Kitchen Range Hood Wall Cap and Strong Winds
I am having a kitchen range hood and ducting installed shortly and am having some hiccups with finding an ideal wall cap.
I live in an area that has the potential for very strong winds and extremely brutal winters. I am having the duct work exit through the back wall of the house, which will require 1 elbow and about an 8′ duct run.
The kitchen range hood will have a gravity fed backdraft damper pre installed. The wall cap includes a gravity fed flap and an exterior guard. The manufacturer of the wall cap warned me that the wall cap flap is not the same as a backdraft damper and may not stay closed during very strong wind episodes, thereby allowing cold air in through the duct work. I thought about adding an additional backdraft damper in the duct line, near the wall cap, to serve as back up when the wall cap flap fails, but was told to be careful with setting up too many dampers (wall cap flap, in line backdraft damper, and range hood backdraft damper), as this may restrict airflow and build air resistance, which will reduce the effectiveness of the range hood.
Long story short, here are my questions:
1. Would adding a backdraft damper near the end of the duct line, by the wall cap, and eliminating the range hood backdraft damper be advisable? Having a wall cap flap and two downdraft dampers would be too much, no?
2. If installing a backdraft damper in the duct line close to the wall cap, would it still be necessary to insulate the duct work? Won’t the backdraft damper serve to prevent cold air from coming inside? Insulating would be overkill?
3. Should I not add any additional backdraft dampers and leave the wall cap flap (not the best in windy situations) and range hood backdraft damper and simply insulate? The backdraft damper pre installed in the range hood will do its job from preventing cold air from coming into the house? Only insulate to prevent duct condensation?
Thank you for your time.
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