hakurai: OK, I'm home. I went up to the attic with the blower running at full speed. It's loud: a combination of a medium-low frequency hum from the motor, and a high pitched whine which I believe is from the fan airflow. I couldn't get a decent decibel rating: the blower is across on the unfinished side of the attic, and as someone who has fallen through the ceiling from the attic not once, but twice, in my career, I've learned what I am not capable of doing. At about 15 feet, it reads 57 db so I'm guessing at 3 or 4 feet it will read well into the 60's. It would, I suspect, be loud enough to annoy me, but I'm quite noise-sensitive (for example, I find the 600 cfm Vent a Hood that we have at the lake really annoys me, while many posters here think their units are very quiet). I think the bottom line is that if you're pulling 1200 cfm, it's going to be noisy no matter whether you use an internal blower, or an inline blower mounted just a few feet above your head. Still, if you're wedded to using the hood you have, then I think it would be much easier from a DIY standpoint to use the Fantech than to try and retrofit an internal blower "power pack" into your existing hood. That would require extensive metalworking, welding, etc I would suspect. So (and again, presuming you've gotten grease baffling addressed), I'd certainly consider that. The key is making sure you have a variable speed controller on the fan, which means that most of the time you'll be running at far less than maximum speed with a corresponding reduction in noise.

What you won't be missing after a while is the grease that will accumulate in the device that takes heat or cold (physicists need not point out the sloppiness of that phrasing) from the outgoing air and puts it back into the incoming air. Any effective and practical heat transfer device that I can think of will collect grease and dust in this application. I don't know how easy it would be to clean such a unit, but my guess is that they are not designed for this. Essentially, all kitchen ventilation puts effluent into the environment. This is nearly inevitable. The only question is what kind. Residential units and most commercial units pull grease, smoke, and water vapor from the kitchen and put it directly into the environment. The probably rare UV systems convert the effluent to simple molecules, but then the ozone they generate has to be vented, or somehow filtered out, perhaps by charcoal, generation of which has its own issues. So the only thing green about a kitchen is the paint, and the goal is to minimally risk fire while getting rid of the effluent. However, my view on this is somewhat speculative. A commercial HVAC company that deals in large HRV might have something that would be practical. Perhaps some need for commercial heat recovery has spawned a practical kitchen venting HRV. The Fantech has a washable filter. How long would it take for cooking grease to gag it? What of potential grease fires. And the specified cfm has to be reduced by all the other pressure losses, so you would likely need a larger unit anyway. kas

Hi all, I have some questions to ask current ARS users, due to the specific configuration of our stove area--it's not atypical, but it seems to be suboptimal for any of the ARS hoods' guidelines. Specifically, we plan to replace a hood/microwave hybrid that the previous owner (a flipper) installed over a 30" electric stove. The cooking space (i.e. the height of the area between the cooktop and the bottom of the hood/microwave) is 20", and the microwave itself is 15.5", and the microwave is mounted on a cabinet that's about 17" tall. However, since VAH's guideline suggests the cookspace should be 20-24" tall, installing the under-counter ARS hoods (PRAH6/SLAH6) directly under the cabinet would make the cooking space about 5.5" taller (29.5") than what's recommended. But the specs seem to imply the 30" wall-mount models use a 7' duct for all the filtration media, and our kitchen doesn't have that much clearance (the height between the bottom of the microwave to the ceiling is less than 5'). My questions for ARS owners are: Is the suction still acceptable if the clearance between the cooktop and the hood is 30" (instead of the 20"-24" recommended by the specs)? How likely an under-counter ARS (PRAH6/SLAH6) can be mounted on the wall? Can the wall-mounted ARS models be installed without a duct cover--and in that case, how long actually is the duct where the filtration takes place? Thanks for your answer in advance!

The Fantech duct silencer mentioned by kas does a great job of reducing noise from the remotely mounted (on roof, or in attic) motor/blower. You will not get away from the noise of air flow though the hood baffles/screen, but blower noise will be pretty much gone. If you are in a cold-weather area, or have gravity gas appliances (old fashioned water heater or furnace, for example) in the heated envelope or fireplaces, you need to understand the makeup air issue. The concern is that you don't want to back-draft your chimneys/exhaust ducts with a large fan in a well sealed house. Colder regions tend to have codes restricting the capacity of exhaust fans, above which you have to provide "make-up air" from outside. From a practical viewpoint, you can just open a window when using the fan at full blast, but regulations will not allow that. Here in San Jose, the two largest fans (hood, bathroom) combined cannot exceed 15CFM per 100 sq ft of house size without makeup air, if there are any gravity devices -- so I moved my water heater to a closet sealed from the house/vented to the outside, and my furnace to the vented attic.