i am updating my kitchen. i want to vent the hood outside. i will need to
vent up through the ceiling into the second floor crawl space. i do not
want to vent through the roof. i want to 90 back down and go through the
soffit.i would put a in-line damper and then vent right at the soffit.
could this be a reasonable application or should i avoid it.
i would appreciate any help on this matter.
Exhaust Fans - Installation Tips / Kitchen and Bath
Summary:
Install exhaust fans in the kitchen or bath by following instructions carefully. Most problems with kitchen exhaust fans or bathroom exhaust fans are derived by taking liberties with proper installation as given by the manufacturer. These tips will provide guidance to proper installation of your ventilation fans and avoidance of fire or other unhappy results.
Related Articles: Exhaust Fans, Sizing an Exhaust Fan, Exhaust Fan Manufacturers
Related Articles: Exhaust Fans, Sizing an Exhaust Fan, Exhaust Fan Manufacturers
Installation Tips
I know this sounds crazy, but be sure to carefully follow the instructions that come with your fan. The single biggest reason for problems with exhaust fan installations is failure to follow directions. It only takes five to 10 minutes to read instructions.
Be sure to use the recommended ductwork. Don't mix and match sizes, as you will affect the static pressure load on the fan!
For kitchen exhaust fans, be sure to use metal ductwork! Tape all joints with high quality duct tape. Fires are a real possibility.
Try to locate fans so that the duct run is as straight and short as possible. Remember, a 90 degree bend or elbow is often equivalent to 10 linear feet of duct run. Most fans have a limit to the total length of duct. Pay attention to this number!
Each exhaust fan has a discharge port where the exhaust air leaves the fan. This discharge port may be three, four, five or six inches in diameter. Do not, on your own accord, reduce the size of the duct between this port and your exterior termination cap.
I have found that it is often best to vent fans and dryers through the roof. I urge you to watch this video of mine to see how easy it is to install the correct vent-cap flashing on a roof. Have no fear - if done right you will have no leaks.
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ckane 15 Dec 2007, 20:50
AsktheBuilder 16 Dec 2007, 07:32
CKane,
I would never do this. The warm, moist air that often has oil in it will foul the soffit. It will also find its way into the attic space. Watch this video to see how easy it is to install the necessary roof cap: http://www.youtube.com/watch?v=gee3itzjOG0
Al D. 04 Feb 2008, 14:18
Based on the cold air that is pouring down from the hood into our kitchen
it seems that theroof cap for our kitchen exhaust hood does not have a
damper. The hood (Ventahood) itself has a damper, but it has big gaps that
let lots of air through.
My question is whether the roof cap should be replaced with one that has a damper, or is it better (and possible) to add a dammper to the duct as it exits the roof? If the former, do I need a special roof cap to match the pitch of the roof (10/12)? The cap I was looking at (Fantech RC8) seems to have the duct connection perpendicular to the flashing, but the duct coming out of the roof is vertical (plumb). Can the duct connector on the roof tilt to handle different roof pitches? I can't tell by looking at the pictures. Thanks!
AsktheBuilder 04 Feb 2008, 14:30
Al,
My Fantech roof vent has a 6-inch round collar that is part of the flashing. You would use adjustable fittings to transition from your vertical pipe to the flashing.
Al D. 04 Feb 2008, 16:33
Okay, I suspected that would be the case. Unfortunately there is no way to
get access to the duct below the roof to make the fittings without tearing
out drywall. I'm beginning to think that adding a damper within the
existing roof cap might be the simplest way to go. Any thoughts?
ABDUL 15 Mar 2008, 21:14
I am new house owner and live in two story house I planning to place
exhaust fan unfortunately we have bedroom just above the kitchen. Is it
possible to make hole in the wall on back of kitchen and place the exhaust
pipe for air. What do you recommend will that be any issues to structure of
the building.
AsktheBuilder 16 Mar 2008, 07:01
Abdul,
It is possible to go through the wall. The structural issues should be minor.
Amy 01 Apr 2008, 07:06
I have a 2 story house that has an existing exhaust fan that does not vent
to the outside. We would like to vent it to the outside but would have to
go downward into the crawl space under our house. Please advise how this
can be down and what products can be used to safely vent with 2 90 degree
turns.
tman 03 Apr 2008, 05:15
I am trying to install a JennAir Pro range hood with 6" round vertical
discharge, going up through the roof. My city code is asking for damper.
If I use 6" round dampers I find at my HW supply stores, installed directly
above the range hood I am getting tremendous noise from it with the vent on
even with low speed. The Jenn Air is definately >400cfm on max, might
be as high as 600-650cfm, has no damper itself. What is good solution.
Are there good roof mounted dampers I can order that will be okay? The exit
from roof (top of the duct) is about 10 feet above the range hood.
AsktheBuilder 04 Apr 2008, 04:52
Amy,
I cover this in all of my past columns about bath and dryer exhaust venting. Read all of my past columns please. View all comments |
