How quiet are external blowers?
I'm doing some research on what kind of range hood and blower I want in the house I'm remodeling. I'm going to have a 36" gas cooktop or rangetop. I haven't yet decided whether to open burners (probably BlueStar) or sealed (probably Wolf).
Here's a drawing of what the kitchen will probably look like. I have a straight shot of about 5-6' up from the hood to the roof -- the ceiling will be at 10' and then there's another 2' of joists etc. below a flat roof. (In the drawing I think I have the ceiling 1' too high.)
I haven't decided yet on what to do above the hood: chimney style, under-cabinet with upper cabinets or a soffit to hide the ducts, or whatever. Some of that depends on what kind of ductwork I need to keep it quiet. The kitchen is one end of a big great room, so I want to keep the noise level as low as possible.
What I think I need for a quiet system (based on reading posts here) is something like this:
- A 36" or 42" hood. 36" if possible so I have more upper cabinet space, but I can go to 42" if necessary.
- An external "updraft" blower on the flat roof. Something like what Greenheck makes. Their 095 or 099 models might even be small enough.
- Some ducting in between. Probably 10" diameter, and probably just straight up to the roof to minimize obstructions.
Does that sound like a reasonable plan? Do any of you have a feel for how noisy a system like this would be? I know external blowers are quieter, but with such a short duct run I'm worried that the blower noise will transmit down the duct fairly easily. What do you think?
If I need a silencer, does anyone have suggestions on where to put it based on the picture up above? I can't think of a way to do it with a chimney-style hood, since the diameter of the chimneys isn't big enough to hide one. And the 2' of space between the ceiling and roof isn't enough to hold the Fantech 10" silencers, which are around 35" long.
A couple ideas I had were to build a curb up on the roof that adds an extra foot below the fan, so the curb + ceiling area have room for the 3' silencer. Another option would be to put a soffit above the cabinets and hide the bottom end of the silencer in there. Do those plans sound sane?
If you have any suggestions or answers, or if you just think I'm insane and should start over, please let me know!