You can put an electric heater in the MUA. Turn it on when it's cold.

Thanks for the suggestion. I've read they use a ton of power, and that doesn't solve the problem when it's hot out. Unfortunately in Michigan, annual temperatures swing both ways. It seems like having a dedicated duct for the air make up localized the temperature difference to the kitchen, where the thermostat isn't located. Connecting it to the return plenum will at least distribute the unconditioned air, past the filters, and into the rest of the house where the swing won't be as great and the thermostat could pick up the difference. I was wondering if that's still allowed. My HVAC installer says that it isn't. Seems odd.

I just spoke with my builder again and he said there's no getting around a dedicated MUA line for the kitchen exhaust. The newer code states the HVAC system has to be balanced so we can't add the MUA to the return plenum because it would imbalance the system. Filter and conditioning the MUA air isn't required so I guess we'll just need to learn to deal with it.

1100 cfm sound's like something more suitable for a small commercial kitchen than residential. I don't think you realize how much and how quick 1100 cfm will purge air from your house if connected to ac return. I don't understand your reason for making the whole house uncomfortable instead of only the kitchen. I also believe you don't realize how easy it is for the dampers and sensors to fail in a system like you want. When it screw's up in a few years hvac people that don't know about it or not understand it will chase their tails for goodness knows how long and at what expense to you trying to figure out why your hvac isn't working well. Let pros do it the tried and proven way,be happy and concentrate on other things you better understand.

Thanks for the input. If I'm correct, for our 5000 square foot house with 9 foot ceilings, I calculated it would clear the house in 40 minutes, which I admit might be overkill. We chose the hood with a proper air capture aperture and the range top we're using has a charbroiler and griddle, in addition to four burners, so I wanted more overkill versus smoking up the house when I want to grill something. I've seen some examples online of MUA's piped into the return air plenum which makes sense to me since the air will be filtered and evenly distributed to multiple rooms. The distributed drop in temperature across (more or less) all rooms would see a lower temp delta vs all the temp delta in one room, namely the kitchen. Also, with the variable speed blower in our geothermal system, our HVAC installer says it almost runs continuously so the potential MUA would be immediately conditioned before hitting the house. I'm not questioning our installers expertise. Just trying to understand why the code would call for an unconditioned and unfiltered air source drawn directly into the house when other codes seem to be aimed towards tightening up the house and increasing efficiency.

I would keep the MUA in kitchen only. A colder kitchen is more acceptable than lowering temp across the whole house. With the kind of output you stated from your range, I dont think anyone will feel the cold standing in your kitchen area.

"Filter and conditioning the MUA air isn't required so I guess we'll just need to learn to deal with it."

It may not be required but it is desired. The HVAC guys should be able to determine the size of a suitable filter (so as to not have a large pressure drop across the filter) and create a box for it. There should also be a screen of some sort on the outside entrance to keep out undesirables (insects and such). Heating can be done with an inline thermostatically controlled heater(s) that should be able to raise the temperature during winter, but not purposed to heat the whole house.

Thanks for the info. I'll talk to the HVAC installers about sizing a filter and box for the MUA duct. Too bad someone doesn't make a kitchen hood ERV. I guess all the potential grease would gum up the outgoing exchange radiator not to mention the air restrictions it would create.

Not to rain on your parade, but I'm pretty sure you dont need a 1100 CFM range hood... Unless of course you are running a japanese steakhouse in your house. You know the ones where they perform for you.

Also, do you know how loud that will be? I prefer something 300 or less due to noise. I have tried higher CFM hoods and promptly returned them, they are inherently noisier. Cannot even talk to someone due to the noise. It is possible to reduce the noise a bit if you increase the duct size. Do you have an idea what the duct size is for that range hood?

And, super inefficient in a cold region like Michigan, pump all your conditioned air out and suck in cold air that needs to be conditioned again. CFM should be just enough to get smoke, steam, and smells out and that's it.

Thanks for the comment. It's a 10" duct and the blower is inline remote with a muffler. It's all on the exterior of the house past 10" thick ICF walls. The blower itself will be suspended by porch rafters to reduce vibration transmission and the porch rafters are tied to the house with a ledger board on the exterior of the ICF so there's little to no vibration transmission into the house. The inspector is requiring a 10" MUA duct.

I know that at full blast, it's not going to be whisper quiet, and I'm only expecting to use it full blast in rare occasions, but we do want the option for that many CFMs. As I mentioned above, the range top is 48" with four burners, a char-broiler, and a griddle for a total output of 111000 btu. I doubt we'll ever use everything full blast at one time but my biggest concern is smoke from the char-broiler and grease/oils from the Chinese cooking I frequently do. The MUA will come through the toe kick of the range top base cabinet so it helps create an air curtain to pull out smoke/grease/oil. Believe me, I have the same concerns about cold/hot air in the MUA, but to achieve the worst case scenario for cooking containment, we need to look at corresponding CFMs.

I'll have to see how the controls open the MUA damper. I wonder if it's the case where the damper only opens over 500 CFMs, but I would imagine that with our tight house construction, we might not want that.

There are two ways to control the damper. One is electrical, and it is controlled from the fan switch (via relay usually) when the fan is above 400cfm or so (or all the time, whichever you prefer). The other is barometric, where the damper opens when the pressure difference inside the house falls below a certain level.

Dazureus,

In my research for makeup air units, there are two choices for heated make up air:

• Fantech
• Electro Industries

Take a look at them. Each manufacturer has a couple of install options and they both heat the incoming air. There is also a lot of information on the Appliances Forum about makeup air.

Best of luck!