The 2009 code in many cold weather states require MUA systems for over 400 CFM M1503.4: "Exhaust hood systems capable of exhausting in excess of 400 cfm shall be provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system." "Makeup air required: Exhaust hood systems capable of exhausting in excess of 400 cfm (0.19 m3/s) shall be provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system." A2 is strictly enforcing this. I decided to go induction and stay under the 400 CFM. I was leaning toward induction and this just tipped the scale. I am probably going with a Broan evolution hood @ 350 CFM and 4 halogen bulbs using theater lighting. The zephyr genova is very discreet, but concerned that the single fan on the left might not do the trick (only 250 cfm). The ventahoods have a true HEPA filters. I figure A2 is pushing me into the future. If you go too high on CFM, there are dangers, so I plan to avoid the problems! Good luck!! PS - I plucked the Wolf induction on sale. Love the appearance of the surface and had no trouble with the controls - I used my knuckle to tap the power up and down when my fingers were slimed! I liked the large burner and the set up of the burners and only one cook as my husband only knows how to order pizza and not cook. I only tested it at the appliance dealer, so can't wait to the kitchen is done and I actually can really test it.

@astase sorry to hear about your experience. It's extremely unfortunate you had an inexperienced Installer to execute professionally. I can assure you a talented & most qualified outfit. To generalize an open statement to the masses is unfair to those who can execute successfully. If you'd like, I can help direct you to the most qualified installers. We can help you link up with with manufacturer

"I read somewhere that to heat MUA unit that is balancing a 650 CFM hood you nneed a furnace big enough to cover a Bill Gates-type house." No idea where that came from but it's quite erroneous Hi opaone, yes I made a typo: it should have been 900 CFM not 600 CFM. I was just trying to make the point that it had been noted we need to have a lot of heat to warm the make up air, and I don't know how to get this done without having some massive framing work and pllumbing and electrical too. I believe I got that from a post up thread from kaseki about four years ago. He wrote: "For example, 900 CFM is 54,000 CF/hr being raised as much as 50 degrees (more in N. Minnesota). This would be equivalent to a house volume (assuming no leakage) of 270k cu. ft. being heated 10 degrees per hour. A 27,000 square foot house with 10 ft ceilings would be of this volume. Lacking a Bill Gates' house sized furnace, you may need supplemental heating." Now, your link to Electro's electric MUA heater is really interesting. I had seen Fantech not this. Both big and costly! The daily use cost is what I wonder about, and I don't see any reviews (at least not at supplyhouse.com). Of course, operating these varies based on one's power needs/costs, and where I live electricty it not cheap. I am incapable of calculating what my daily use cost might be, using the Electro model MD-10 as an example (designed for 600 CFM fans), the specs are beyond my skill level to assess a cost to run the thing. I do see that unit has a 10" duct, and puts out around 34K BTUs of heat, which is about what I was planning to use to heat the additon in its entirety. Heating a house in my area, using electricity, is not considered the best option as I looked at an electric combi boiler and was reading comments and this was pooh poohed.... You did a good job of explaining the best- to worst-case examples of brining in the MUA, and of course like an idiot I cut a nice big fat 6" hole in my rim joist so I could bring the air into the middle of the LR/kitchen via the ceiling, which was the worst option you very intelligently noted. I learned a little about air flow reading a paper from the dept of energy website where they talked about throw and how the air hugs the walls, etc. Balanced vs supply vs exhaust vs ERV/HRV and how all of that relates to this thread makes the whole topic in general complex for the layperson, and as mentioned previously: good affordable help these days is... hard to find. These types of threads and forums are all most of us have! Thank you for your valuable contribtions.

@myira - There is excellent advice above. I wanted to share two stories about my last house. We were moving from out of state with an infant and depended on our realtor and home inspector for a lot of things. Unfortunately the house we purchased was owned by a cheapskate DIYer sort and we spent lots of money fixing plumbing and electrical hazards that should have been caught on the home inspection. We were BFFs with the plumbing and electric companies. Both commented that they perform home inspections and that for a service charge will home out and look over a house someone is considering purchasing. I wished we had hired them to do a walkthrough in addition to the home inspector. It would have alerted us to a lot of problems for just a couple hundred dollars. Eventually we wanted to add on to the house but decided to move to a different place nearby to accommodate our growing family. We sold the house as is to a realtor who was also a house flipper. He made lots of cosmetic changes and we were very up front about issues we were planning to correct prior to moving such as new roof, rotting window, HVAC needing updated to properly service the bedroom wing, etc. None of those important things were improved or fixed when he put the house back on the market a few months later. I’m unsure of what he actually disclosed to the buyer. This is what concerns me about your situation so I’m glad you are seeking opinions and proceeding carefully.