3 Rules for Kitchen Make Up Air Systems: HVAC Training for Home Ventilation that Performs 

In the restaurants where I've worked the make up air distribution comes in the space around the outside of the ventilation hood so that the make-up air comes down the outside of the hood then is drawn back out through the exhaust. This is obv. ideal and maybe not practical for a retrofit in a home kitchen but is doable in new builds or major remodel projects.

Couple of key points. 1. Broan vent hoods can be tuned down to be under 300 CFM., pay attention to the model and look for adjustable controls. 2. The RenewAire and CERV2 can be configured to balance against vent hoods, you need to order the components up front and order the correct sensors and controls; 3. Holistic design should be applied to ventilation: balanced air flow; dehumidification; humidification; dew point control; and cooling. Hint: dew point control is very comfortable. 4. In zones 6 and higher, heating is best done with hydronics, you can’t argue with the physics.

Ever since I had a mold war in my house this is my favorite channel. Thank you sir…. CHEERS

It's nice to see the finished range hood. I'd watched your earlier videos when planning my own vented hood to go over an induction range but ended up going with a regular exhaust with built in fan rather than a liner since I wasn't renovating or building new, just adding ducting and placing a new under cabinet hood where there had been a recirculating one before in a 1980s house. Some day if I ever need to replace the current system I may consider the fantech again with a MUAS, or a relatively quiet Broan if they make it sync up with the Overture system.

Great video. I've designed a split kickboard for the full length with the top 50mm in front of the bottom so the air is diffused. For the fan, I have two (intake/exhaust) operated by one controller. I have a long run so the noise is not telephoned along the duct. Will let you know how it goes when it is up and running.

I subscribed due to your content and being realistic.

I love your content! And thanks for this video!

Love the work you did on this system. Looks like you dumped the quarter end panels that briefly appeared in your previous video. Presume they were in the way and/or unnecessary in the end. I'd try use a deeper hood to recirculate effluent via coanda effect, improving the capture efficiency.

I put our makeup air inlet about 10’ away from the range hood on the kitchen ceiling. Couldn’t get any closer due to a giant 4 ply 16” lvl. Put a normal supply register on it so it looks normal. It pulls air from the ceiling of our screened porch. Our ERV also pulls air from the screened porch ceiling too. Got some custom grills online that match our TG cypress ceiling on the porch.

Corbett, Thanks for an outstanding discussion. You've given me an idea for our retirement home design. A kind of variation on our last home. On my last home, we lowered the kitchen ceiling to ~9' but also had a fun feature where we created a further-dropped arch "box" from one side of the kitchen to the othe as a visual transition. It created, in the rather open floor plan, an arched partition where we had a Sonos speaker shelf. SO I'm thinking that my Makeup-Air could also come in via 4-6 of your pretty plastic grills up there??? 😊 IF air speed is low enough, it might not even create a draft. We're not fancy cooks, so a modest 400-600 cfm hood would do fine? Adjacent to the kitchen would also be the laundry room that would possibly need makeup air. Cheers, Eric

So I just need several dehumidifiers in a row. Thank you for another easy, cheap, and elegant solution! 11:00

So much good content here, and in all your videos, such an excellent service! Wish I could have been FULLY educated in 2019 (pre-renovation)! This video, once again, shows me another reason in hindsight that so many of these fundamental issues to house performance and comfort are swept aside by so many builders. I got a manual-J, and I insisted on ducting calc/manual-D and factoring ACH levels, ERV planning, etc., but I still was given all bath exhaust fans. Now - we are working on the dehumidifier retro and make-up air (shocked by the price for heated make-up air, BTW) All in all, a video jam-packed with great content. Thank you so much for what you do! In the spirit of constructive criticism, I did want to mention context regarding your "offhand" about gas cook comment. For someone whose value comes from digging past the surface beliefs in HVAC, and I do realize it was just a fun throwaway comment but; just like you are schooling a lot of builders and renovators on the essentials of HVAC performance, be careful about rudimentary analysis of other fields. A few things: Yes: *properly-high-powered* quality induction compensates for most all of the gas benefits over traditional resistance coil electric (where the gas > electric adage comes from), principally in responsiveness and heat control, BUT there are a few things that gas excel at, especially in *charring and flambé* , agreed this is a minimal percent of cooks (or commenters on gas vs electric) but also in the broader need of proper *saucier and wok* use where the *non-contact pan sides* are critical to the process, these things are essentially impossible to fully emulate (in one pan) for induction. etc. Induction product lines are still working out some kinks, and I do believe it is absolutely the future, but there are many underpowered, unreliable induction models. I too long for the day when any induction will defeat 90% of even the cheap gas ranges. Let me stress again this is a great video, and aside from the throwaway joke, your video is a goldmine of valuable information. It is clear you are straightforward, honest, and absolutely well-meaning. Keep up the great content, and as a homeowner, I look forward to the day when you've schooled me into total comfort and performance to rival those shown on your channel!

what if you have bathroom exhaust and a stove hood? I see where this will kick on with the hood, but is there a way to have the makeup air turn on with these, or should we look at an erv for bathroom exhaust?

That helped alot mate. Very interesting

I like the floor solution. Another would be to space out the upper cabinets and blow them down the backside or even from above.

I think this is the first time I have seen the completed exhaust hood in your kitchen. Looks great! And OMG why didn't any of my engineers or HVAC people think of that. A return exhaust in the ceiling or on the hood towards the ceiling would have made things so much easier. We ran a vent in the back of the wall through the floor. It was a pain.

Hello, Thank you for the very useful info. Do you mind share where can I find custom hood cover for fantech HL36 hood.

After hearing the pros and cons of make up air variables, I would revert back to cracking your window to help remove odors and leave it at that.

I have my make up air aluminum duct work touching (right beside) furnace and boiler exhaust pipes, which are hot, preheating the air before it hit the main duct work, just before the filter so its properly filter.

Great video as usual Corbett. Long time viewer, first comment but I believe it may be useful. The problem with the condensation underneath the cabinets is that even the best CFD simulations can not predict how the micro-organisms that may have been present in the moist air will move regardless of what happens to the condensation itself or how fast the air is moving. There is (IMHO) enough reason to be wary of such a phenomenon since humidity allows some micro-organisms that would have normally followed what I believe you guys describe as brownian motion to move with the air like much larger particles would. The problem here is if the air is moving at those high velocities and is drying as fast as you say, that may be all that is needed for those organisms to essentially be left behind in that inaccessible and seldom sanitized space. Combine that with the proximity to the floor and the turbulence that may cause, and the persumable absence of light and you may just have a recipe for unwanted dwellers. Then on the next humid day when that exhaust is turned on you may find yourself aerosalizing some things you really don't want. This is pure conjecture of course and is based on observations from hospital environments which are home to an abundance of pathogens unlike the source of your make up air. However I personally would just run a clean mop that is soaked in chlorhexadine (or any chlorine based cleaner if its easier) at least once to ensure that there are no existing pathogens on any of those surfaces and minimize the chances of survival for any future pathogen. It really is beyond belt and suspenders but the staleness and moisture and darkness of that space is so troubling that an hour of your time once is a worthy investment (IMHO). Quick background info, Physician here, 7 years in psychiatry and addiction treatment, since covid moved to public health, infection control department, about to start research for a doctorate (PhD) investigating the effects of different ventilation and filtration strategies on k12 student absence patterns (to track how different respiratory infections' spread may be affected by those strategies). My research proposal was actually very much inspired by your videos that I started watching alongside Matt Risinger's while building my home. Just thought i'd express my appreciation and if you ever happen to be in the UK would love to meet for a chat and show you what we are doing at the University of Manchester.

Just curious on an unrelated subject. I have been unable to find a source I feel comfortable in dealing with well water evaluation. Any suggestions?

For me the best solution will be cracking a window while cooking or drying, where I live the outdoor air quality is good and Its hard to justify spending 10k+ to automate that with mua.

Would your above the fan input air idea be feasible with an 8'-6" ceiling?

Thanks for the video, Corbett. The need for make up air is the limiting factor on how tight a home ought to be, right? What does an affordable MUA setup look like and cost?

So you’re saying you could put a couple of MUAS registers in the ceiling above a standard placed island for example, and that would suffice. Ceiling height would be 10’ so it wouldn’t be blowing on people but would allow the MUA to pull stove contaminants up into the vent like a sort of convection. This setup would seem optimal to me, your thoughts?

I was just about to buy a 900 CFM range hood which will be ducted to the outside via opening in the roof with no make up air. What are the implication? I live in central FL

What about bathroom heat-vent-lights, and vent fans? Do they need make up air? Can bath vents and hood vents be on same make up air?

Thank you so much for making a video that answered all of my questions about make-up air. I'm curious as to your comment about condensation building up on the underside of the base cabinets. Aren't you using sealed metal air supply ducts running from the exterior wall vent right to the supply grills located in the base cabinet toe-kicks? If you are, there shouldn't be any issue with condensation under the cabinets.

probably not code but I sized my makeup air to be larger than the 6" range hood exhaust and omitted the make up air fan allowing the air to be drawn in as opposed to blown in. it may not be fully replacing the exhausted air on high setting but it's better than not having makeup air at all when others in the house forget to open the kitchen window when cooking. I would like to have a system that was fully automatic which would not only open a vane when the hood fan turns on but also turned the range hood on when a burner is activated so my kids wouldn't have to remember to turn on the range hood when cooking

Some manufacturers suggest MUA under the stove if possible. Sounds like a recipe for rusty stove. In existing homes, that's nearly impossible and not practical for air intake source. Some Laundry room or any room next to kitchen can be a better option for MUA entry. I have wood burning fireplace that I uses all winter long and imagine the difficulty of fresh air intake location... ;)

8` ceiling, how about the return air in a kitchen skylight well?

Thought provoking...

We are in the middle of a new build. Will an ERV dumping into our main duct work provide enough air a range hood?

Awesome content as always, Corbett! We’re currently designing our forever home and I’m dismayed that I can’t find any wall/built-in ovens that are designed to be direct vented. When I cook bacon, or other fatty meats in the oven, I’d really like to vent those fumes. Have you found any ovens with direct vents, any good work-arounds or is this just a ridiculous idea!? Im considering intercepting the vent on the bottom of the oven and connecting it to a duct with an exhaust fan that will be used for both my range hood and the oven. It would be controlled with a damper and a multi speed fan. I tried writing this comment the other day but I don’t think it worked because I can’t see it anywhere. so I apologize If this is a repeat. TIA!

Are make up air systems required for homes without any gas lines even coming to the house? Our electric stove hood vent is over 400 CFM and the inspector won't pass our kitchen remodel. I'm not sure he knows that there aren't any gas lines coming into our house or even neighborhood for that matter. We live in Fairfax county Virginia.

Could you use a heat exchanger linked with the rangehood? With a bypass option depending on outdoor air? Just wondering about ways that arent a heater to preheat

Is that a 24” wide oven?

Is fan driven makeup air necessary? I was thinking that a backwall passive (with filter and powered damper at entry point) would be the way to go. What is causing the velocity out of the makeup air register to be more than the hood's own draw? I would thing the makeup air would be following simple path of least resistance relatively straight into the hood. No?

Take care with that cosori air frier model. There was a recall recently. I’m pretty sure that model will qualify….it could set on fire when plugged in

I hear you on comfort in the bedroom with a higher temp and lower humidity but I will indeed challenge you on the best temp to hack your sleep. 65 degrees is the temp most functional doctors and bio hackers recommend for the best/most restful sleep. Just giving you some crumbs to get your gears turning for when you consult on my home build 😊 Nilima and I promise to make this engagement fun and challenging!

For minimalists checkout: Messana ATU; Building Equinox CERV2; RenewAire ERV. You can program your ERV to be a makeup air unit. But you need to add sensors and additional controls to the system. This may be above the capability of your local HVAC company, but it can be done, if you are willing to put in the time and efforts. Programming skills are required….but you can avoid the cost of additional equipment.

14:20 Introducing make up air from above. What prevents a short circuit where the make up air is pulled in at the bottom of the hood, "ignoring" the cooktop or range below?

Can I just open my sliding door when using my hood at high CFM settings? It's about 20ft from the exhaust.

I'm curious to know if anyone though of doing a linear diffuser style around the cook top, flush to the counter, for the make-up air? That way the air coming in to the house would technically be jetting upwards toward the range hood anyway, aiding further by essentially creating a curtain air stream around the cook top which would contain the cooking vapors. Thoughts?

Why not bring the make-up air around the cooktop surface? Just a few inch perimeter at the same level (height) as the cooktop. This is what I have done with mine I have brought in an 8 inch round duct into the cabinet underneath the cooktop which is acting as a plenum of sorts and then have a vent grill around the cooktop about the same size as the "overhang" that is recommended for the vent hood. So my vent hood is roughly 20% (which equates to 10cm) larger than my cooktop so I surrounded my cooktop with a 10cm grill for makeup air. The thinking was that since this air is unconditioned anyway, I do not want it mixing with my kitchen air, and I also dont want it blowing on me as you recommend, so I ditched the filtration as well and wanted to keep it as close as possible to the source of the pollution. One last consideration was that the air velocity was the highest in the center of the hood so I wanted air to come in from all around the cooktop (pollutant), and be pulled upwards and inwards towards the exhaust hood. It also helps that this was done in the hottest country in the world (Kuwait) which is my home country. Im hoping that the heat of the makeup air would furhter help in moving upwards towards the exhaust hood. I havent had much chance to test it since I moved to the UK but would love your thoughts on that method.

So, if I understood this correctly, the make up air needs to be blown in with an equal cfm? It can't be passive?

In the long run i would be very nervous about having the make up air in contact of plywood or any other cabinet surface.....i would prefer to have the make up air at the hood itself...

Kitchen exhaust / makeup air is difficult, yet builders have been blistfully ignoring it for years. Is there a compromise solution?

This is how the 2020 Florida Mechanical Code reads -- look at the exceptions: *_505.2 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._ _Exception: In a single-family dwelling, makeup air is not required for range hood exhaust systems capable of exhausting:_ _(a)Four hundred cubic feet per minute or less; or_ *_(b)More than 400 cubic feet per minute but no more than 800 cubic feet per minute if there are no gravity vent appliances within the conditioned living space of the structure._*

There are a few good videos out there showing makeup air built into the hood cabinetry. They use smoke to show The flow of air and it looks to be the best option out there. Passive makeup air. Actual observations be your silly theory

We need some better microwave hood exhaust fans and ways to retrofit makeup air into existing homes.

now that i think about it a little more , my first question is worded poorly. A better question would have been - have you ever seen anyone use a light commercial ERV 250-540 cfm as a range hood exhaust fan system, my thinking is , since erv's are already made to be balanced , recoup heat / cooling and to help dehumidify the air it could be an all in one solution, a guy would just have to fabricate a range hood, filter the grease in the air and have a control point. - thoughts?

why don't you bring the make up air in through an erv that is solely used for make up air? is there any cons / pros to this concept? is it a dumb idea? wouldn't it be prudent to try to recoup the heat/cooling from the exhaust air also if i recall correctly erv's also help with humidity.

I prefer about 64ºF indoors. Sleeping I like it 60ºF or cooler. I find anything over 70ºF uncomfortably warm indoors, whether 5% or 50% relative humidity.

Critical Point ☠️: Inasmuch as I don’t want air blowing on me, I certainly don’t want to die from Carbon Monoxide poisoning. This is the most important factor when looking at make up air in an air tight home. Let me explain why: you’ve built an airtight home and you energy rater is giving you gold stars , and your home chef of a partner can’t wait to get into that kitchen and celebrate. The exhaust may actually not be capable of pushing the odorless and deadly gas/fumes out of the room - it can’t fight the air tightness. In old homes this was not as much of an issue for this specific reason due to make up easily air finding its way through drafty windows , doors, attic hatches etc. - just like you wouldn’t want to sit in your garage with a running car. Ideally Energy Raters will have to do field verification of this , as it will save lives.

It would be great for you to be more thorough in explaining how to go about the makeup air in hot and humid climates. Are you just ignoring the fact that the incoming outdoor air is humid during summer? I wonder if the makeup air can somehow be tapped into the existing ERV+dehumidifier setup

Don’t you already have a dehumidifier built into your hvac system?

Why wouldn't your make up air be tempered and mixed on your supply side? 2 simutaniouse dampers one that let's the fresh air in and one that opens and increases that rooms cfm.

I believe you've said in the past that "Comfort' is subjective (if not, I've heard it quite a few times in regards to HVAC) That being the case, your 75 degree 50% humidity works for you where others may vary a little in both temperature & humidity. I keep my home in Minnesota @ 67 and shoot for humidity around 40%+ (But I've got a 70's 2 story W/basement so It's an ongoing situation)

So Corbett, next time you won’t locate make up air duct thru the kick board?

yeah its gonna be a toe kick full of mold. Pretty sure. Look at a bathroom exhaust vent. In time they all get mildew covered or mold covered.

When I need make up air, I just open a window. Why put in windows with screens that vent air if you're not going to use them.

I think the cat would add "Don't dump air on cats!"

@Home Performance I feel a bit called out about the 68 degree thing. I think we are going to have to agree to disagree. I personally can't live above 68. Even in the middle of winter, I don't keep the heat above 65, and that's with a reasonable humidity level in the 40% range.

we have made these houses so tight that now we have to spend several thousand dollars to do something that the house used to do on it's own... for free... we are requiring these houses to be treated like a yeti cooler.... but I've never seen a yeti made out of wood... JMO

A 10 kw heater would be to much for a 600 CFM…

Lots of ❤❤❤ "stupid" ❤❤❤ in current codes.

Pretty sure if a person’s feet are 75 degrees it’s because they are not alive.

The more I hear about these hyper-sealed housing it seems to be using $ 1000 to chase $10 plus’s a lot of additional maintenance to balance ventilation and makeup air while controlling enthalpy. One thing your bio hacks don’t seem to take into account is age 68 deg can be deadly to older folks .

Or you could ignor the make up air, and just open a window when you are cooking.😅