tips for DIY vent hood duct and roof cap install

[coffeefueled]

Has anyone installed the duct and roof exhaust cap for the range hood? It seems like it should be a doable DIY project. We installing a vent hood as part of our kitchen reno. It accepts 3 1/4 x 10 duct which we hope to run out the back, up the wall cavity, and through the roof. This will be our first time cutting through the roof or installing duct so any tips and suggestions are welcome.

Do you have a favorite exhaust cap? The local big box store has a broan model, but I've read online that the damper isn't very good.

[lthenderson]

I pretty much do this method from a This Old House episode for about any roof penetration that I have to make where it is a pipe boot or in this case a bathroom exhaust fan.

https://www.youtube.com/watch?v=PqrZWd_CQIE

I don't have a recommendation on brands but I tend to stay away from big box store models because they always tend to carry the cheapest (both price and quality) and instead order something online usually from the manufacturer, in this case the range hood. You pay more money but the quality is generally a lot better.

[KCM5]

I’m assuming installation on a wall rather than out the roof won’t work? I installed one out the wall, running it through the attic and it was really straightforward and I was less paranoid about leaks as it’s protected by the eaves. I’m a moderately handy woman and it took me about 6 hours to run the electricity, venting, and hang the new hood.

[Goldielocks]

I ran ours out the side wall, too.  It's about 9 ft up.  I was worried about cutting it through the top of the stud wall to get it into the attic.

[Papa bear]

Are you in a ranch or 2 story home? Does your range sit on an exterior wall?

Most construction is platform framed.  Which means that at every floor, there will be a double 2x4 that supports the floor, and then the attic above it.  If you go through that wall cavity, you will need to cut through these.  And ask me how I know, but they don’t always line up with the joists above!  So you may have to tear out drywall just to find out you can’t do it. 

Also, if it’s an exterior wall, you will have to remove the insulation to hardpipe up the walls.   Typically, you don’t mess with your insulation envelope of the home.  I don’t know about this exhaust pipe, but your hvac supply runs need to have a minimum Rvalue of insulation between the duct and outside wall. 

So, if it’s 1st floor kitchen, with 2nd floor and then attic, you will need to tear out the drywall on the wall through the entire run, tear out some of the ceiling drywall at each floor, cut out the double top plates at each floor, and hope to hell the joists and rafter ties sit right on the 1st floor studs, AND hope the 2nd floor wall studs sit right on that too.  Then, you still have the insulation to take out and replace according to local code. Then duct through your attic to get out of the roof not at your eaves. 

Now, if your house is balloon framed, you may have an easier time to run this ductwork.  BUT then you have a bigger issue overall because there wouldn’t be any fireblocking. 

All of this to say, holy hell what a pain in the ass! Go out the side wall!  Unless you designed and built the house to accommodate a vertical run up, stay far away unless you want a major rehab project.


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[coffeefueled]

The kitchen is in the original part of the house which is a one story cottage. Unfortunately the stove is on an internal wall and we can't run the vent in the ceiling joists and out a wall because of beam placement and the direction the joist runs. There's no good way to go out a wall with our kitchen layout. I hadn't thought about the top plates supporting the attic/roof, but yeah that makes running it in the wall make no sense. We decided to run the ducts on the kitchen side of the drywall, straight up into the attic, then 90 to avoid the roof peak/support structure and then out the roof.