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Makeup air dilemma - WWYD?

Posted by Mgoblue85 (My Page) on
Tue, Nov 19, 13 at 21:04

I have a question regarding make-up air options. My city in the state of MI enforces the makeup air requirement for any hood above 400 CFMs, which I knew, but I was not quite prepared for the exorbitant price. I was planning for a 1200 CFM internal blower BS hood. My house is a 65 ranch and not air tight by any means, so what would you do???

Switch out the blower - any ideas on a 400 CFM blower for a 42" hood?

Buy a different hood - any ideas on a wall mounted hood with a 400 CFM blower? I won't have wall cabs.

Or is there another option for reasonable makeup air that could possibly work? Appreciate any help!!

Btw - range is a 36" all burner BS. Also x-posted on Kitchens to cover all bases.

Follow-Up Postings:

RE: Makeup air dilemma - WWYD?

If you require heated MUA you need a custom( read expensive) system.

If not Residential Makeup Air System (RMAS) from CCB Innovations might do the trick.

"By creating a makeup air infiltration point localized to your kitchen ventilation system, the air is replenished at a slower and more controlled rate during the operation of the kitchen vent hood. To do this effectively, the operation of the kitchen ventilation system needs to synchronize with the operation of the motorized fresh air damper. The damper needs to open only while air is being exhausted from your kitchen and remained tightly closed when not in use.

Synchronization of the fresh air damper with the kitchen vent hood can be achieved using the Residential Makeup Air System (RMAS) from CCB Innovations (patent pending). This allows the operation of any kitchen exhaust system to connect to a fresh air damper 3-5ft away from the exhaust hood to bring in fresh, clean, healthy air to balance the pressure change in your home.

By maintaining an equivalent air exchange rate, the potential for negative air pressure during operation of your kitchen vent hood is significantly reduced. This will provide a healthier and cleaner air supply inside your home.

Even if not required in your area for residential homes, installing a fresh air intake with a high CFM kitchen ventilation system is always a good idea. And because the Residential Makeup Air System (RMAS) by CCB Innovations is universal to high CFM vent hoods, it can be installed in any new home, or even retro-installed, in an existing home to provide a cleaner and more balanced air supply for you and your family,"

Here is a link that might be useful: LINK

RE: Makeup air dilemma - WWYD?

There are a lot of threads on this forum addressing MUA, and for the most part these are worth skimming. There is also information in references in my My Clippings.

Given your location, at least heating of the air is needed, and unless you are an experimentalist, an engineered design is probably most suitable.

A triggered fresh air intake like that described above can be your starting point, but the easiest heating scheme would be an electric coil element in the airflow that is controlled by the intake air temperature.

The mention of 3 to 5 feet away is not necessary; best is to inject the air into the house or kitchen in a way that it doesn't disrupt the rising effluent from the stove that is to be captured by the hood.

Note that the point of MUA, from the inspector's point of view, is to keep the house pressure from going too negative and thereby backdrafting combustion appliances. If you want to filter the MUA, or have an elaborate setup causing pressure loss along the MUA path, then fan boosted MUA may be needed. If I weren't an experimentalist, I would examine Greenheck products to see if any are suitable for residential use. The overall cost may be commensurate with hiring an experimentalist posing as a HVAC contractor. :)


But wait, there's more

To answer one of the questions, the flow rate at the hood aperture should be in the ballpark of 90 cubic feet per minute per square foot of hood aperture. This is actual flow rate, and what a 1200 cfm fan can actually move will depend on the pressure drops on both sides of the fan. A big one of these pressure drops (usually called pressure loss) is the MUA supply pressure loss (pretty high if only house leakage is considered and one is trying to pull air flow in the 1200 cfm range).

The MUA requirement may be waived in some communities if you have isolated all of the combustion appliances from the kitchen; that is, you have given them their own source of (considerably lower cfm) MUA. In such cases use a window and don't grill inside in the winter.

Otherwise, the information is out there, but the cost is never trivial. Pro cooking on pro-style ranges requires pro-level MUA and scaled restaurant-level MUA cost.


RE: Makeup air dilemma - WWYD?

Thanks Deeageaux and Kas for the info. I've been combing GW and any other site I can find to read all I can on mua and what solutions people have used to accommodate requirements. I will follow up on what you have provided. Thanks for taking the time to respond.

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