need to be with the roofers installing the (currently nonexistent) vents? I can guide them to where the bathrooms are, but will it be an issue if the electrician goes to connect the duct and it isn’t a perfect straight shot up through the attic?

Dave
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Roof vents are almost never in alignment with the fans. They're connected with flexible duct or adjustable elbows. There has to be a bend coming out of the fan anyway, so it's not important if there's a tilt to the duct as it rises.

Position your vents so they clear the roof framing and don't interfere with drainage or sit where deep snow tends to accumulate. Also take aesthetics into consideration. A few extra feet of duct on a relatively short run is worth not having a bunch of hardware on the front plane of your roof.

isherwood
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If the attic allows, the best placement (roofing-wise) is to run the ducts so the vents go out the peak of the roof. That makes the job of the flashing around the vents much easier, as there's no water, snow, or ice running or sliding down the slope of the roof to the vent location, wearing on the flashing. Venting-wise, short and straight out the roof is better. Big-picture, you make trade-offs between the two depending on how much extra vent going to the peak will take.

Whether your electrician considers connecting fan ducts to be in their scope of work may vary, and whether you want to pay electrician rates for doing ductwork may also vary. If not doing that yourself you still might get a better job at a better price from someone who's job is installing ductwork, not running wires.

Offsetting a duct is easy, from "trivially" if using flex duct (which has the downside of restricting flow .vs. rigid duct) and "nearly as trivially" using rigid duct elbows which can be rotated to make various angles.

Ecnerwal
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