I have always wanted to have a good kitchen hood, jokingly saying things like “powerful enough to suck a small animal out of the kitchen.” We are going with an induction cook top, so really no need to go that crazy with the hood, but we picked a 600 cfm Faber pull-out hood.
At >400 cfm, technically per International Residential Code (IRC) 1503.4 you are required to have a make-up air system that can replace air being sucked out by the hood, and it needs to operate when the hood is operating.
Our HVAC subcontractor’s proposal included a $7580 option for non-tempered kitchen make-up air, using a Fantech inline fan and some other bits and pieces, I think the explanation was that this system would replace exactly what was being sucked out so things would stay in balance. But non-tempered, so cold air coming in during the winter and hot air coming in during the summer. A heater option for another $2310 was also served up.
The other option that was presented was a “ventilation control system” utilizing an Aprilaire 8126, for $1210. My understanding was that this would allow outside air to come in when the kitchen hood was running, not as precisely as the first option, but it would help keep things roughly in balance and comply with code without breaking the bank. So we signed up for this option. Note that we also signed up for a HRV option, a Fantech SHR1504R which is supposed to bring in up to 149 cfm, so we were trying to be thoughtful about fresh air in what should be a pretty tight house.
After the install I noticed an Aprilaire controller on the air handler that the Aprilaire 8126 was hooked up to, which controller allows you to set the damper to open for a certain number of user-selectable minutes per hour, and when the damper is opened a signal is sent to the air handler so its blower runs, pulling fresh air into the house. That didn’t seem like makeup air to me so I started asking questions.
The HVAC sub eventually agreed that the Aprilaire 8126 should operate in concert with the hood. The initial idea was to use a current draw switch on the hood load, and the gentleman I was speaking with mentioned that it would be neat if there were some sort of a pressure switch that could be used. So a little more homework, and Faber actually makes a kit that would have been perfect for our application. I called Faber to see if I could just get the pressure switch, since we already had the damper installed, and they referred me to the manufacturer of the switch, CCB Innovations. I called them and they are supplying a 6″ collar with the switch, which we can then hook up to the Aprilaire 8126 (after running a wire from the hood to the damper, which may require some demolition). The full switch/damper kit is in the neighborhood of $300 from either Faber or CCB Innovations, and the kits purport to satisfy the IRC code for make-up air. It also looks like Broan makes some similar kits, though the switch looks different and does not come mounted to a collar. This is not a commercial kitchen and it is just two of us in a 2500 sqft house with a moderately sized hood, should be fine for our application. Strange that neither of our HVAC sub or general contractor were on top of this.