Mine is from builder. It is one of Thermolec air heaters ( http://www.thermolec.com/en/productView.aspx?type=product&id=77) plus a separate current triggered flapper. The heater tries to heat the air to 15 C (PWM), activated by the air flow. It is a passive one and connects to the air return of the furnace via a 10 inch duct. It is not as sophisticated and highly performed as Kas's.

Differential means the difference between the outside temperature and the temperature you want the MUA to be (warmer or colder than outside). CFM means actual hood CFM, and the actual hood CFM will never exceed that provided by all the sources of MUA CFM available at the kitchen. If the differential pressure is zero, then one has perfect MUA (pressure balance) and the hood will only be "gagged" by its own baffles, transitions, and ducting. The achieved indoor-outdoor differential pressure won't generally be zero, but it can be kept modest relative to changes on the fan curve. Aim for 90 hood CFM per square foot of hood intake aperture. This should provide complete containment for most cooking for captured plumes using residential hoods with baffles. (Plumes are initially captured if the hood aperture overlaps them.) So, for a desired/required 800 CFM, say, one finds 800 on the abscissa and goes up to a differential temperature curve representative of an outdoor and indoor temperature difference, and thence left to the ordinate where the BTU/hr needed is listed, based on the specific heat of air and the mass of air being moved at that CFM. BTU/hr has a counterpart watts value for electric heating, and also a tons of air conditioning value if one intends to cool. Conversion factors may be found by use of an Internet search engine.

@nvestysly - there is some inadequate advice here (edited to note that some earlier posts here have been deleted). First, regarding hood exhaust noise, you will need the correctly-sized duct that goes from the hood to the outside. Good hoods will require either an 8" or 10" diameter duct. You could have the quietest hood made in the universe, but if the duct is too small, the hood will be noisy due to the amount of cfms being pushed through too small of an aperture. Another factor in hood noise is the number of bends the duct has before it reaches the outside - each bend adds to hood noise. Second, a few people on this forum regularly knee-jerk recommend the Vent-A-Hood. I doubt they have owned one. While the Vent-A-Hood brand hoods work well at exhausting effluent, their squirrel cage design makes them significantly more difficult to clean than a baffle-filter hood. You will have to remove and clean individually the Vent-A-Hood blower shield, then the blower housing which is as wide as some sinks and has very sharp edges, and then the blower wheel which requires a special hex wrench to remove. After cleaning these items, you will have to put them back on. Third, as you already know from your mention in your OP, a hood is going to be noisy because it is a motor mounted at head height. Think of bathroom exhaust fans, which are typically 85-100 cfms, and how noisy they are--meanwhile a kitchen exhaust fan is several times that amount of cfms. What you are looking for is either (1) an "external blower" or (2) a "remote inline blower". An external blower in some ways is the quietest - it is mounted on the roof of your home. However, the noise is simply moved to outside, and your next-door neighbors or perhaps your own family sitting on your patio, will hear that noise. They're also pretty ugly sitting on your roof depending on where on the roof it would be located. Alternatively an inline blower is mounted in the duct. Noise is reduced by distance from the kitchen, and can be further reduced by adding a "duct silencer" to the inline blower. If you decide the above choices are too difficult or expensive, I recommend you look for a hood that has baffle filters (not mesh), and ensure the duct diameter is correct with as few bends as possible. Brands to look at would be Wolf and Best/Broan, or go way up in price to the Modernaire brand. Look, a hood without external or inline blower is going to be noisy, shrug, so is your oven fan and your disposal. I would be more concerned whether the hood works well to exhaust effluent. You must make sure your hood has proper capture area - it needs to be 6" wider than the cooktop, it should be 24" front-to-back, and be canopy-shaped. This post hasn't even touched on make-up air ("MUA"), which you should read up on.

Unfortunately, @jlarsen321 did not return with a description of the system selected, or its observed performance in the context of the cooking to be performed. If one imagines near-perfect capture and containment from a commercial system, and then attempts to squish this mechanical system into the space available in most residential kitchens, including duct placement limitations, MUA system limitations, etc., one eventually finds that the path of commercial system approximation leads to one of two endings. In the first one spends a lot of funds on the higher air flow hi-end residential system that is almost as good as the commercial system, but it fits and is more aesthetic. In the second one spends lesser funds on a system that may be good enough for one's cooking style, or at least better than no system. A story from the past: Once upon a time (1984) a good friend of mine, a coworker and part-time professor, brought his Chinese student to our house to cook Chinese food on our then coil electric cooktop. This cooktop was part of a cooking center with low ventilation flow rate, but perhaps a tad better than the standard ventilation put into kitchens of the time. When it was all over, we were full of great food and the kitchen surfaces were full of oil, requiring a major cleaning job the next day. That began my quest for better ventilation, initially limited to boosting the flow rate in the duct path. Actual competent ventilation was not achieved until the end of my kitchen renovation starting in 2008. So it is not trading off performance against cost that is bad, it is not knowing what the result will be versus one's goals that is bad. My hope is that review of the many kitchen ventilation threads here will lead the wannabe renovator to a considered solution, if not an out-of-reach ultimate solution.