Make Up Air for a Kitchen Exhaust - Most Homes Suck. (Pun intended)

[@brantmacga]

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.

[@ethelryan257]

Wyoming electrician, here. Same problem.

[@rasichap]

Most GC's are not well informed on building science, let alone homeowners. It's a tough sell when it comes to ventilation. The construction industry is notoriously slow to adapt and tighter building envelopes are still a relatively new requirement. It's going to take a while .

[@joseepena8553]

That's why every restaurant has make up air....common sense???

[@pandagold4722]

@@joseepena8553 Not so common...

[@flinch622]

Yes: crack is the operative word. Mention to them that with proper make up air... they can prevent a bunch of air conditioning/heating dollars from being sucked out of the house.

[@helmanfrow]

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.

[@-JonnyBoy-]

He said double or triple the size not area...

[@TurdyMcTurdface]

​@@-JonnyBoy-flow area is what matters. The original post is correct.

[@zimmermanlandscape9287]

lol

[@ddjohnson9717]

yeah. areas are weird lol.

[@brittcrowell]

@@ddjohnson9717 Yea, math is hard for most of you I guess.

[@ColeSpolaric]

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.

[@renniexedis3459]

I think your right

[@renniexedis3459]

We do the same for chimney fresh air fire place

[@JsGarage]

One of his older videos kzbin.info/www/bejne/farTmWpolN5rrbM

[@mrgylex123]

humid or super cold unconditioned air...im not a fan of this (pun intended). Im surprised Matt didnt leverage the Panasonic Intellibalance engineers. Their newer model ERVs allow for a remote boost that can pull in air to compensate for fans like the kitchen. Tha >400CFM can basically negate any effectiveness you're creating from running an ERV

[@peterbarreca1568]

Matt you rock. Great video!! None of this is covered by codes in Australia but fresh air intake and no negative internal pressure is important for a healthy house. I have a computer controlled system in my roof that can bring air in or exhaust it The air comes thru a roof vent controlled by dampers It is less of a problem bec our climate is milder and the wall cavity is open to the roof cavity PeterB

[@19D48D3]

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.

[@Ty_N_KC]

Where are ya located???

[@19D48D3]

@@Ty_N_KC Europe right now.

[@9873459872134234]

which is practically never done correctly, which why U.S. DOD is switching everything over to non-toxic, non-lead ammo (M855A1 Enhanced Performance Round, etc.)

[@19D48D3]

@@9873459872134234 dOD found out a few decades ago that using and abusing training facilities will lead to losing them. Things like physical damage to the land as well as things like lead in the ground water. The remediation needed to repair damage is more expensive than finding new ways of training. Things like the EPR are a benefit of that new way. With lead only being used by pistols the maintenance costs have dropped significantly on the indoor ranges.

[@TheSnekkerShow]

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.

[@dougw3436]

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.

[@CopeBUILT]

He mentions that at 3:47

[@eliinthewolverinestate6729]

Rockwool then spray foam around a chimney will keep chimney from condensing moisture.

[@cmeyer1]

You can't wake up dead. Functioning CO detectors prevent that...

[@stipcrane]

I haven't built a house capable of backdrafting for 25 years, and backdrafting CO is essentially to concern of the IRC. Furnaces, fireplaces, and water heaters today are all sealed combustion/direct vent. IRC M1503.6 Makeup Air Required - "Where one or more gas, liquid or solid fuel-burning appliance that is neither direct-vent nor uses a mechanical draft venting system is located within a dwelling unit's air barrier, each exhaust system capable of exhausting in excess of 400 cubic feet per minute shall be mechanically or passively provided with makeup air at a rate approximately equal to the exhaust air rate." I couldn't find any code language specifying under 3 Paschals. I wondered why my local inspector never asked about the size of my range hoods, and I guess this must have been his reason. I have a buddy who disabled the 3rd button on his 600 cfm hood just for fear of a failed inspection. In Seattle I had an inspector jump all over me for a 1200 cfm blower not having makeup air, yet we had zero atmospherically vented appliances. For that volume, I would agree that if anyone actually ran it on high makeup air would be desirable.

[@ceedeeb]

He died from death

[@ethelryan257]

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?

[@jasonjmusic7542]

If an 8" diameter duct isn't enough, a duct with 3X the flow area is 13.86" in diameter. To calculate that you take the square root of 3 x 8^2. A 24" diameter intake duct would have a 9:1 flow area ratio vs an 8" diameter exhaust duct. To calculate that it's (24^2)/(8^2) = 9. Pi drops out of these calculations because constants common to both sides of a ratio cancel each other out. That being said, I'm curious to know what your recommendation is for the diameter of a passive make up air duct for a range hood with an 8" diameter exhaust.

[@drivewayy]

​@@jasonjmusic7542 ....right? He was so close after he made the reading drop with the 2nd hole. He should made a 3rd and shown us the meters results.

[@jackknife89actual]

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.

[@davidwatkins8016]

Thanks for your input on this question. Is the stack effect a "chimney" effect at the stair? Is there enough leakage of air at the top of these staircase "chimneys" to make a difference?

[@michaelminasian4891]

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.

[@TwilightxKnight13]

You have lost your mind. Anyone who takes cooking seriously would NEVER take electric/induction cooktops over gas.

[@sunspot42]

@@TwilightxKnight13 I got a cheap plug in induction burner two years ago and haven’t used my gas stove since. Once you get used to its kinks you’ll never want to deal with gas again. And a full 240V stove version with a larger coil would be like driving a Cadillac compared to my little plug in Yugo.

[@neilbennett9281]

No one ever goes back. Induction and gas have an inverse efficiency i.e. 75/25 % V 35/65 % BTU energy consumption. I’m a pro chef and now hate gas. At least open flames have a bit of romance.

[@CrispinCourtenay]

For me--California--to reach the same BTUs (25,000) on the main burner, 100,000 at full tilt, I would need a commercial induction cooktop, run 60A to the kitchen and install a second electric service. That is at least $60,000 in expenses. Just not worth it. I am a former chef, and have used induction, heat is heat, but I like using gas better.

[@sunspot42]

@@CrispinCourtenay How many of those BTUs from gas actually make it into the pan, though? From what I've read, only about 40%, especially running flat out. The rest just heats up the room. Which isn't something typically needed in California, unless you're up at Tahoe or something.

[@coldfinger459sub0]

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.

[@goodselections]

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.

[@mcintosh.daughter]

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

[@TwilightxKnight13]

That’ll be the day when I see residential building inspectors testing differential pressure. Hahaha

[@stevenle1760]

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.

[@FJB2020]

How about if you only cook with cast iron?

[@e3a3c3]

@@FJB2020 Cast iron works with induction, but it's sometimes rough and may scratch the glass surface.

[@ctrlaltdebug]

Gas is the best. I can still cook when the power is out.

[@trevorkolmatycki4042]

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.

[@acjohnson55]

Does this exist?? If not, why not?

[@drunkenmessiah]

A product like you describe exists, but it is not an ERV/HRV and should not be. ERV/HRV are balanced systems that are designed to push out exactly the same amount of air as they pull in. They are very poorly suited to compensating for pressure imbalances in a house. AirScape makes a slick, dedicated make-up air unit that does just what you say: it monitors static pressure inside and outside the house and runs an electronic variable-speed fan to keep the house balanced. Has a nice, heavy-duty damper that shuts tight when not in use to prevent energy loss. Since it is pressure-sensing it does not need to 'communicate' with all the various bathroom fans, hood vent, etc the way older super-complex commercial style MUA systems do. This makes it dead simple to set up and really flexible in its functionality. Has very high max flow, 1600CFM, so can be used for neat tricks besides MUA such as whole house ventilation or scavenging excess heat from an attic space (intake is well filtered so no air quality concerns). We've found it cheaper and more flexible to use separate ERV and MUA units rather than trying to use some fancy all-in-one system (they exist but are $XX,XXX, whearas the MUA and ERV unit we use costs ~$3000 combined).

[@drunkenmessiah]

@@acjohnson55 It does, kinda, but is not an ERV/HRV. See my response to OP.

[@acjohnson55]

@@drunkenmessiah I checked out the Airscape, and it looks pretty cool. But could you explain why it would be so bad to run an HRV unbalanced, other than that it is intended to be balanced? What harm would result, if, say, you ran it with a little extra intake to stop drafts from a negative pressure situation?

[@drunkenmessiah]

There's a lot of issues that make your suggestion less than ideal. The energy recovery mechanism of an ERV depends on on that balanced airflow, so much of the benefit of having one goes away if you run it unbalanced. A typical ERV will not support the sheer air volume needed to compensate for a kitchen hood vent (400+ CFM). Typical ERVs don't actually filter the incoming fresh air and are dependent on the central air system for filtration. What it boils down to is that if a manufacturer made an ERV that does what you describe it'd be more expensive than having separate ERV and MUA units. It is possible to make a super sophisticated ERV that does all the things you say and, indeed, there are commercial solutions just like that. However, they cost well into the five-figure range and are therefore unsuitable for a conventional sub-$500k home build.

[@BenjaminSahlstrom]

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

[@rayRay-pw6gz]

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.

[@edhoward7566]

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.

[@peep39]

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.

[@nicks7042]

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

[@KRM849]

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.

[@tommanley2924]

The weak link are the actuators.

[@Seedavis397]

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!

[@chiplawrence7178]

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.

[@stevenhaas9622]

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

[@billm1651]

Most older homes are so full of leaks its not needed.

[@snowgorilla9789]

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.

[@eliinthewolverinestate6729]

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.

[@Erick-di9gm]

Turns to mold.

[@BretClements]

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!

[@MichaelCouvillion]

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?

[@YoutubeTM432]

This is how ive seen it set up in restaurants.. the make up air will sometimes be on the floor at the foot of the oven, pointed upwards..

[@sparkyoc6766]

Sounds right to me. Matt, why have that 'draught' running right across your living area rather than having the make up vent nearer the cook top and localising that air exchange?

[@gearbear1993]

Hes talked about this in a past episode. This was just the way that worked out best for his floor plan, and distancing from the exaust point. If he had a basement type foundation it would of allowed for more options

[@qwerty112311]

@@sparkyoc6766 it’s not like the only air that can exhaust is the makeup air coming in. The cross section of the space between the two is enormous, so it isn’t as though there will be a laser beam of fast moving air across the entire living area.

[@RisingTidesAtlas]

Yeah. Matt actually has a video about that and does.it that way

[@Malikar001]

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

[@bigdaddio1959]

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.

[@sebastiantevel898]

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.

[@brettster3331]

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.

[@OnlyOneFever]

Hi Brett. I've got a 600 cfm hood and open a door. This video inspired me to install makeup air. When you're coming in via the floor, are you going under the kitchen cabinets with a grill in the toe kick? It's the idea I'm getting for my kitchen. Thinking near the range too. Thanks. Mike

[@brettster3331]

@@OnlyOneFever Hi Mike, I try to get as close to the range as possible with the make up air grill, and with a 600 cfm hood going into the toe kick space should be fine it depends on how tight your home is, I on designing usually put the make up air under electric ranges or dual fuel and just close not under all gas ranges. I am a big fan of the look and ergonomics of ranges verses a separate cook top and oven. I have been in many homes with the cooktop with a hood is in a separate area from the oven without a hood and any smells from the oven fill the house sometimes with smoke.

[@brettster3331]

Hi Mike, I forgot to say with the make up air coming in close to the hood a lot or most of the air being sucked out by the hood is coming in from the outside so it does not need to be cooled or heated and has a much smaller impact on home energy use, you can use the hood as much as you need to without feeling like you are wasting energy dollars.

[@OnlyOneFever]

@@brettster3331 Thanks! Good point on the makeup air being located close to the range. Now I'm thinking of putting the air grill directly under the freestanding range. Create a nice flow going from floor and around the range, straight up to the hood.

[@OnlyOneFever]

@@brettster3331 I don't feel like the house is "that" tight, but if the door to the garage (near the kitchen) happens to be ajar, the hood draft will pull it open a bit. We still open a window and the door to the outside regardless. Especially when searing meat. Thanks again

[@shulmice]

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.

[@Bryan46162]

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.

[@ericpeysar2593]

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

[@publicmail2]

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).

[@klg642002]

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.

[@zjeepgozweeln]

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.

[@markbennett1237]

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.

[@DavidZwarych]

An HRV...or ERV on make up air to reduce heating, cooling and humidity. Cooktop vent 400cfm is just one source. Run the clothes dryer, all bathroom fans, and all fuel burning appliances/ fireplaces at the same time - THEN measure total cfm and pressure differential. Too much work and cost? Open a window, turn on AC/heat, humidifer, filter. Still too much work and cost? Cook, shower, and dry clothes outside. Good luck.

[@chenglo8999]

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!

[@jheiss]

That air is coming into your house anyway, without an explicit makeup air system you're just pulling it through gaps in your doors and windows.

[@MrPhys]

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.

[@mattv5281]

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.

[@jon8864]

My house has a HRV but the rangehood isn't connected to it, it filters smoke and smells out of the air and blows it back into the room (called a recirculation rangehood where I am). This is commom practice for airtight houses (mine got 0.4 air changes on the final blower door test). I'm not sure if it''s the grease, moisture, the airflow or all. My $7000 HRV does 150 m3/h on high (normally runs at 50) and my range hood does 800 m3/h, so even if it could handle the grease I'd have to buy one 5 times bigger than I need without it. I imagine the air being exhausted ins't heeated much at all by cooking, but if it is that could also be a problem.

[@christophergruenwald5054]

@@jon8864 you definitely over paid for your HRV. I have a massive dual core fantech and it cost me around $2000 to install myself including the ducting and timers to service 4 bathrooms.

[@steveedlund7357]

Doing the same on my build this year with 2full and 2 half baths with a EVR. What CFM unit did youuse?

[@sparksmcgee6641]

@@christophergruenwald5054 I get that doing it yourself is cheaper and I don't like to talk bad about a person thats happy with a HRV install but that does sound pricey. A lot of ducting affecting trim and other things could run it that high. High cost trim? 4 vents that need a plaster touch up then blend paint could cost a 1000 just on the holes. Just commenting to give folks context. A good fantec for 80 percent of US homes retails for about 2-2500.

[@jon8864]

@@christophergruenwald5054 look up the efficiency of your fantech and compare it to zehnder, I d never have fifteen passive house certification with a cheap HRV. I think you should look up some numbers every now and then, quirk out what's what.

[@nathanslator7812]

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

[@infiniteadam7352]

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

[@jimmyphilip2340]

Are you in NC by any chance?

[@squeekhobby4571]

Same here

[@jamesortolano3983]

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!!!

[@johnwhite2576]

james for sure 3 or less highly desirable, but has anyone really died from temporary 5 pascal negative pressure in a house while cooking ?? really hard to make he case for they expensive, complicated Fantech system

[@thomasleahy3767]

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

[@stuarthkrantz]

I bought a make up air system from HVACQuick in Oregon. I haven't finished installing it yet Still figuring it out. I have a heater. It's the last piece. Once I saw Matt's video - I don't remember which one - since our home was done, I put the make up air system in the basement and opened a hole underneath the Kitchen Cabinets which are next to the microwave. I put a vent on the front of the bottom of the cabinet in front of the hole. I'm hoping it works as well as Matt's does from across his home.

[@TrustworthyExpert]

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.

[@stevenhildreth5784]

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

[@zachpw]

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.

[@TD-zc4zi]

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.

[@donaldlee6760]

I was also thinking it would be more efficient to have the makeup air released next to the stove so that the home's conditioned air is not wasted.

[@bradkastephens]

yes it would be better to have the make up air in the range hood, as normal commercial range hoods work

[@steveedlund7357]

Yes, but - because, in Matt's case being in Austin, the MUA isn't cooled. That would be very expensive because they are custom units with very thick evaporator coils with a high pressure drop and the fan would need to be upsized. S, if you place the MUA grills close to the stove, the cook will need a shower from sweating. It's best to dump the MUA to a conditioned space allowing it to mix with conditioned air and let your primary a/c handle the load. And yes, your ducting and supply grills should be sized for a 500fpm velocity to avoid noise, even if it requires 3 grills to avoid the noise problem.

[@art_bat]

In Europe (Spain) most homes use induction and, in passive houses, recirculation extraction hoods. That ensures that there aren't combustion gases or smells, while keeping air tightness and thermal performance, since all air is controlled by the heat exchanger. Direct exhaust outside the house's envelope would be considered a mistake in terms of energy usage. The downside is that these hoods require more frecuent maintenance (filter replacement or cleaning) depending on model.

[@steveedlund7357]

In commercial exhaust hood we see horrible grease buildup which can lead to fires. How do you keep this under control with a recirculation system?

[@art_bat]

They use several filters. A first physical barrier with easy access (greases) and a 2nd or 3rd barrier to filter smells (carbon activated, that needs replacement, or ceramic, that regenerates in the oven). To a given degree, grease build up will always be an issue, recirculating or not 🤷‍♂️

[@art_bat]

Available here there exist such products from Bosch, Elica and Neff, at least.

[@derf_the_mule1405]

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.

[@hoondaily270]

Based

[@rcpmac]

Considering the cost of conditioning outside air distributed throughout the house, a zonal makeup air solution in the kitchen would be preferable. Interesting comment on induction cooktops.

[@gone2island819]

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.

[@corgarcia7381]

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.

[@frostman9661]

Induction is better than gas in almost every way, especially health wise. The only downside is getting used to cooking with it. But I agree with the makeup air being around the perimeter of the hood! I wonder how you would do it/if it would work just as well.

[@turboflush]

Induction is special. Plan on tossing pans in garbage. Proper pans will heat very quick. Even pans that say they are compatible.. May not be fully efficient.

[@steezydan8543]

Choosing against gas stoves and gas heating is pretty easy, gas leaves harmful particulates in the air that negatively impact your health and there is a much larger risk of fire/explosion compared to any of the other options. An inductive element vs a resistive element is a lot more nuanced, induction is faster and more efficient but it requires a ferro-magnetic pan to use, is extremely resistant to filth and is easy to clean but expensive, whereas a straight up hot plate can be used with almost anything, is less efficient than induction but massively more efficient than gas or fire, and the tech behind it is so simple that it's the least expensive option by far.

[@cruzmissile25]

Last i checked, professional cooks don't use induction cook tops. Unless you have an extremely level flat pan, you will get un even heat points.

[@turboflush]

@@cruzmissile25 Never had a problem with uneven heat. Pan quality matters. Cooks use what they are given. They dont necessarily get to choose the appliance.

[@pandagold4722]

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

[@scottperry8388]

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.

[@robbarmstrong1342]

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.

[@jon3615]

Pi R squared is also a useful equation for comparing pizza prices. Usually the largest pizza is the most pizza to dollar ratio.

[@zacheriashelm]

He didn't say anything about square. He talking about the size of hole. Not the square of it

[@jon3615]

@@zacheriashelm Pi (3.14) multiplied by the radius of the circle squared (exponent of 2) is the calculation used to find the area of a circle. Doubling the diameter of a circle more than doubles the area. When I said squared I was not talking about perpendicularly or the shape I was using it as a function in math.

[@rodgraff1782]

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.

[@toddjones1403]

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

[@patrickdougherty2777]

For you, good. In Minnesota this winter when we had 20 degrees below 0, not good. Matt did say that in Minnesota you might want to install a preheater to the makeup air.

[@mamabear9389]

That is what we do too. We also skipped the range hood and just put lids on our pots.

[@mtacoustic1]

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.

[@sunspot42]

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.

[@steven7650]

You can't the exhausted air from cooking is full of grease, food particulate, and maybe soot the recovery membrane would clog up.

[@YoutubeTM432]

400 cfs is a lot of flow to run thru an erv

[@jpe1]

@Ross Outdoors yeah, but the ERV gets its E (energy) from the air getting exhausted to the outside; there ain’t no free lunch, the E has to come from somewhere.

[@sunspot42]

@@jpe1 Good point.

[@gadget13]

Short of running it through the EVR you can actually install the heater in correctly he states that he’s in Texas and he doesn’t need the heater actually you do it will take and dry out the humid air and leave it just a little warmer but it will be much drier and then run it into the HVAC system which will then chill it down and dump it back in

[@jessmasterflex1]

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!

[@panchitox8875]

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.

[@jeffeverde1]

And hidden in the ceiling, no less. An indicator light for the return system, mounted on the vent hood control panel would be a big plus

[@ThatEEguy2818]

If you think about it, it makes sense that with an 8" passive hole, there is such a pressure difference. If there wasn't a pressure difference, the air wouldn't be pushed in through the hole. Since the exhaust vent is pushing so much air out, there has to be enough pressure difference so that the air is made up. It reaches equilibrium.

[@scorpio6587]

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.

[@sparksmcgee6641]

I would recommend a technology like Ventahood for that. It doesn't need filters and no one keeps on top of filter cleaning. Former commercial kitchen cleaner here. : )

[@andrewdelapp]

Agreed. Hopefully fantech can add capability to their ERV's to ramp up air intake air when the range vent is on. No extra holes. Whereas with Matt's make up air solution, in the summer he is bringing in hot humid make up air that probably isnt feasible to cool at the make up air unit.

[@sparksmcgee6641]

@@andrewdelapp It would double the price of the HRV. Most of them have a boost mode for things like that and it's just a low voltage wire so it could be mounted in a drawer, All the HRV ducting and extra cost wouldn't have a pay off for the small amount of air in the oven vent. Maybe it's venting 10 to 30 minutes of furnace operation a year worth of heat. A carbon filter system to recirculate the air would cost more than the make up air.

[@scorpio6587]

@@sparksmcgee6641 I checked out Ventahood. Looks great. Thanks!

[@sparksmcgee6641]

@@scorpio6587 they're pricy. Look at replacement parts. buy the motor, fan and grease trap are the parts that make the magic happen. If you're a DIY that's the way to go. maybe 5-600 bucks. If you're a contractor get the hood that you can mount you're own finish to, like a cabinet face ready refrigerator. I think they start at1500-200 for the basic stainless hood.

[@flinch622]

A clue on duct sizing for folks remodeling... look at any industrial centrifugal pump: inlet is typically larger than discharge side. The reason is a little different [preventing cavitation] but the principle with air functions about the same. Atmosperic pressure is roughly 100k pascals - that's your precharge to the inlet. Output pressure off a fan is an amplification of that - never equal/always more:. So, if in/out ducts are equal size, the fan will take volume from somewhere else trying to reach its design output.

[@jimmysquires5093]

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

[@sparksmcgee6641]

Hrv will cover that

[@vrdrew63]

Excellent material on a topic not very well understood by most homeowners. Some things to consider: 1) Energy efficiency. If you are pumping 1000 cfm of conditioned, humidified, and filtered air out of your house, and replacing it with outside air that is significantly hotter/cooler/drier/wetter, then your HVAC system is going to have to do some work to maintain a comfortable living environment. A 3000 sq. ft. home, running a 1000 CFM extraction system, is theoretically going to exchange 100% of the inside air for outside air in a little more than 20 minutes. That's going to cost some amount of money in either heating or air-conditioning running costs. You can reduce this, potentially significantly, by utilising a heat-exchanger where the warmed/cooled inside air is used to condition the incoming make-up air. But these systems add complexity and cost. And you need to have the space and ducting routes to utilise them. 2) Speaking of which....The reality is that considerably less than 100% of our housing stock can use outside air extraction. In many instances people live in multi-unit apartments, condominiums, or other structures that simply do not offer a clear route from cooktop hood to the outside. And even in single-family houses, we need to remember that there are practical limits on the length of ducting (and number of turns) between hood and extraction port. 3) Another alternative, which doesn't rely on makeup air, is a recirculating system. Rather than venting cooking smoke/smells to the outside, instead it relies on a series of filters. These filters comprise washable aluminium mesh grease filters, and replaceable activated charcoal filters to deal with smoke and smells. While less-than-optimal these systems do a pretty good job of removing cooking nasties from the indoor air environment. And without the energy losses of a vented system. Overall, my recommendation is to use a holistic approach to dealing with cooking ventilation. Take into consideration the climate you live in. If it's 72F and 50% humidity outside, then maybe its not such a bad idea to let outside air into your house. If those numbers are considerably hotter/colder/wetter/drier - recognise that conditioning the air is going to come at some cost. And maybe think about cooking particularly smoky dishes outside, on the barbecue, if you have that option.

[@dansklenicka8403]

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..

[@antibodyarmy]

you could use a HRV/ERV in place of a in/out vent like this, that will help reduce indoor humidity and/or you can localize your makeup air to near your cook tops to to create a updraft that will both supplement the air and not cause a massive rise of humidity during the humid times of years. this is what commercial kitchens do to keep smells/humidity down inside the restaurant. Its also why you smell doughnuts when driving by a bakery or french fries when you drive by a burger joint, smell some good cookin' so you stop by :P all while not overwhelming customers with food stank when they are inside.

[@dansklenicka8403]

@@antibodyarmy Good Info thanks for the reply!

[@Whodafuqcareswyt]

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

[@neilbaunsgard8106]

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

[@s9josh778]

They are way more efficient- and cool to the touch much faster (aka, safer). The world is converting.

[@justinoverstreet1119]

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.

[@davidhoover2446]

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

[@Floridaman8783]

Yes. Do it in the builds we do the hvac on in S Florida all the time b/c the incoming air is so gnarly humid and hot.

[@gadget13]

There is a Fantec system called an energy recovery system that does just that. It is basically a heat pump that works both ways. Instead of just pulling humid outside air in, this put in-line for the makeup air and as Hot humid outside air comes in to the system it pulls energy out of the cool indoor air applies it and removes humidity from that air coming in and dumps cooler air into the space in the winter it does the reverse

[@GlenS123]

Great basic video, there is a 3rd option. Vent hood with make-up air entering at the hood. Doesn't mix with house air so doesn't have to be heated/cooled. Down side, very expensive, typically custom.

[@edwardsmith3062]

What’s odd to me is that this is a separate system from his zender fresh air system. Isn’t this a somewhat crude duplication of a functionality he already has (meaning can’t using his range fan make a call to the zender to import an equivalent quantity of fresh air throughout his home?)

[@johnwhite2576]

@@edwardsmith3062 my understanding is slender ia always balanced, dont have the ability to create negative or positive pressure OR sporadically as called for , have different amounts fo air drawer into and out fo the house (go figure war what a 10k plus system ? LOL

[@jesinbeverly]

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.

[@mtscott]

Most passive ventilation systems are balanced. Ie they suck and blow similar amounts. Once you create a differential (due to blowing out more air from the hood) the the passive system should make it up due to the differential. Ie.lower pressure inside means more flow from the suck side. Just simple physics. Was the passive ventilation off in this video?

[@powdernate]

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.

[@vespafish]

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

[@josephsweeney4219]

great question

[@JG-el5tb]

Even without combustion appliances pressurization or depressurization has the potential to cause issues, particularly where there is greater temperature differential between the interior and exterior. Having positive pressure could force the air from inside your house out through even the tiniest of openings in your envelope where it could condense and deposit moisture potentially causing mould issues. Negative pressure inside the home could suck air in from outside with the same potential to condense.

[@rasichap]

@@JG-el5tb Good answer!

[@xcSTRIKERxc]

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

[@IvanRossS]

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

[@jon8864]

which is the cheap and reliable option

[@IvanRossS]

@@jon8864 yes I paid only $300 for my hood vent.

[@PanaLumberjack]

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

[@gsadow]

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.

[@featherboards1565]

I'm curious about this as well.

[@steveedlund7357]

ERV's and HRV's cannot be used as makes up because they are a balances system. Fantech has a pressure controller that monitors building pressure so that if any exhaust creates a negative pressure in the house the MUA energizes to equalize the pressure inside the house relative to the outside. It's a more expensive controller because of the very low pressures it senses, but I've used them in commercial buildings for a very long time.

[@gsadow]

@@steveedlund7357 Thanks for your input. Is this MUA usually run thru any conditioning such as a filter, heating/cooling, humidification, or just commando direct into the house. It seems crazy to spend so much effort to seal up a PassivHaus and then have all this MUA kind of defeating the purpose.

[@cjhification]

2, 8 inch holes are a lot smaller than 1 16 inch hole, which is massively smaller than 24 inch hole, so based on your end experiment, you initial statement about possibly needing a 24 inch hole for passive seems like it was an overestimate. Very interesting content as ever. Thanks.

[@zimmermanlandscape9287]

Most people don’t realize a 3x4 gutter is .75 of a 4” square whereas a 4” tile is .785 of a 4” square. They get bogged down with the Greek letters and exponents before they even realize what a ratio is.

[@zimmermanlandscape9287]

It like groarge Carlin always says the education system ain’t going to get better because the owners don’t want that

[@___Q-bot]

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

[@AsHellBored]

seems like a job for a B-vent. like seriously, someone make a B-vent with a little foil or tin crossing the inside to increase surface area. We could call it C-vent, for cooking.

[@dreednlb]

He's got that fancy zehnder system. I wonder why it didn't tie into this.

[@jeffnhelen]

@@dreednlb I though the same thing. Only conclusion I can come to is not wanting makeup air being distributed across the whole house or the ability to have it ramp up to the proper cfm to match the exhaust. Thinking of it that way it does make more sense to have a dedicated makeup air system even if it will bring in some hot & humid or cold & dry air while running.

[@DHClapp]

@@dreednlb The way I understand it, you can't use existing ERV systems for kitchen hood air, because the smoke and grease will clog the exchange membrane. Seems like a hole in the marketplace that someone should fill. Even if it's less efficient than current ERV systems, it would be worlds better than a big hole in the wall with no heat exchange.

[@LIBERTY0RDEATH]

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

[@publicmail2]

Is it air while the wife puts on her makeup?

[@sa3270]

It's so she can do her makeup while cooking.

[@jackl9922]

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.

[@RandomUserName92840]

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

[@sa3270]

No kidding. As far as I'm concerned, it's just something else that's going to break.

[@facklere]

I think the reasoning is that if you have a high enough vacuum inside the house (not enough makeup air coming in) the vent fan won't really be moving the volume of air it's meant to be moving even though it's running. If you had for instance a gas stove, it could be producing carbon monoxide gas as it burns and you could be poisoned from a buildup.

[@mitchdenner9743]

If you listen to the video its code for a reason, saftey. If an exaust hood is pulling negative pressure in a tight house with no way of air infiltration then its going to pull it from other penetrations in the home such as any combustion appliances such as furnace, water heater, dryer, woodburner. These appliances rely on air in the home for combustion and whats called "stack effect" in the chimney to properly exhaust combustion gases. Stack effect is basically hot air rising in your chimney which creates a small negative pressure at the appliances to help exhaust combustion gases. Negative pressure from an exaust hood will fight with the stack effect and could cause your home to fill with carbon monoxide and for you to take an eternal nap. External combustion air should be addressed also for appliances that rely on air in the home for complete combustion to occur. Incomplete combustion causes high CO readings, sooting of combustion chambers and poor efficiency.

[@sa3270]

@@mitchdenner9743 Except, he doesn't have any gas appliances in his new home, from what I can tell.

[@mitchdenner9743]

@@sa3270 its still code in his area and you don't know what the next owner will install or replace. The tightness and insulation most likely won't change but the appliances most likely will.

[@danielweston9188]

Added a BIG whole house fan for evening cooling and had it for about a month. Shut the door one night before turning off the fan (upstairs) immediately smelled the septic tank. Fix was in the next week.......

[@dragons_red]

In commercial construction they know about Makeup Air, in large buildings or commercial kitchens with very high flow exhaust, it's a must or your air balance will be out of whack (negative building) and it will get pulled in through wherever it can, which is usually aome place not desirable. In residential construction, they don't worry about this (so many in that business are ignorant of such things), because your standard bath and kitchen hoods (if you even have one) draw so low flow it doesn't matter, the air needed will pull from gaps and other openings, or just sit there and spin with no actual flow. The standard builder fan is generally a waste of electricity because they don't have that much pull and lack a feed of replacement air.

[@d1daveoh]

Thanks for the video Matt. Yes I learned something and that is I don't think I need to go over 400 CFM

[@peteburnz937]

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

[@dave_dennis]

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.

[@darienredsox1878]

Got induction about a year ago and now I can never go back to electric. It is amazing.

[@kirill_gusev]

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)..

[@K.B.]

Hey Matt! Remember A = π r2 so a 16 " hole would not be twice as big as and 8 " hole. It would be 4 times as big. To get twice as big multiply by √2 (approximately 1.4142) so about 11.3". Thanks for the info however.

[@fox156]

@Matt Risinger So I just replaced my MicroWave Oven (MWO). New GE one runs the exhaust fan continuously every time the MWO is in operation! It runs on low speed at approx 300cfm. Soooo, that is really bad for my heating/cooling and its loud. Not sure how to deal with it and wondering what other MWOs have this "feature :)". GE just a little backwards here, something about protecting their equipment from overheating but most MWOs run an internal fan to cool their components. I think they are telling consumers that theirs is also an internal fan but I disconnected the exhaust duct and verified that its exhausting to the outside during operation. Doubt many/any consumers/installers/builders know this. What fun!

[@norcalstimpy]

A 12 inch hole would be twice the size of an 8 inch hole (area of a circle). A 14 inch hole has over three times the area of an 8 inch hole. A 16 inch or 24 inch hole would not needed be needed to double or triple the intake opening. Great video!

[@Troy-Moses]

Excellent point... I did the same calculation on a house I am designing and think that passive make-up air is a better tradeoff if there is a good location for the intake vent; and I settled on an 8" x 20" hole -- 3.2 times larger than the exhaust duct.

[@NathanHarrison7]

This guy has brought building to a whole new level.

[@rasichap]

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

[@cadrmn88]

Induction is awesome and Miele is wonderful. We’ve been at it 10 years!

[@wizardofhyd]

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

[@scottclement6384]

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.