# Can I install a hood vent pipe with a 90° turn?



## Stephen S. (Nov 23, 2009)

The instruction only shows vertical venting (through the roof) or rear venting (through the wall). I don't know if venting through the roof is an option for me since the attic space on top of the kitchen is not quite accessible. However, the rear of my hood and range is not an exterior wall, so if venting through the wall is my only choice , I need to make a 90° turn on top of the hood then a 6 feet horizontal run such that the pipe can vent through the exterior wall ? Is that okay to do a turn?

Also, is it preferable (any advantage?) to have a roof vent than a wall vent?
Thank you.


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## CallMeChaz (Feb 6, 2010)

Stephen, 

The resistance to flow will be restricted a bit, but not enough to concern me. You are only running 6 feet after that, so the total resistance will be small. Just make the turn with the same size elbow as the vent pipe.

The only advantage I can see is you get a straight shot with the roof vent. But it's a lot harder to install, harder to seal. I see no problem.


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## Stephen S. (Nov 23, 2009)

I ended up installing the pipe up the roof, it's not too bad, the worst part is to crawl into the narrow, dark, dirty attic with blown in cellulose insulation twice to position and to connect the pipe to the vent. I ran a 6" pipe from the hood to the vent however I reduced it to 4" at the vent since I don't want to cut off too much roof, hope that it won't affect the venting ability much ...


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## CallMeChaz (Feb 6, 2010)

Steven,

Looks like an A1+ install! The 4" should do the trick, esp with a short, straight shot roof vent. A 6" would not really have been more difficult, esp with the neat job you did cutting through the roof and shingles. Thank you for posting a nice followup. That's really helpful to others who find this thread in the future.

Chaz


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## creamaster (May 11, 2008)

One thing I noticed is that you dont have the roof shingles overlapping on top of the flanges of the vent. If the picutre of the roof vent is the final assembly, there is risk of water seeping under the side flanges of the vent and getting into the hole and into your attic. You want to cut the shingels and have them over top of the vent flange on both sides and the top so as water rolls down the roof it simply travels over top of the shingels and down past teh vent never leaking into your vent hole you cut. Your caulking should go under these top shingels and caulked to your vent flanges.


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## CallMeChaz (Feb 6, 2010)

Woah, good catch! I was only looking at the uphill edge that appeared to be overlapped and tarred. Missed the first row of side shingles that should overlap the flashing. Gotta fix that. Good thing ya posted the pics, Steve.


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## Stephen S. (Nov 23, 2009)

Yeah taking another look at the finished picture again, I should have covered the sides with shingles as well and glue them to the vent.

Do I have to cover the sides with the shingles if I added an inch thick of Henry's roof cement under the perimeters of the square aluminum vent and under the shingle at the tiny overlap. I've put so much cement that taking if off now may damage the shingles?

Any other solution beside redo it ? Thank you.


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## CallMeChaz (Feb 6, 2010)

Hi Steve,

I don't want to step on creamaster as he caught this, but I'm at my 'puter so I'll toss in my 2 cents. Since this is a bit subjective at this point, other advice should be considered.

The nice thing about a correct install is that you don't have to monitor for problems--done right they are pretty secure for the life of your roof. That doesn't mean what you did won't work. You might have to check for signs of leaks in the attic 'till you are confident. You are correct, you may well tear up the shingles if you re-do. Here's my suggestion in order of best idea to least-best:

1) If you have any matching shingles, redo. If you tear a few up, replace them. You may be able to renail replacements, just don't bust the upper shingles trying. You can also glue the replacements in place with roof cement and they should be 99% as good as nailed. This should not require further maintenance.

2) If you opt not to redo, I would at least seal the edge of the side shingle with fibered roof cemnt "just in case". Perhaps lay a piece of fiberglass mesh in the joint like you do with drywall. Paint the joint with silver roof tar to reduce sun dry-out. This may require a yearly check to be sure the joint did not crack. Someone may know of a longer-life sealent that could take the UV from the sun better than tar that is compatible with shingles.

3) Don't do anything. Chances are if you sealed it well it won't leak. The sealant won't deteriorate because it is under the pipe flashing, protected from the sun's UV. This is a bit more risky if you get snow accumulated on the roof.

Chaz~


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## Stephen S. (Nov 23, 2009)

Lesson learned ... I'll choose option 2 + new shingles. Slip another piece of shingle under the top layer and overlap both sides of the vent and seal all the joints. That should work?

Thanks again Chaz.


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## CallMeChaz (Feb 6, 2010)

I was going to suggest that if you don't mind seeing an extra shingle sticking up. It's sorta' Idea 1-1/2 . That should be pretty much worry-free, as your sealant joints are protected from cracking in the sun.

Chaz


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