Now reviewing the appliance order, and the supplier wondered if we should have the 600 cubic feet per minute (cfm) model instead of the 300 cfm model.
How much suck do we need?
We are getting our hood from Vent-A-Hood (not to be confused with Robin Hood...):
Beautifully minimal and the proper length for our goofy linear cooktop. But which size?
The well-aired folks at Vent-A-Hood suggest a 600 cfm capacity (which is really 900 cfm according to their chart) for a run-of-the-mill (that is, non professional) gas cooktop (apparently gas cooktops require more suck [about twice as much according to these guys] than electric cooktops). Sucking 900 cfm is a whole lot of suck. Of course, a larger unit costs more (and results in more profit), so I'm not sure I trust these guys...
eHow suggests a calculation that includes the volume of your kitchen plus the BTUs of your range. Our kitchen is 13 feet long by 12 feet wide by 9 feet tall, which equals about 1,400 cubic feet. eHow says that the Home Ventilating Institute (now THAT would be a fun place to work!) suggests the fan be sized to change the air in the kitchen 15 times. So 1,400 times 15 equals 21,000. Dividing by 60 gives 350 cfm. eHow goes on to say that you also need to add 100 cfm per 10,000 BTUs of your cooktop onto that number. Our range puts out 7,000 watts, which converts to about 24,000 BTUs, so we need an additional 240 cfm bringing the total to 590. So this suggests we need a 600 cfm unit.
Since eHow could very well be written by eDiots, I decided to verify what the fun folks at the Home Ventilation Institute actually say, and they say something different:
So according to these guys, our 48-inch hood requires a minimum of 160 cfm with a recommended suck of 400 cfm. The 300 cfm unit by Vent-A-Hood, which is really 450 cfm (according to them), should be plenty sufficient.
KitchenSource recommends 150 to 300 cfm for an electric cooktop and 100 cfm per 10,000 BTUs for a regular (non-professional) cooktop (that's 240 cfm for us).
300 cfm is enough suck.