Edit: Thanks all! I confirmed with the contractor that the "dump in mechanical room" was actually dump into the return air plenum, just extremely poorly worded. This seems like both the cheapest AND best option, so we're definitely going that route!

Hey folks,

I've got a new construction, large kitchen reasonably open. I'm installing a 48" 1200 CFM hood - I've got a 30 inch induction range and a 15 inch 22k BTU gas module that we will mainly use for wok cooking. This requires makeup air due to code. An important note is that I'm in Michigan, where it certainly gets quite cold in the dead of winter.

I was presented with a few options by my HVAC contractor for how to set this up (all with automatic dampers):

1. Air comes into basement mechanical room and is just dumped there
2. Air comes into basement mechanical room and is ducted into the kitchen
3. Either of the above but also heating the air as it comes in

My questions are twofold:

1. Is it OK to dump it into the mechanical room? I would presume we end up with an updraft from that room through the hood, but I'd like a better understanding of whether this will successfully prevent depressurization. I've got a gas-heated tankless water heater and two gas fireplaces, but no furnaces (using Heat Pumps).
2. In either case, how big of a deal is the air heating? It doesn't really matter to me if the mechanical room is colder, however it will obviously leak to the adjacent locations. If we duct to the kitchen, it will naturally pick up some heat while going through the ducting, but unclear how much.

Thanks!

PS I did some searching but couldn't find a discussion of this topic - though it's definitely possible I just missed it.

PPS I'm not currently looking specifically to relitigate the "how many CFM is the right CFM" conversation, but happy to get more advice