I've done a recirculating hood with an ERV in Berkeley, the city did not notice.
Thanks for the reply George, having followed around inspectors as part of the pickup crew for years, if you've made a good job of it in all phases, you pass inspection.
Recirculating range hoods are in fact in violation of CA state code, but I've seen a lot of them. In fact, even vented microwave range hoods are in violation of state code because none of them meet ASHRAE 62.2's HVI-rated sound requirements. IN FACT, unless their flow is measured as installed, nearly every range hood installed in CA is in violation of state code because only a tiny, tiny proportion (like 3 in 3000) of the range hoods in the HVI directory are rated for sound and flow at the duct static pressure required by ASHRAE 62.2. 62.2 requires them to be rated at 0.25 Pa and almost ALL of them are rated only at 0.10 Pa (so the flow looks better). I realize that this sounds unbelievable, but feel free to investigate yourself (http://www.hvi.org/proddirectory/), and let me know if you come to a different conclusion. As I mentioned before, we're not paying enough attention to kitchen ventilation.
This is pretty unsettling! To clarify, the presence of a recirculating hood is not a code violation, the absence of an exhausting hood is the code violation, in residential buildings with three or fewer stories. In Passive House, both a recirculating hood (to filter grease and smoke) AND an exhaust to the exterior (HRV or ERV) is typically used. ASHRAE 62.2 calls for either 100 CFM intermittent or 5 ACH continuous in the kitchen. Passive House typically employs a continuous ventilation rate with a boost during cooking, but neither the boost nor the continuous rate usually meet the separate standards of ASHRAE 62.2 (this depends on the definition of "kitchen volume.") It is unclear to me whether the Passive House method results in more ventilation than the 100 CFM intermittent option does, as the schedule of operation is a key factor. 5 ACH continuous (i.e. 24/7) ventilation of a kitchen is a high rate indeed, given how infrequently a typical residential kitchen is used.
Thanks for the clarification, Graham, about the absence of a vented hood being the problem, rather than the presence of an unvented hood. As for whether or not the ERV boost approach provides the same ventilation rate as 100 cfm intermittent...I guess I would posit that it's not quite the right question. In my mind, the right question is more like, "what percentage of the kitchen pollutants being emitted are being exhausted (or, potentially, filtered...though that's a discussion for another time)?" And I think the answer to that question is that in general, that capture efficiency percentage is significantly higher for a vented range hood (ASSUMING IT'S USED) than it is for a general kitchen ERV exhaust inlet. And as for the 5 ACH continuous kitchen exhaust "kitchen volume" conundrum...my understanding is that determination will likely soon be rendered unnecessary.
Good point, but the Passive House system is also running continuously, which would tend toward higher capture efficiency as contrasted to a situation with low vented range hood usage. While the intermittent rate may be higher, its duty cycle may be quite short, and rate x time = effective ventilation. I would posit that a Passive House has higher air exchange rates than a typical house, including higher overall kitchen ventilation rates.
Another critical part of this discussion is the role of unvented gas appliances inside a home. There's a fair bit of nasty stuff released into the building from a gas burner. I learned from BPI training that the carbon monoxide release from the startup of a gas oven is ghastly...
Thanks for your response Graham. May I raise a followup question: The Zehnder systems that I am considering are rated to move 118 to 218 cfms. Why would this not meet the ASHRAE 62.2 100 CFM intermittent requirement?
If you applied 100 CFM to the kitchen on demand, it would meet the 62.2 requirement, but you would be over-ventilating, since there is a continuous exhaust function occurring 24/7 in addition. Passive House aims for ~0.3 ACH continuous ventilation for the entire house, as an optimum between air quality, energy efficiency and, in cold climates, indoor relative humidity. A typical residential Passive House ventilation system draws air from the kitchen and bathroom(s) and supplies air in bedrooms, living rooms, etc. In the name of simplicity, the boost controls (in kitchen and bathroom(s)) merely boost the entire system up, rather than zoning the boost, but I suppose this could be enabled, if it seemed worthy of the investment and complication.
I have some updates on the AAVs and kitchen vents from a home inspector in Berkeley. She told me that in a remodel project like mine no kitchen exhausts are required. And they do allow AAVs in some cases and they are happy to consider my application for one.
While code may not require adding ventilation to an existing kitchen, I would never air seal & insulate a house without adding it (or at least recommending it). If you remodel a kitchen it should be required.
As for the AAV's they would be happy to consider your $$$$$$$$$ application, and may or may not approve.
No one here is advocating putting in a kitchen without any kind of ventilation. Indeed what I have assumed all along is a HRV with a recirculating exhaust system over an induction cooktop. The gas cooktop/ wood fired pizza oven goes to the outside kitchen, where we plan to do most of our cooking, given the beautiful/mild bay area weather throughout the year.
I asked a simple question whether AAVs and recirculation exhausts system in Berkeley would be permitted and hoped that contractors/builders familiar with code and enforcement here would be able to provide an answer. The best response came from a home inspector that I spoke directly to in the permits office in Berkeley. She said AAVs are ok in limited cases and no exhaust systems are necessary.