Make Up Air - Kitchen Hood in a tight new Build

"Gas stoves are polluting our homes. Over the past decade, a growing body of scientific evidence has shown that gas stoves throw off pollutants like nitrogen dioxide and carbon monoxide. When you are cooking, those invisible pollutants can easily reach levels that would be illegal outdoors, but the Clean Air Act does not reach inside the home.”

Also read this on WHY YOU NEED TO USE YOUR RANGE EXHAUST HOOD from Stanford Medicine.

It’s really important to use your kitchen exhaust, but if you BUILD a tight home and don’t supply Make-Up Air that exhaust may not actually suck much air out of your house. In today’s Build Show Matt will will show you a simple but very effective way to ensure your Kitchen Exhaust Hood will function as rated.

Links to some of the items in video:

(you’ll need to size this based on your exhaust CFM.


Huge thanks to our Show sponsors Polywall, Huber, Dorken Delta, Prosoco, Rockwool & Viewrail for helping to make these videos possible! These are all trusted companies that Matt has worked with for years and trusts their products in the homes he builds. We would highly encourage you to check out their websites for more info.

[claystorm]

Also, something to think about is tempering your makeup air. Work for a commercial HVAC company, so this was nothing new for me. But, depending on where you live (really hot / really cold), you might want to temper your makeup air. Otherwise, on a hot Austin day, your dumping a lot of heat into an already hot thing, so if your “slaving away” at the hot stove, drawing in 90 / 100°+ air will make that feel even more miserable. Or likewise, if your somewhere really cold, you could be dumping literal freezing temperatures into your kitchen, which could affect the temperature of what’s on your stove. And while yes, the hood should in theory capture most of this, if your HVAC system is running while the exhaust fan is running, my guess is you’ll get less capture of that makeup air from the hood then you’d like. Yes, it can be expensive to do, but in the same regard, it might be worth it.

[ezophoto]

Based on the codes, make up air is supposed to be minimum 8 feet away from the hood.

[IAmKyleBrown]

I love this. I'm moving my make-up air from the basement to come up right under my range. The air will come up over the front of the range and pull grease and steam. I believe all high output stoves should have this built into the front of them.

[tomtillman]

Great idea, and actually required by IRC code if the hood is, I think, 400 cu ft or more. Otherwise the house will be under negative pressure when the hood runs, If you have built tight.
I did this on the house I just built for myself. I have a cooktop on the island, and the vent is on the surface of the island, right next to the cooktop. It goes to an intake at the rim joist, that looks like a foundation vent, and the filter is there. I had put a damper on it that was supposed to open upon a draft, but the spring is a bit too strong. So it just has a filter. Next time I will probably motorize it, so it just opens when the hood fan runs.

[erickessler]

Hi Matt,
Gr8 topic. That was a major concern for me when I was building my ICF house 4 years ago which is very tight and with a balanced flow from an ERV. You might recall advising me on that. Well, We just a normal range hood with an inductive cook top, nothing so elaborate. But we also have a whole house Vacuum & Dryer which blow out air.
My solution was to use my UltraAire XT105 (another item you recommended) & its very handy auxiliary fresh air intake.
The cool part is i have 3 current sensing switches that sense if the hood, vacuum or dryer are on... the then activate & open the 100cfm XT105 auxiliary air intake.
I love the UltraAire XT105 for some important reasons... the make up air is a big one.
Thx for your years of advice!

[hotstreak]

It would make more sense to locate it at the base of your range, creating a curtain of air that moves upward.

[joshuas]

I would like to see more about this topic specifically for retrofit applications. My wife cooks in the house just about every day and the smells linger. I also just put in some new panasonic bathroom fans and when they turn on you can tell they are causing the house to pull in air from various locations. I would like to be able to sync up a make up air system when either a kitchen or bathroom an comes on.

[seanpalmer]

I'm not really sold on this setup. In a tightly-sealed modern house, you are already going to have an ERV/HRV. I would say just put a fresh air supply _somewhere_ in the kitchen (not even near the stove necessarily) and let _that_ system temper the incoming air. Granted, it would lower the ERV/HRV efficiency since the air going out through the hood wouldn't be going back through the heat exchanger, but you wouldn't be be dumping unconditioned air right on the person in front of the stove. There also wouldn't be a potential "short-circuit" problem either.

[narutofanar]

As a operating HVAC tech, I'd definitely frown upon putting that damper in a tight space. It's not a question of if it will fail but when. That and I've already seen a few other members of the trade noting the actual ductwork. I love the channel, Matt, but I'd take a closer look at what the difference is between a good setup installed sub-par versus a good setup installed to spec.

[kurtzimmerman]

Glad to see you trying to actually to bring make up air into the equation. When I did new hvac construction, the builders didnt care about the heating or cooling the house correctly, much less make up air for an exhaust system.

[kylemacht]

Thank you so much for posting this, I didn't consider this location, I have specified under the range, under the refrigerator, other places, but not right next to it. I love it!!

[luke]

What you want is a chimney effect with range hood exhaust. Bringing in air right there pointed at the source of the smoke and smells is going to blow that air and smoke all throughout the room, and displace some of the air you are trying to exhaust when some of it makes a hard U-turn up the vent.
Replacement air just needs to makeup for the negative pressure the exhaust is creating in the room, and should be anywhere else than near the exhaust source. It's like pointing a HVAC supply register right at a return.

[jeffmoco]

Wouldn't a setup like this create a short-circuit where the vent will actually just be pulling only the outside air our of the house without much of the particles from the range being captured?

[philiparmand]

The path of return air vs suction induced by the vent is just short circuiting the cooktop. Ideally the path of fresh, return air would be under the stove or in the kick of the cabinet below the cooktop. This would create a path that pulls air past the cooking surface. I have a window near my vent hood. Opening it causes the air to go from the window to the hood, bypassing the cooktop. It tends to not help remove smoke or steam very well. This will be a similar weakness in design. Yet I understand the constraints of design and structure and as shown this is much better than no fresh air return.

[MrMikeyPayne]

I was planning to copy this idea, but there are some concerns brought up on a Green Building Advisor Q&A: "Kitchen Exhaust and Make-up Air in One Range Hood" and while it looks good, is not such a good idea. Thanks so much for all your great videos Matt. I have learned so much over the last several years and it was you who set me on this journey, and I am a bit of an evangelist telling people to look into it.

[brettster]

Great video Matt, I put the make up air in my kitchen in the floor near the range, it works so well and is so much better than heating or cooling all the air going up and out the hood.

[TheProCut]

have you or can you do a video on all the ventilation systems on these tight builds? IE: dryer vent, bathroom humidity fan, etc

[bestbuilderst]

It appears as though someone didn't follow the manufactures specs when they installed the hood fan. The hood will not function as designed. Usually, they require a 27" to 30" max/min distance above the cooktop (cooktops are usually at 34.5" to 36" off the floor) and unless Matt shrunk a whole bunch and is now under 5'6", the hood will not function as designed. All the air that was supposed to go up the duct will be just the makeup air and the steam and grease will find somewhere else to go.
By adding the makeup ducting in the front; you have to make the hood surround huge and thus have to raise it so you can cook without smacking your head on it. The fan hood is for residential and not made for this application (unless I am mistaken- doubtful, provide model number).

[woohunter]

My range hood is 3 speed, 250cfm, 500cfm, 1, 000cfm, I use the first setting if using 1 or 2 burners, 2nd setting is 3 or 4 burners and oven, 3rd setting is if I burnt something or cooking something like salmon in a skillet, lol. If I have to use 3rd setting I will open a window, there is no returns in the kitchen or adjacent hallway.

[trustbuster]

I find these videos interesting, but I must say the real take-home lesson is that I am very lucky to live somewhere where you can actually open a window occasionally. Apparently, Houston is not such a place. You have to think all these people living in sealed up houses with their carpets and paint and such slowly off-gassing are going to end up with long-term lung problems or worse. I have a whole house fan, and while there are plenty of days I button up tight because it is too hot or too cold, I rarely go more than a week or two without opening up the windows, flipping on that fan and replacing all the air in the house with fresh air. Even hot summers occasionally have a cool evening or the occasional warm afternoon in winter, allowing this to happen at minimal or no cost. The idea that I should be afraid of pulling a bit of fresh air from outside when running the range hood for 20 minutes or so is just insane to me.