Your location would essentially short circuit the air flow. The hood would be pointless.

Yes, you're overthinking about rats.

Ceiling is another location, middle of the room. Also under the floor cabinets with screened openings in the toe kicks.

Haha yes good point on the rat issue. I've been researching the last few days to see if anyone at all has done any CDF analysis on a range/hood/make up air setup, and while I surprisingly did find something somewhat related, I'm still debating what it means for my application.

Here's an image excerpted from the research paper showing a thermal gradient of a range being exhausted, with a makeup air vent blowing into the room directly in front of the hood at 150 fpm (not passive). You can see how the makeup air brings hotter air from the outside, circulates this air immediately in front of the range, and is eventually exhausted. This would be an ideal setup since the makeup air is serving its purpose and not heating up the rest of the house. Win win.

Unfortunately I'm not so sure what the outcome would be in a passive system I would be installing. I have access to CFD software at my work, but I'm not sure I have the time...I may have to revisit the floor idea and think more about the rats...I like that floor cabinet idea as well.

Full paper for those interested:

https://www.captiveaire.com/CatalogContent/Hoods/ND_PSP/doc/PSP%20CFD%20Study.pdf

That is a commercial range hood that comes out a LOT farther from the wall. It doesn’t really apply at all.

Dont know if you’ll get the square footage needed for a passive system in the toe kick...

Kaseki isn't on the appliance forum. You should ask there

Hey there Milly, interestingly enough, it does appear as if the direction and flow of the active makeup air system is actually pushing all heat to the back of the hood. To my eyes in this example at least, the extra depth of the hood doesn't do much (or maybe it actually helps direct that flow back??) Only a CFD model with a more typical residential setup could answer that though. Either way, the setup clearly doesn't represent mine, but I do think there are some parallels to be drawn.

I think I will end up placing my MUA below the range given the results of the linked model. The curtain of air being pushed down and then sucked back up seems like it could be nicely approximated by a passive system directly below the range. I'm actually surprised this setup isn't recommended more often. I've seen one YouTube video of a contractor showing this install method, but no literature.

There is enough surface area under the bottom of a 48" range to accommodate the flow of two 10" vents so I may just do that. Two dampers from Broan are not cheap though =(. Funny how the hidden costs of a remodel add up.

You had better go back to step 1 and check your range installation instructions. They generally say to seal all holes in the floor and back wall because they are not designed to have air brought in underneath them.

Hi Fred,

Great point, thanks. I had brought up that question with Bluestar recently, and their response to me was the hole sealing was to prevent heat from entering areas of the home that may not tolerate high temperatures. I had originally asked because I also have a hole behind the range I built into the wall with a lid which would allow me to service/clean the entire bottom of the range from the rear.

When we were having a Wolf installed during a kitchen remodel the gas (HVAC) guy said that instead of running a new larger line ($$$) that he could move the existing line over to the HP side of the regulator and put a regulator on the range. Only problem was that the regulator stuck out the back and prevented the range from being pushed all the way back.

No problem thought the HVAC guy, nothing a hammer and a punch in the sheetrock can't handle.

"Uh, dude, you just punched a big hole in to a return plenum that you think is going to have a natural gas regulator stuck in it and in any case will suck whatever is in that area behind the range and around that regulator in to our HVAC system."

Duh.

"I had brought up that question with Bluestar recently, and their response to me was the hole sealing was to prevent heat from entering areas of the home that may not tolerate high temperatures." - That is NOT the reason, which just goes to show you that they will tell you anything you want to hear. ALL clearances are to COMBUSTIBLE materials to begin with.

There is not a single employee at Bluestar that has the authority to contradict or override the "Listing and Labeling" of the third party , independent, testing laboratories. (NRTL) - THAT IS the reason that the testing and approval is done by an independent laboratory.

Hi Fred thanks, what is your thinking then as to the reason to seal up holes in the rear and bottom? I am genuinely curious.

In order to begin to understand it, you would need to buy ANSI Z21.1 for about $650. There is some very technical engineering, even though it doesn't look like it, in the ventilation between walls of the oven and cooktop sides that ensures that the cabinets up against the range will not get hotter than 194°F. If you block the airflow by lowering the range (some people try modifying the feet for thin countertops that make them less than 36" tall), or putting ducts in for MUA, the outside wall of the range will get hotter. If you force that much extra air through the range, (push or pull) you change the way the gas burns, and create CO problems. Even if you can adjust the air shutters to compensate, you would then have to turn on the entire system just to make a pot of tea, in order to get enough air to get a clean burn. With holes in the floor or back wall, the natural draft intended/engineered to cool the outer walls of the range can be disrupted or diverted, leaving the heat to build up around the range - nothing to do with heat in other areas of the home. What can't tolerate more heat than the wood cabinets around the range? Another separate reason for no holes is the possibility of a gas leak. How much gas do you think that duct will hold, just waiting for someone to create a spark?

The testing standards do not say no holes "unless someone thinks of some unusual excuse".

Thanks Fred very informative. I find it interesting how the instructions state to seal up holes in the rear wall and floor, but nothing about the sides. I think there is wiggle room in the design but without talking to the designers directly couldn't confirm. I may vent from the floor on the sides of the range up through the cabinets to be safe though. Thank you very much!

"I find it interesting how the instructions state to seal up holes in the rear wall and floor, but nothing about the sides." That is because the traditional design of a freestanding range has been developed such that the sides are designed to be either exposed or adjacent to a base cabinet.

"I think there is wiggle room" Not enough for MUA. I figured roughly a velocity of 1800 f/m around the base of the range without taking off the front lower panel. That is 3X what a normal HVAC duct would be. That is for a 1200 cfm hood, and if that location of mua was actually of significant proportion.

.

I found this very interesting (and very odd): //Interestingly, exhaust from toilet rooms, bathrooms, and kitchens is not considered hazardous or noxious, and the IRC explicitly allows makeup-air intakes to be located near these vents (in other words, your kitchen makeup-air intake can be right next to your kitchen exhaust-vent termination).//

The Basics of Makeup Air - Fine Homebuilding

www.finehomebuilding.com/project-guides/kitchens/the-basics-of-makeup-air