Matt, I’m an electrician in Georgia. When I tell mechanical guys and GC’s they need make-up air, they look at me like I’m crazy. Had a customer on a recent job call me and ask why his house smelled so bad when the exhaust fans were on. His house was so tight, and with no make-up air, the exhaust was breaking the seal in a P-trap and you could smell the septic tank. Repeatedly told the contractor we needed make-up air on that one. Now they just crack the windows.

I've seen systems that dump makeup air around the perimeter of the hood so that it doesn't mix much with the already conditioned air. That to me sounds like a much better solution. This one will dump hot, humid air in.

5:38 An eight-inch circle has an area of about 50.3 in². A circle with three times the area (i.e. ~151 in²) would have a diameter of 14 inches, not 16 or 24.

New science for me. Thank you for the class Matt. I’m sure lots of us appreciate you not only as a mentor, but something like a brother.

Good stuff Matt! This is a difficult thing for most homeowners to understand but really is important.

Great video. This answers a question I've had for a long time, and is directly relevant to your video about radon gas. I live in an older house with a non-encapsulated crawl space in a high-radon zone. When I turn on the kitchen vent or even a bathroom fan, I try to simultaneously crack a window, because I know that the negative pressure is going to suck crawl-space radon gas through every gap in the subfloor, un-caulked electrical or plumbing hole, space around HVAC registers, or even improperly sealed ducting in the crawl space.

Great content. I had assumed that a passive make up system using a fan triggered relay would be sufficient. Your video was very enlightening on this subject. Keep up the good work.

Excellent teaching video every customer should watch this In all my decades I have only seen one properly installed fan that was not installed by me. I like to boil for very large pots or frying pans of water on all four corners of the burner simultaneously with the fans off just as a demonstration to show the customer how much bleed of smoke or grease that would be coming into the house. And then I turned their fan on to show them how their improperly installed Fan it’s still rolling over and bleeding around the edges into the house if it was invisible burning cooking oil or other VOCs and particulates. And then show them a before and after I correct the problem or just re-install their fan and ducting correctly if possible. And show them the difference when you open up a kitchen window or adjacent room window. What happens to the airflow.

Great video Matt. The use of the manometer really helped illustrate the concept of pressure differentials and the importance of balancing ventilation.

I used to work as a chimney sweep. We would get calls all the time for smokey fireplaces due to downdrafts. Much of the time the issue was a tight house with a strong kitchen exhaust fan. Half of the rest was no make-up air for the furnace. Then it was stack effect, those big open staircases that are all the rage right now. Finally, in about 1% of the cases, it was some issue with the chimney (usually location of the house) which resulted in outside air pressure creating a downdraft.

Thanks Matt, this video comes at the absolute best time for me! I am getting ready to remodel my kitchen and I've been looking at cooktops/rangetops and corresponding hoods. Thanks for the valuable information!

He gives much great information for a weather tight home. My ranch house built in 1963 has a full below ground basement. Moisture and radon are a concern. In the winter the forced hot air furnace sucks the basement air into the furnace and out the chimney. The air gaps between the foundation and sill , plus the basement windows provide the needed air exchange . This also removes radon in the winter. In the summer I just open the windows. I am not using any extra electricity. Gas stove and exhaust fan . I do use an air filter system in the spring to remove pollen.

Note also: an incorrect draft into the home will reverse the chimney draw and you wake up dead from Co Their phemonom also and sometimes happens in a atmospheric temperature inversion. Warm air get trapped under a pocket of cooler air (in the clouds) setting off everyone's Co detectors. A false/positive.

Similar science, albeit applied differently, to what I deal with at work. Indoor ranges for military training have precisely tuned intake and exhaust in order to flow a specific cfm, but at all levels. Floor, waist, head, and ceiling across an entire room and for the length of the facility. Sometimes as much as 100 meters. All to ensure that the spent gases and lead particles are exhausted and filtered properly, maintaining soldier health. Nice video showing the importance of fresh air, especially in tight homes.

When eight inches isn't enough. The 3:1 passive rule of thumb has served my company well over the years. Fighting with customers over the need has never been fun. I appreciate these videos from Matt. I have customers who will believe the Internet over me. After all, I can't possibly be motivated by anything but greed, right?

I put a large exhaust fan into a new room I built and the entry door which opens away from the space did not want to open with the fan turned on. I was impressed by that. I'm still trying to figure out a fresh air source for that which isn't ugly or drips in the winter, so I was glad to find this video.

Matt, great mention about induction. I was really on the fence about induction for my remodel and your videos about induction really helped change my mind. I love my new induction cooktop. It's faster, more responsive, and I feel is safer than any cooktop I have used.

A whole house ERV or HRV with variable speed blowers controlled by a manometer that constantly monitors pressure balance… would be a nifty way to modulate makeup air to continuously maintain balance regardless of which or how many bathroom and kitchen exhaust fans in the house are pulling vacuum.

When I was living in Japan most homes and apartment had this system as a standard feature. The one I had in my apartment was made by Panasonic and was really small yet effective and was switching on automatically when necessary.

I really appreciate how you get more detailed than just the basics, Matt!

I installed this system in my house a few years ago and I can confirm that having the MAU is a massive improvement. The hood performance is much better than the higher cfm fan I had in my last house. I did have a problem with the outside air damper about 3 months after running this. I strongly recommend getting a higher quality actuator at some point. Other than that, this system has been great.

Really interesting! It's always fascinating when you encounter something counter-intuitive like the passive make up system! Different note: I went with induction about a year ago and have never looked back. It's so much better in pretty much every way and the air quality issue has become one of the top selling points for me... and it wasn't even a consideration when I bought it.

WOW. incredibly informative and very well demonstrated visually. This is a gold standard benchmark for KZfaqrs. Thank you for the fantastic explanation.

Just commented on your older video regarding make up air. LOVE this. This is definitely the route I'm going. Thanks Matt. See you next time ooooon the Build show.

What he doesn't point out is that this is only "easy and simple" to install when you have new construction and everything can be designed around it. Otherwise retrofitting such a system into most older homes can be difficult and very expensive. I got quotes anywhere from $12k-$15k to install an active makeup system in my house. Even passive systems were $5-6k

Loving the content at your house, my dream is to build my own one day and I would have never known all the building techniques and technology like I do now after watching your show for 3 years or so now, I can't wait for the day to come that I build my own yeti cooler house/monopoly house. Ive definitely learned a lot! Thanks so much Matt

You're so proud of your house, I love it. I could hear it in that laugh when you mention the backsplash. I hope to get my home fixed up that nicely one day lol. Your videos are an immense help.

Thanks for the info. There is so much information about sealing your home for energy efficiency but this is the first I've heard about Make Up Air.

As someone who takes cooking very, very seriously, to me, induction is the best choice for cooking in addition to the benefits Matt mentioned. The heat up times, searing power, etc are all superior to gas. It's just a better cooking experience. I have been using a miele that is very similar to the one Matt has (36" vs 42" but otherwise the same) for 4 years now and I'm never going back.

Someone needs to make a heat recovery ventilator for kitchen exhaust that can handle the grease. That's a lot of conditioned air to throw away.

Perfect timing on this video! I was just looking up make up air systems this morning

Great video on the topic Matt, your explanations align well with my experience with industrial ventilation and you answered some questions I’ve had about kitchen ventilation.

I had a house that was built in the 50's and when the adjacent family room fireplace was in use, I had to open the garden window over the kitchen sink to prevent the kitchen exhaust from pulling the smoke out of the fireplace and into the house.

Thank you Matt. Not enough people pay attention to fresh air vents and exhaust vents in air tight houses. Where's the moisture go is what people should ask when getting spray foam or other air tight systems.

From Canada have a 70's rancher that have been constantly/slowly upgrading and recently got to the point that if the dryer and range hood are both running at max it will occasionally snuff out the direct draft gas fireplace insert pilot. (Has thermocouple) So yes make it air tighter but don't forget to get your fresh air back in.

TY for the advice, I have been having smoke problems while cooking ever since we remodeled the kitchen with a new hood upgrade. Will have my HVAC guy take a look into this.

Great video. As an Hvac technician I’m blown away with how much knowledge you have on these common yet difficult issues to address. Keep up the great work and I really appreciate the in depth Hvac analysis on your videos!

Wouldn't it make more sense for the make-up air to come into the house at the cooktop? That way at least some of that make-up air would entrain the cooking smells and exhaust gas and immediately become exhaust gas, thus reducing the burden on your HVAC?

thanks Matt, I have always watched your video and learned a lot of things. I have diyed makeup air system with merv 13 filter box. It aotomatically turns on and off with ssr and current switch. Now I don't need to open any windows during cooking. thank you always from South Korea.

I built a house listening to this guy in San Antonio. I love when I meet another fan boy of matt! I have not installed this system yet. I just crack a window to let all the cedar in for my wife's allergies.

Hi. Great video that helps explain the negative pressures that are inadvertantly created inside a building. Whether a residence or a commercial restaurant. Often times I enter a restaurant and need to pull very hard to on the front door to overcome that "vacuum" in the building. As the door is opened I feel the wind blowing in. Or should I say "sucking in". Commercial kitchen exhaust often times include a fresh air (outside) air make up that is switched on with the exhaust. This unfortunately introduces cold or hot air (depending on the season) behind the chef's back and neck. Some systems incorporate precooling or heating of the ventilation air. This is expensive to operate and the result is that most chefs or building owners eventually shut off the fresh air make up and let the make up air get sucked in from every available location. Your reference to the 2018 IRC section 1503.6 (makeup air required) is definitely a consideration. Especially the delta pressure limit of 0.01 in w.c. BUT that section is prefaced with the condition of a dwelling containing gas, liquid, or solid fuel burning equip that is NOT equiped with powered draft ventilation. Namely, a naturally aspirated appliance that depends on a chimney with the quintessential barometric draft damper. Naturally aspirated appliances have been the known source of exphyxiation for decades. Many death investigations are attributed to this condition. So in addition to make up systems in buildings, a systematic conversion to power ventilated equipment is essential. Thanks

Hi Matt, when I design a range hood one of the most important things I find to have it work well is a capture area where the filters are at the top and you have the sides and front come down as much as possible this created a natural collection point for the heat and steam and the suction and filters work so much better. For make up air I put in a an outside make up air grill usually in the floor neat the cooking range hood this comes open when the hood fan is active with an air movement switch.

Excellent video on make up air. Congratulations on the new house. Inset cabinetry is a beautiful touch.

Great video, it was a topic I often think about when I turn on my exhaust fan. I usually crack open a window.

My concern is what you said: below freezing temps in MN and we sometimes cook fir 1 to 2 hrs on the range top. Summertime, easily 90 to 100F and humid as heck. Pulling 800 cfm inside the house would be gross!

The whole video all I could think about was the pre heater (from MA). Also where in the house does that vent dump into? Is it a busy corder or is is a quiet hallway? I am just imagining getting blasted by air. Great vid and great channel

Fantastic video, Matt! Great demo and very well-explained!

Great Video. I cant imagine the negative pressure during the holidays. Kitchen exhaust, Dryer, bathroom extractor fans running with a full house.

Hey, Matt! Thanks for that information. However, I don’t see links to the articles you mentioned that swayed you from gas to induction.

I just crack the nearest window or the slider. Free and works great!

Matt, this is a great conclusion to the entire point of an envelope properly breathing on our own terms!

Great job! Wish I could go as far as you did. $$$. Tightened up our 1980 house, but was told to go no further unless spend a lot more on HVAC. A lot of our make up air actually comes from the wood stove we tend to only use in power outage or severe cold. If we use the wood stove, a window is always left open. Not enough leakage in our house.

Your 400CFM exhaust is only with an accompanying Static Pressure, just like a HVAC blower has a 12"x18" output but needs a 24"x24" passive input to move the rated CFM (1500 in this case).

Matt learn how your equipment works. The yellow tube is to the B Channel that tells the DM32 the pressure differential across the Fan (as selected by the user). The red tube is for the pressure differential inside to outside (A Channel). The reference for the inside is the adjacent Blue tube connection. I have done over 2500 Blower Door Tests in 4 years. Remember the accuracy of the DM32 manometers is in the tenths of pascals. From what I have read positive pressure inside is preferred over negative pressure. I don't understand why you chose a separate makeup air system instead of using your air exchange system for the makeup air. Other brands of air exchange systems regulate airflow using pressure differential. You added a separate system with additional cost and maintenance. I love the induction, but it is treated as technology. It is not considered repairable. So when one of those diodes dies in the hob the hob is useless. That means you are spending thousands to replace your cooktop every 3-5 years over a failed $5 part (and landfilling the old cooktop). You can still get replacement nichrome elements (70+ year old tech) for coil cooktops today. We're currently waiting on China to deliver our next generation of induction cooktops with very short life expectancies. Tell me how filling landfills to enrich the CCP (and associated USA importers) with glass and computer parts is environmentally friendly.

Exactly the video that I was wanting to see. Thanks!

Very informative. Have relied on passive make-up venting in the past. Will try to avoid it now.

Yep, seen plenty of kitchen remodels with a powerful 1000+ cfm commercial hood over their 6+ burner commercial gas range and zero consideration for makeup air. If they have other natural draft combustion water heaters, furnaces, boilers or chimneys, that big fan will try to pull combustion appliance/fireplace gasses back into the house. Problems like THIS is one way to have a very deadly carbon monoxide problem. I've seen the plastic fittings coming up out of the tops of water heaters melted from the hot gas getting pulled out of the side of the flue gap.

Matt - I would love to see that link to the articles that convinced you to go induction vs gas cooktop. Also would like to hear why you chose this make up air system vs a system that provides the make up air around the perimeter of the hood. And as always - thanks for the great content.

another great video! Keep up the great informational videos! We appreciate them!

Great job Matt as many contractors m8ss this.. I think you need to study on the energy effectiveness of this though. As others have pointed out replacement air should be conditioned. There are so many sources of exhaust fans in a home (bathrooms, laundry room, etc) that a cost effective solution needs to be part of the HVAC system and introduced near the exhaust locations.

@Matt Can you share those reference documents of why you chose an induction stove?

Matt, Question what about humidity when sucking the out side air in, We know how hot and humid it gets in Texas. seem to be a lot air air flow quickly..

Awesome, I especially loved the remote fan too...

I did testing of commercial cooking hoods, and we used to bring in the make up air right around the perimeter of the hood, to create a Venturi effect. We then wired in the makeup unit ( which supplied conditioned outside air ( heated or cooled). Bringing in the makeup air right at the hood also eliminates having a draft between the makeup air and the hood.

I can now see why my 900cfm exhaust fan only works when I open the window on another side of the house

Is the makeup system also tuned to your bathroom exhaust??

Great video Matt! I shudder to think what a powered extraction and active adder costs to exhaust food odors but I can clearly see that's the way to go when/if budget permits

Great video. Congratulations on finishing your home!

Cool visualization. I wonder if this could somehow combine with the ERV. And yes, if I were building or remodeling, I would definitely go with an induction cook top. In a more difficult climate, it might even be better to just filter rather than exhaust.

Thanks for the walkthrough. A little unfortunate that it’s going to be exhausting primarily conditioned air through the exhaust vs having the makeup air drop closer to the exhaust. I hope its not noisy or drafty in the family room when you’re entertaining/watching TV while someone is cooking.

Well done sir. This topic is so often skipped and so critical. No perfect solution (I know of) without compromise of added cost (mechanical solutions) and perfect control of conditioned incoming air (this is all unconditioned air coming in). But thankfully we don’t cook all day! Would love to see how your indoor experience compares to these first cost concerns over time!

Great Video, One thing to remember is Carbon Monoxide Poisoning from Gas Appliances. That is why Make Up air is so important. In Commercial Restaurants they require a separate vent and duct work going in the opposite direction of the Exhaust vent.

I’m surprised you didn’t run the incoming air thru your ERV. Seems like that system would allow a lot of warm moist air to come flooding into your home in the summer.

I've noticed that we even have to use the exhaust fan when using an air fryer. Otherwise within a few minutes the whole house will stink.

This is a big area where commercial kitchens have a clear lead. The hoods are much bigger, allowing for a larger capture area. Makeup air matches the required exhaust rate and either comes down directly in front of the hood or slowly passes through the kitchen from the opposite side allowing for better fume capture. Sometimes the air coming down in front of the hood is cooled to keep the cooks comfortable. Or, with the latest tech, all of the air is cooled or heated to keep the whole kitchen comfortable.

Thanks for this video. I've seen your other video on this, but this is more in depth.

I wonder if anyone has used a ventilating dehumidifier relay to activate when needing make-up air. That would be cool.

So the 500-lb elephant in the far corner of that room is: WHAT HAPPENS when that "powered make-up air device" fails? Is there a feedback loop to the exhaust fan that prevents it from turning on? If not, it would seem the "risk" of back-drafting any combustion appliances would immediately return, but be "undetected"........and potentially start pulling in Carbon Monoxide from various sources. This would seem like a big advantage to using a "passive solution", rather than a "powered" solution. Electro-mechanical solutions ALWAYS fail eventually.................well-designed passive solutions, not so much.

Great demonstration Matt. You are as good of a teacher as you are a builder. BTW, I’ve been on the fence about induction but your recommendation gets me off that fence.

Thank you for sharing, enjoy your newly designed home

I'm sure someone corrected the comment that a passive solution would need to be 16 or 24 inches. An 8" diameter has approx 50 square inches. An 11.5 inch diameter has roughly 100 square inches.

Do you have any combustion appliances? If you are 100% electric does the difference in air pressure even matter?

Beautiful mechanical system! It’s so important to having a long lasting comfortable home

We ran into this a lot in central Florida … when they started building home too tight we had to introduce fresh air. The problem is just pulling in outside air at 96 degrees and 99% rh caused a huge issue so instead of installing a 3500 kit from Trane I wired the damper to the compressor circuit and ducted it straight into the return air box now I’m watching this and I’m wondering how I could do something similar to the exhaust I don’t live in Florida now but in a more forgiving climate but I like the concept good job Matt ….oh we call that a magnahelic to measure those air pressures a manometer we use to measure gas pressures like propane or natural gas

A passive system can't work at all to achieve "0" differential.. It requires a pressure differential to merely suck replacement air in through the passive hole.. No pressure differential = no flow.

What is a bit confusing is all of the negative pressures (kitchen hood, bathroom vents, dryer vent, etc.) have to be balanced and ideally run thru an hrv. But only certain exhausts can be run thru an hrv, so how do you manage it. A comprehensive treatment of air pressure would be helpful.

EXCELLENT explanation. Thank you.

This guy has brought building to a whole new level.

Ideally, I want an heat exchange between the inbound and outbound air.

Is it air while the wife puts on her makeup?

Excellent video! Loved the experiments.

Nice video. I used to be a mechanical engineer specializing in HVAC systems (not anymore though). I learned some new things from your video. It might be nice if they could use a heat exchanger so that the makeup air could be heated in the winter or cooled in the summer by the exhaust air. I'm sure they have a good reason for not doing it though. The exhaust air might have a lot of grease in it that could foul it up.

You never really explained why it's needed besides code. Who cares if the pressure shifts? Edit: why the code exists was answered below.

Just had my 40+ year old house renovated with new window, roofing & siding. All of a sudden my CO detectors started going off on a regular basis. Due to the house being so much tighter, it was sucking in utility exhaust fumes. I installed a makeup air duct direct from the outside to the suction side of my forced air gas furnace. Now makeup air automatically gets sucked in under power whenever the furnace kicks in. Huge difference! The kitchen is all electric and I don't do alot of cooking, so little makeup air needed there. My utility bills have not shown any measurable increase since setting up this system.

As always great information, ventilation is not the same as circulation. Make up air is very important!! 400cfm's is roughly about 1 ton of air. 800-2,1200-3,nd so on.Another good point no more than 3pascals of difference in air ventilation. Lots of good stuff to know from "THE BUILD SHOW" Thank you Matt!!!

Very cool. Love your demo.

Here in Utah we have been installing make up air in homes for the past 15 years. It was if the range vent is more then 400 cfm. The only range vent that has a built in relay is Bosch all others we have had to use pressure switch relays to activate the make up air. That way when the range come on so does the make up air.

Good video Matt, lots of good questions, but does bring up and important point that the system has to be engineered properly.

Previous owner of my house "renovated" kitchen and ran hood fan exhaust duct to the chimney stack. The house is 3 story high so chimney is quite high with kitchen on the first floor. So when fan is on, all cooking air/smells pushed into the basement (through chimney cleanout)..

Great videos Matt! Learning a lot as I'm in the process of a new home construction as well. I've been thinkitng about this make up air system for a while and was hoping I could find a way to trigger the Aprilaire ventilating dehumidifier for the ventilation mode when fans are running. From a home automation perspective there are several ways I can determine when fans are running and the cumulative CFM draw down on the house, however, while the Aprilaire ventilating dehumidifier pairs nice with the HVAC and Ecobee for humidity control all I've been able to determine (including speaking with some very knowledgable folks in Aprilaire tech support) is that the ventilation feature runs on a simple minutes of air per day controller and can't be triggered by any external protocol or relay. I'd be really interested if anyone has gone down this path and figured out a way to do it. The Fan-Tech stuff looks like it might accept external triggers which I'll pursue but I'd like to use the upgrades I've already committed to instead of buying more equipment. Plus the ventilating featon ure on the Aprilarie already has a filter and dehumification capability which for a Florida home would be nicer than just bringing in hot humid air to balance the kitchen and other fans.