Makeup Air in Near Passive House
Hi,
I am naveen, We are installing a Thermador Freedom Induction Cooktop, with 350 CFM Ventahood Exhaust Fan(32 inches above cooktop) in the Kitchen. An ERV outlet is 8ft away from Cooktop. House is expected to be less than 1ACH@50 Pascal(target is about .80ACH@50 Pascal). We cook on daily basis with all sort of spices and ocassionaly moderately greasy food( we do not grill inside).
Since there is no gas cooktop,
1. do i really need 350 CFM?
2. do i really need to setup make up air?
3. Moment i puncture exterior walls with vents i am going to loose Air Tightness and not sure how much of energy savings with it.
Ventahood non-venting exhaust systems are super expensive(about5k+) and i am not able to find a demo piece in and around Ohio. i have to go to NewYork or Dallas, making it hard to make a decision. I am long time user of ventahood and i feel rest of the market is nothing but glorified noise makers.
So i am wondering if it really make sense to puncture the envelope by venting outside and loose energy savings.
No i have not seen a single article that justifies make up air in a tight house(ofcourse for valid reason), but then i will have to eat only foods off the cold storage section and breads.
Appreciate your insights
Thanks
Naveen
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Replies
What do you have that would be effected by a negative interior pressure?
Sounds like you are planning to have a balanced ventilation system, and no combustion appliances (no wood stove, right?), so as Jon is alluding to, you may not need make up air for your range hood. And like you said, you also may not want to put another big hole in your envelope. I worked on an article with the team at Zero Energy Design a few years ago. When they are in your situation, they use a recirculating range hood and I believe they like the products from Best: http://www.bestrangehoods.com
As long as you have a good strategy for whole house ventilation, you don't need makeup air for your kitchen fan. Code requires MUA for exhaust fans greater than 400 cfm. All our houses have around 1ACH50 with outdoor exhausting fans, and as long the wall penetration is sealed correctly and the fan has a good damper, you should be fine. Kitchen fans do not run continuously.
I respectfully disagree with Brian on one point, I would never specify a recirculating exhaust fan, like someone else said long ago, "recirculating fans are like recirculating toilets".
To be fair, it *IS* possible to make a recirculating toilet, they do it in space for example. Not practical and not cost effective, but possible.
Ha! There is no such a thing as a recirculating toilet in space. The waste matter goes into trash capsules that are released into space, then it renters the earth's atmosphere and burns up. Depending what they eat, it could be "great balls of fire". (Sorry, I couldn't resist. Shame on me!)
IMO, if you cook spicy and/or greasy food (you know, the stuff that tastes good), you want to capture it and send it outdoors quickly, before it spreads to the rest of the house. Having an induction range reduces certain types of contaminants, but there a lot of other things you still want to exhaust.
Have you read BSI-070: First Deal with the Manure, at the Building Science website? He details an approach for providing makeup air for exhaust fans, both ridiculous sized (1000 cfm), and more reasonable 200-400 cfm...of course you can get away with lower flow rates if your hood does a good job of capturing the effluent in the first place. I don't think the approach is costly for the design shown in Figure 4 of that BSI article.
PS - @ Armando - Resistance is futile :)
Good call... for the folks who don't know what "BSI-070: First Deal with the Manure" is... here is the PDF. Kitchen ventilation starts on page 4.
With Ventahood 200-300 CFM i would be able to capture effluent and there by optimally utilize Figure4 setup suggested in the article.
Just in case i am going with Whirlpool Heatpump Dryer, with Sanden CO2 WH...i see no need exhaust other than whats exhausted through ERV.
Thanks to all.
Ducted range hoodsneed ducting to work, and they have both top-venting and rear-venting configurations. Top-venting systems run a duct from the top of the hood to the ceiling; rear-venting systems, on the other hand, run from the port in the back and lead the duct through the wall.
I’m curious – if going with a less powerful kitchen exhaust setup <400cfm, is it still advantageous to have an overhead hood? Or would rear/side downdraft exhausting be sufficient?
I’m kind of assuming that downdraft ventilation is less effective at “catching” the non-desirable byproducts when cooking on a range, and so with a less powerful exhaust setup one should opt for an overhead hood. But would love to hear if any experience or science behind this.
downdraft is WAY less effective at catching the cooking fumes. A big, deep overhead hood is always best, even if paired with a small(ish) vent fan.