usu a single 100cfm+ continuously running fan will cover it.

Hi, Peter,

California references ASHRAE standard 62.2-2007 as its ventilation code. The required ventilation is a function of the size of the living area and the number of bedrooms. Here's a link that you may find helpful:

https://homes.lbl.gov/ventilate-right/californias-ventilation-requirements

If your local code is enforcing current international ASHRAE 62.2 then the formula is something like:

.01 X Floor Area + 7.5 X(#of bedrooms +1)

There are no requirements for specific areas that I know of. Only meeting the total ventilation CFM-in requirements, you can exhaust however you want.

Alison Bailes writes that 2021 will allow a 30% decrease in above formula if using balanced system like HRV. Whatever your locality is enforcing it's wise to include a third party energy rater to help with your system design and commission it after installation. Don't count on your savy internet skills nor the HVAC contractor's craftsmanship to get all of this right, though we commend you on your progress so far. Most building a home here, don't even know what you're posting about!

Thank you that is very helpful. I found the following article that covers both ASHRAE, BCS and IRS and yes balanced systems are receiving 25%-30% credit. For my house they all come down to 115-120 cfm which surprisingly is quite close to the 0.3 ACH - 116 cfm. Adding the article here for others reference:

https://www.phius.org/NAPHC2016/Klingenberg-PHIUS+Ventilation-Protocol-and-Best-Practices.pdf

Not so fast, Springtime...

Meeting ASHRAE 62.2's requirements for continuous ventilation doesn't eliminate the need for point source ventilation in Kitchens and baths as well. ASHRAE 62.2 gives the options for Kitchen ventilation @ 100 cfm if operated intermittently or 5 air changes/hours (ACH) if continuously operated. Options for bath ventilation are 50 cfm if operated intermittently or 20 cfm if continuously operated.

The standard does give a "kill two birds with one stone" option if you use a bath vent fan to meet the continuous ventilation requirement, but this would be an approach for affordable (low budget) housing.

Since the building code is regulated by the state, you may find some conflicts between the ASHRAE standard and the IRC. It's a good idea to check with your local building department to ensure compliance with the code in your area.

Hi Charles,

thank you for that comment. The system I am designing (HRV) will operate at ASHRAE levels at 50% of the capacity so with boost I can increase almost twice. it is balanced and kitchen is 24 cfm @ 50%. Additionally I will have 500 cfm range hood with make up air supply.

Yes Charles, that was poorly worded and should have realized OP was looking to eliminate spot ventilation in place of continuous, something me and my energy rater are not fans of. There is also a rule about distance of continuous kitchen exhaust from cooktop.

Here is the table from my blog on 62.2 if it helps:

@ Springtime, I can't read your table except for the "Ventilation In" and "Ventilation Out" headings. At a minimum, I suggest there's a nomenclature problem. Ventilation is the process by which stale air is exhausted and replaced with fresh air. That definition holds true whether we're talking about human lungs or buildings.

For homes, there are a variety of whole-house ventilation strategies including supply ventilation (pressurization); exhaust ventilation (depressurization); balanced ventilation, and energy-recovery ventilation. I think your table would be more accurate and more clear if the headings were "intake air flow rate" and "exhaust air flow rate."

Charles, you have to click on "table" link to see the full size version. Reading the blog may also help someone not fully understanding these issues. The table was created to simplify the math, and make a quick reference of the numbers involved.

Thanks for the feedback, I will certainly try to do better in the future. After just searching ASHRAE 62.2 tables, I still think it's a decent attempt at simplifying some of the important details of the subject, at least in comparison to what's out there. I believe this was written close to 9 years ago and surprised the specifics haven't changed much.