Modernaire and C C B Innovations have some videos that I found really helpful.

Although, your HVAC guy may be correct. Where I live MUP is only required for extraction fans over 900CFM's and in newer homes which are more air tight. I'd check with your local inspectors office first.

This post was edited by Cori4137 on Wed, Jan 14, 15 at 8:12

There is a lot of conflicting advise about MUA out there and even on this forum. I posted a link to GBA, and they discuss it a lot. If your HVAC guy says you dont need one you may not if you live in an old house with lots of cracks.

The problem is if you do not get one and actually need one the range hood could create a backdraft off of your other appliances.

Martin Holliday does a good summary toward the bottom in his "Avoiding Problems" section.

Ive never had an actual range hood so cant offer any first hand advise. I live in a 170 year old farmhouse so you can imagine the leaks. I made smashburgers last night and my little recirculating hood didnt even get clise to keeping up even though I turned it on before I started. My next house though is going to be super tight so I have tried to read about MUA.

Here is a link that might be useful: Green Building Advisor MUA

I've got my make up air coming in through the floor under my range (I didn't want to see the vent on my wall). The air comes in from the outside (under my deck) through its own duct. Whether or not you need it is usually determined by town code. In my town, anything over 600cfm requires MUA. Hope that helps!

In my jurisdiction, anything over 450 cfm requires MUA. Check your local code to see what is required. If not required by code, I honestly wouldn't bother. You could crack a window whenever you are planning on running your vent on full blast. The equipment and installation of a makeup air system with damper will likely run you close to $1,000. Cracking a window is much more cost-effective!

Thanks for the feedback and tips. I have been blindsided by this issue so I have been trying to learn. What did we do before the internet and Garden Web?

IowaCommute, that Martin Holliday link and its associated links are very helpful and I learned lots from them.

Julie1973, does your MUA just come straight into the house unfiltered or does it get attached to your home HVAC system? The instructions with mine indicate it should be attached to the return air ductwork which means it will need a filter as well.

http://zephyronline.com/docs/brand_essentials/products/specsheets/mua_spec.pdf

Finding clear information about codes from our city is difficult.

I wish more attention was given to this important venting component!

Our kitchen renovation included a Zephyr exhaust fan/hood, and starting in 2014 local code required MUA if the exhaust went above a certain cfm (I think about 450). However, the fan could be jumpered so that it could not exceed that minimum, so we left it that way for inspection. After the final inspection we went back and jumpered it so that it could go to the max cfm.

As far as I can tell the inspector never even checked for makeup air for our 1940 house (which is not that tight), but at least we were ready for the question.

Bruce

When I mentioned to my GC that I was having trouble finding a hood fan with less than 400cfm, he said what he usually does is installs an air switch in the vent pipe. When air is going through it, it trips a switch in the furnace to turn on that fan. The furnace pulls air in from outside, (heats it if necessary) and then sends it through the vents in the house.

I found a fan that works for me. So we aren't hooking this up. But it sounded a lot cheaper and easier than I originally feared.

Most HVAC systems cannot handle having 600 CFM+ dumped into their returns. Home HVAC systems simply don't handle that amount of volume. That's why a separate heated duct into the home is required in a cold climate. It takes a lot of BTU to overcome a -10 air coming into the home, and the range vent exhausting the whole entire volume of the house within 10 minutes of use! That's why MUA in a cold climate is both complex and expensive. It gets less so in a more temperate climate, but it doesn't change the basic physics of needing to replace the air that you are attempting to exhaust out of the house and the potential for backflow of other home penetrations.

Not sure if loveswindowsanddogs got all the answers needed but here is a short Broan video that may be helpful to those that need some clarification on the basic concept of make up air and why you might want or need it.

It took me awhile to find info that made sense and was separated from the regular HVAC stuff. To make your furnace do the work of balancing your hood fan didn't seem logical to me so I kept looking. There are lower cost alternatives to expensive independent heated make up air systems for those that can't afford them or don't live in an extreme cold location and several locations to put them around your kitchen that seemed to have good results according to different websites/videos. Of course, depending on your size of hood fan and local codes and if you are down to studs or just trying to squeeze something into an existing area will affect what you will be happy with or maybe just what you can live with. Here is another video of one such option given by a guy with solid advice that I have referred to several times over my huge, to the studs remodel project.

This is the system we used and it seems to be functioning fine.