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Can you satisfy ASHRAE 62.2 with a recirculating kitchen range fan?

David Milliken | Posted in Building Code Questions on

As a Green Rater for the LEED Homes program, I am involved in a fair number of new construction projects that are attempting Passivhaus level building tightness (< 0.6 ACH50). Of course, ventilation systems are a critical piece of all of these homes. All are using HRV/ERV systems to meet the Whole Building Ventilation requirements in 62.2 – Section 4. All are meeting bathroom exhaust requirements of Section 5, with either continuous or intermittent ventilation. However, we have several projects that want to avoid exhausting the kitchen to the exterior – primarily in an effort to meet the Passivhaus tightness standard. My question is about the “Note” in Table 5.1. “Vented range hood required if exhaust fan flow rate is less than 5 ACH” Does this note imply that a recirculating range hood that moves 5 ACH (kitchen) s acceptable? My interpretation of the Note in Table 5.1 is that you need a Vented Range Hood if the exhaust airflow rate is less than 5 ACH. I think this is addressing non-hood style exhaust, such as downdraft. I interpret exhaust as airflow to the exterior of the building, and “Ventilation” is defined in the standard as “the process of supplying outdoor air to or removing indoor air from a dwelling…” My interpretation of the standard is that recirculating kitchen exhaust does not meet the requirements of Local Exhaust, 5.2. However, it could be used in conjunction with adequate continuous ventilation (balanced or exhaust) as part of a strategy to meet 5.3. Can anyone help me clarify the intent of the Note in Table 5.1 – thanks!

Replies

  1. GBA Editor
    Martin Holladay | | #1

    David,
    I forwarded your question to Max Sherman, the former chair of the ASHRAE 62.2 committee.

    Max answered, "Section 5 is about local exhaust requirements. Recirculation is not exhaust."

  2. Armando Cobo | | #2

    we have several projects that want to avoid exhausting the kitchen to the exterior - primarily in an effort to meet the Passivhaus tightness standard.

    Would somebody please explain to me, why would a stringent building standard as Passivhaus allows a kitchen fan not to be vented to the outside and create bad IAQ? Kitchen vents are to be vented to the outside for humidity, carbon oxide and oil & burnt carcinogenic mitigation and also codes are mandating it. It seems to me that Passivhaus standard rather “kill” the habitants than loose some precious ACH; and it’s all going backwards. Am I looking it wrong?

  3. GBA Editor
    Martin Holladay | | #3

    Armando,
    Range hood exhaust fans are routinely oversized. When they are operating, they are exhausting far too many cfm -- certainly more cfm than the ASHRAE 62.2 ventilation rate. They are also generally exhausted directly outdoors with no heat recovery, since HRV and ERV manufacturers specifically advise against hooking up a range hood to an HRV.

    The Passivhaus builders are rethinking the received wisdom on range hood fans, and experimenting with creative solutions to a real problem. All power to them. Certainly the conventional rules of thumb for range hood sizing aren't working. In many homes these fans are causing serious depressurization problems.

  4. Armando Cobo | | #4

    Martin,
    Whether I agree or not with perception, reality or 62.2, the new codes REQUIRES appliance venting to the outside and (as I asked in a previous GBA Q&A) any appliance required of venting +400cfm SHALL have make-up air equal to the exhaust fan AND wired simultaneously. So, how the Passivhaus standard “gets around it”?

  5. Riversong | | #5

    Range hood exhaust fans are routinely oversized

    And why is that? As evidenced by the discussions on this forum, it is either because designers put "chic" above efficiency or simply don't know how to say "NO" to their profligate clients.

    There are 30 Energy Star certified range hoods rated at less than 200 cfm. There are no shortage of choices, only a shortage of common sense and environmental responsibility.

    http://downloads.energystar.gov/bi/qplist/vent_fan_prod_list.pdf

  6. Allan Edwards | | #6

    We've been discussing this at JLC. We use these 6 burner (with separate grill and/or griddle) gas cook tops, trendily called "Professional" ranges, that are high BTU. I can't find any definitive science behind how to size a kitchen vent for these, other than follow manufacturers recommendations, which I suspect oversize the vents. It isn’t uncommon to use 1,200 CFM vents, I’ve heard some now go to 2,000 CFM’s. Any suggestions?

  7. Riversong | | #7

    Suggestions?

    Sure, use reasonable and responsible 30" 4-burner ranges. No one other than a professional chef needs anything larger.

  8. Allan Edwards | | #8

    Robert

    My clients choose to use these large cooktops, I've got to provide proper ventilation.

  9. Riversong | | #9

    Allan,

    You can't provide "proper" ventilation for such monstrosities and build an ecologically responsible house.

    I know that you are simply servicing your client's needs for profit. But there is a term for that relationship. That's why I left JLCOnline. Not the company I choose to keep.

  10. Armando Cobo | | #10

    Allan, be careful mentioning “professional” ranges here... “the green police” will scold you for not building what “they” consider to be “the only way to build a green house, period.” (i.e. small boxes, with funny walls and compost toilets in the middle of Hicksville, where you can explain rules of thumb’s code interpretations to inspectors and get away with it place).
    FYI: The 2009 codes IMC 505.2 and IRC M1503.4 Makeup air required: Exhaust hood systems capable of exhausting in excess of 400 cfm shall be provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system.
    I’ve researched this issue a lot in the last 3 months; appliance and hood manufacturers and retailers, HVAC contractors, Mechanical Engineers, etc. without any help. But I think I have come up with a reasonably cost system ($2K-3K) vs. a commercial ($7.5K-10K).
    I don’t know if this is the answer, but in NM I end up specifying the installation of an 600cfm (OKd by code official) independent tempered make-up air in the kitchen that would have supply vents above the stove, in the ceiling (±12’), providing the necessary make-up air in a close loop http://www.myworksite.com/shelter/htmlArea/files/documents/52_makeupair.pdf . Doing it this way, it would not “tax” the house air or mechanical systems. We’ll see how it tests when the house is finished. Required: 1200cfm w/ all 8 burners going full blast.
    In Dallas, my client is installing a similar system, we’ll see how it tests as well. FYI, Mark LaLiberte told me he installed a similar sytem in his own house a few years a go and works great.

  11. Allan Edwards | | #11

    Thanks Armando, useful information. I visited your website the other day and see you are an architect in Santa Fe? Your link is to Shelter Supply? I called them yesterday and talked to a guy, I think name is Dietz?

  12. Armando Cobo | | #12

    Brett Moyer gave me this link: http://www.electromn.com/gen/makeup_air.htm, it may work too.

  13. Armando Cobo | | #13

    Yes, I'm a designer in Albuquerque, Dallas & Sowthwest. R U in Houston?

  14. Allan Edwards | | #14

    Armando, I am in Houston. There is a Dallas architect named Elby Martin who does some very high end work here in Houston. Where can I see some of your designs?

  15. Armando Cobo | | #15

    Allan, I sent you an email at your company's email address.

  16. Lucas Durand - 7A | | #16

    Allan, be careful mentioning “professional” ranges here... “the green police” will scold you for not building what “they” consider to be “the only way to build a green house, period.” (i.e. small boxes, with funny walls and compost toilets in the middle of Hicksville, where you can explain rules of thumb’s code interpretations to inspectors and get away with it place).

    Armando,
    There is no "green police".
    Robert is correct in pointing out that a professional range for anybody not living in a working restaurant is unnessecary and wateful.
    If they are what your clients want then by all means make sure it's done properly (to code), but please don't try to justify them as something that can be part of a green house. It just doesn't make sense.

  17. Allan Edwards | | #17

    Lucas

    While I agree large, 8-10,000 (or larger) homes with high ceilings, cut up, lots of perimter wall, things like large ranges, swimming pools, several wood burning fireplaces, etc, may not be a "green home", I think architects and builders should still try to apply as many green features as possible.

  18. Riversong | | #18

    I think architects and builders should still try to apply as many green features as possible.

    Lipstick on a pig...

  19. Armando Cobo | | #19

    Lucas,
    With all due respect to all of you, this website I believe, is for anyone to who needs information on specific questions about green buildings, methods, techniques, etc, etc. I do not believe the GBA’s intent is to grade, judge or try to influence our shade of green on others. Must of us work in various shades of green, from affordable housing projects to megamasions and its not our place to tell our clients how big, small or shade of green of a house they should live.
    I know Robert is extremely talented and knowledgeable builder, and I have learned a lot from him in the past, but too often he takes the right to “inform” us (including me) how green building should be. I guess he misses Michael Chandler and needs someone else to pick on. :-))

  20. Allan Edwards | | #20

    Robert

    Pigs need luv too. If we're going to restrict our efforts to those homes that meet your standards, we'll miss about 98% of the market. That doesn't environmentally smart to me.

  21. Riversong | | #21

    Armando and Allan et al:

    I don't "pick on" anyone. This isn't about either me or you. It's about ideas and methods and materials to address the perfect storm of global crises that threaten both human civilization and the terrestrial biosphere. This is a forum to address "green building", and the most important part of that discussion is what constitutes "green".

    What I will continue to challenge is the appropriation of the term "green" by designers and builders who are merely dressing up the hogs we call houses either for marketing advantage or under the false belief that painting the Titanic green (slightly improving the efficiency by which it approaches the iceberg) is going to avert catastrophe.

    Far better global thinkers than myself are asserting that we have perhaps ten years to shift course if we are to have any chance at all of steering the ship of human civilization away from the precipice. All the indigenous peoples of the world know that this is true and are offering their wisdom and experience to those who have ears to hear.

    The "market" is created by millions of personal decisions. You may not have the right to tell anyone else how to live, but each of us has the inalienable responsibility to make appropriate, life-affirming decisions about what we're willing to be complicit in. Anyone who decides to receive personal gain by participation in destructive activities (such as perpetuating the inordinate excess of American life) is an enemy of the web of life. These are the true terrorists of the world. And there is nothing "green" about terrorism.

  22. Riversong | | #22

    By the way, for those who are sick of hearing from me and would rather read the latest blog from an all-American workin' stiff who really "gets it", Joe Bageant, author of Deer Hunting with Jesus, check out: http://www.joebageant.com/joe/2010/05/blogging-toward.html#more

    This crude and politically-incorrect man understands more than almost anyone where we're heading and why (and that's why he jumped ship and moved to Mexico). In this new missal from down under, he also sheds some light on where we need to go.

  23. John Brooks | | #23

    I agree with Lucas
    Nothing wrong with Robert (and Martin) pointing out that certain practices are foolish.
    Maybe 1200 cfm exhaust fans should be discussed at the Not-So-Green Building Advisor

  24. Allan Edwards | | #24

    I can handle being called a terrorist by Robert, but now you guys are starting to sound a bit elitist.

  25. Armando Cobo | | #25

    Robert, the points you bring are worthy of discussion in a separate blog or question, however the manner, timing and tone of your some of your comments are usually out of question, rude and green “fascist”; as your friend who “gets it” points out (a drunk & rude person whom you admire; surpriced!!!). Unfortunately is becoming quite popular and profitable to be on the extremes and fringes of almost any issue, without regards that most of us live in a real and somewhat compromising world. To get where we all want to be, we need people that are extreme, middle and low green. Not everyone is for green building, but a push and nod can go a long way towards educating all. Fascist, intransigent, antagonistic and rude comments turns people off and the whole point of this website is to educate and share experiences, not to force ideology.
    I hope the GBA corrects this issue, this is getting old!!!.

  26. Allan Edwards | | #26

    Well said Armando. I think people who are very dedicated and committed (sometimes with almost a religious zeal) to green building and general overall energy efficiency, who have immersed themselves in it, have to be careful to not turn off those who (1)are beginners (2)are committed but to a lesser extent (3)don’t perfectly mesh with their lifestyle model.

  27. John Brooks | | #27

    Allan,
    Are you saying that I should be committed? ;-0
    I respect you and Armando.
    I have done my share of Mcmansions and starter castles
    and I will accept the criticism that comes along with it.

    I also respect Martin and Robert and the Building Science knowledge that they share with the rest of us.

  28. Jesse Thompson | | #28

    Back to the original thread:

    "Would somebody please explain to me, why would a stringent building standard as Passivhaus allows a kitchen fan not to be vented to the outside and create bad IAQ? Kitchen vents are to be vented to the outside for humidity, carbon oxide and oil & burnt carcinogenic mitigation and also codes are mandating it. It seems to me that Passivhaus standard rather “kill” the habitants than loose some precious ACH; and it’s all going backwards. Am I looking it wrong?"

    Passivhaus(es?) always have a full house ventilation system, they are extremely strict about air quality and exhausting bad air from the house, but they also always make sure there is a pathway for return air to come into the house. This is the major flaw in current US practice, the vent hoods being installed are very dangerous when combined with combustion appliances without make-up air in modern construction (not just very air-tight houses, but just about any house with tyvek and modern windows...)

    The passivhaus kitchen theory is to use a high quality recirculating vent hood (that can pull high CFM without depressurizing the house) to clean the air around the stove through the filter (trapping particulate, grease and other bad things around the cooktop) and then set the HRV exhaust in the kitchen in a spot where it can continuously draw off air at a rate where it won't pull the aerosolized grease laden air into the ventilation system.

    From what I can tell, ASHREA 62.2 makes it very difficult to implement a system like this in the US with their requirement for a continuous system that can produce 5 ACH in the kitchen.

  29. Garth Sproule | | #29

    I don't think anyone has built or designed one yet, but I really don't see why a properly sized and designed recirculating hood unit cannot work. By using washable grease traps as well as large activated carbon filters, I see no reason to vent outdoors. A properly sized HRV could be inter connected with the hood to run on high when the hood fan runs. This should easily handle the humidity and combustion gases associated with cooking. No energy penalty. Anybody see why this cannot work? Flame away folks...

  30. Jesse Thompson | | #30
  31. Garth Sproule | | #31

    Jesse
    Thanks for the link. From looking at the list, it seems that all are mainly designed to vent outdoors....some are convertible to recirculating but it seems like a feeble add on for most of them. I would like to see a dedicated recirculator with a good sized variable speed quiet fan, dishwasher safe grease traps and fan wheels, and a large AC filter.
    I suppose the reason that all are designed to vent out is to meet codes. Anyone know of any code approved dedicated recirculating hoods??

  32. Armando Cobo | | #32

    Jesse & Garth,
    Thank you for bringing us back to the original thread and your link. The new codes (see #10) DO require MUA and none of the 23 fans you linked have MUA. So we must provide the MUA with an equal amount of exhausted cfm, hence I’m looking for an HRV or ERV with a 1500 cfm that is NOT A COMMERCIAL UNIT (as in $7K-10K and the size of a VW). Since I have not founded, I came up with the solutions I described before. We’re trying this out for now and we’ll test later. I can update this post when that happens.

  33. Armando Cobo | | #33

    I really wanted to say 1200 cfm not 1500 cfm, but anything between 600-1200 would do.

  34. Armando Cobo | | #34

    I'm sorry; now I'm all POd that can't say what I want. What I need is a 600-1200 cfm SUPPLY ONLY MUA unit that not only heats but cools the MUA @ that volume, that does not cost $7-10K and is the size of a VW, like commercial units are.
    If anyone else has done an experiment like I’m doing, please let me know. I know we’re all going to have to deal with this new code issue anytime any of our clients insist on these particular ranges and hoods.

  35. Allan Edwards | | #35

    I’m having a hard time understanding make up air for a kitchen vent. You have say, a 36”-48” cook top, a shroud 30” above the cook top, and a motor sucking the air from the open area above the cook top, which of course is open to the rest of the house. Where is the makeup air intake located in relation to the vent hood or cook top? Anyone have a diagram?

  36. Allan Edwards | | #36

    Im my previous question I'm asking about a vent hood that exhausts to the outside, not recirculating.

  37. Garth Sproule | | #37

    Allan
    The MUA intake would be on the outside of the house...the outlet could be somewhere in the kitchen. But come on guys, don't you find it to be a bit ludicrous to be talking about huge exhaust hoods and heated/cooled MUA units on a green building forum?? We should be pushing for code changes to make properly sized quality recirculating range hoods legal here in America. No reason they can't do the job along with HRV's, with less installed costs and NO energy penalties.

  38. Armando Cobo | | #38

    Allan,
    Think of the way commercial hoods work on a restaurant but in small scale. The intake MUA needs to be at least 10’ away from any exhaust vent. The supply MUA needs to be close enough to the exhaust fan so it creates a close loop and you are not increasing work on the HVAC system of the house but far away (10’-12”) that it would force to exhaust all humidity/gases from the range. The motor can be installed in between the floor trusses of a 2nd story house or roof trusses/attic on a single story. See: http://www.myworksite.com/shelter/htmlArea/files/documents/52_makeupair.pdf.
    One of my clients had an engineer do a provisional drawing. He had a double bell hood that would not work because the supply was next to the exhaust and it would draw directly form the supply to the exhaust without pulling any of the humidity, grease or odors. Also, the intake vent needed to be at least 10’ away from any exhaust vent.

  39. Armando Cobo | | #39

    You are right Garth. I've spocken to ICC and was told the 2012 code changes were closed for now and they are in public comment as we talk. I did write a code change but it's out of my control now. I also try to explain that for the moment it appears there is no solution for residential kitchen's MAU of large size. How knows, we'll se what happens!!!

  40. kevin omeara | | #40

    It is interesting to see the same question I posed surface once again! cooktops present a real challenge when trying to meet the ASHRAE codes while also trying to satisfy PAssivHaus criteria. In europe a common practice is to use recircualting hoods. Besides the ones we are familiar with here on this side of the pond, which incluse washable grease traps mated to activated charchoal filters, they have another option. a company called Berbel makes a recircualting hood that works with certifugal forces to good effect., however they are not cheap!
    People have run the exhuast through an HRV/ERV, using lower CFM hoods, and had them work for prolonged periods of time. It does require that the HRV have metal exchange plate...usually aluminum, so that they can be washed regularly, but alas you'll invalidate your warranty in the process. I would tend to trust the european approach if for no other reason than it has a track record.

  41. Kevin Dickson, MSME | | #41

    For a modest house with a modest electric stove, the guys at 100k are really doing the state of the art:
    http://www.100khouse.com/2010/01/20/passive-house-ventilation-design/

    I'll soon be building something similar, probably using a cheaper ERV: http://www.amazon.com/Panasonic-WhisperComfortTM-Ventilator-Ventilation-Patent-Pending/dp/B000XJNZ1Y

  42. Michael Chandler | | #42

    Late to the party here, but we recently did a hood for a glass worker that incorporated conditioned make-up air in the hood and it was quite simple, (except the elbows). We used a 300 CFM roof top exhaust fan and a slightly smaller in-line blower for the make up air drawing from an externally filtered inlet just under the roof overhang. The intake blower was in 10" galvanized pipe and the roof-top exhaust was in 6" pipe. Just inside the wall the make-up blower passed through a ten-inch wye with a six-inch elbow in it that fed out through a ten inch end cap on the wye with a six inch A-collar in its center to the roof mounted exhaust unit. (that was the first hard part) from there it was concentric six-in-ten to just above the island hood where the ten was cut a few inches short to distribute air around the perimeter of the hood with the six pulling from the interior. We sized the intake smaller because it seemed intuitively that there would be more resistance in the six but after assembling that wye and two concentric elbows I would guess that that was probably a bad assumption and we should have done flow hood testing on it at wall and rooftop and adjusted the flow of the in-line fan accordingly...

    You can see a bit of an image of it here but the theory is the thing, the intake venting has lots of concealed blood staining from the tin-knockers knuckles, those concentric wyes and elbows are a bear. http://limemoonart.com/classes.shtml

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