Sorry to repeat our post, but we thought we might find a response here on the General Discussion board.
We're planning our kitchen renovation with emphasis on proper ventilation for the new gas cook top. We're planning on venting 4 feet up into our attic and then running 20 feet horizontally to our rear rooftop via 10 inch round duct.
We decided the fan would be mounted on our rooftop (exterior blower) but now question the advantage/disadvantage [instead] of using an In-Line fan somewhere in the unheated attic.
Without the benefit of past experience it seems logical to us that a fan inside the attic and free from the outdoor elements would make more sense in that a simple vent cap mounted on our roof top would be less intrusive than a complete blower system up there amongst our shingles. What is the professional opinion of going with an In-Line blower?
We've calculated the BTU output of the cook top and made the conversion to the CFM of the blower. We're also aware of the back drafting issues associated with the more powerful blower systems.
I believe you will get all the ventilation you need from an internal blower, besides the obvious element of not having to service a blower on your roof.
Check the duct sizing recommendations in the installation manuel, before just assumming that the big 10" duct is what you need. Oversized duct can reduce the velocity of air flow, and hinder the vent instead of helping. Even with the external blowers I have seen, they called for a 10" wall termination, but only an 8" duct run.
Last edited by troubleseeker; 11-25-2007 at 02:09 PM.