VRP Compliance Calculator (Case 2, Option 2) for Natural Vent?

Lauren, If you don't hear from anyone else, I'll at least give you my understanding of the Natural Ventilation requirements (all, please correct anything about which I may be mistaken): IEQp1 requires that you meet the ASHRAE 62.1-2007 section 5.1; Natural Ventilation (In addition to the other requirements for outdoor air quality, intake location, etc.) This section states that the "openable" area of the window/door must be 4% of the floor area being served, and the space must be within 25' of the exterior wall opening. IEQc2 states that naturally ventilated spaces must comply with the flow chart found in CIBSE AM 10 , fig. 2.8, AND show figures and calc's to show you are meeting the recommendations of CIBSE AM 10 (Or you can provide a CFD air flow model). CIBSE is a European organization, and I had to call a rep in London to order the AM 10 & AM 13 books. To the best of my understanding, there is not a clear cut definition for what "meets CIBSE" (No prescriptive checklist of items, anyway). The airflow numbers I used were from the CIBSE AM 10 section 4.5 - Reservoir Effect. I used the CO2 concentrations for acceptable indoor setpoint, and outdoor levels found in the LEED Reference Guide, to determine the flow rate required to limit the concentration of pollutants. I then made sure these numbers were similar to the required flow rate for mechanical ventilation in 62.1. I then determined the required "openable" window area using the airflow rate above in the Area equations of CIBSE AM10 section 4.3 - Design Procedures Using Envelope Models. Unfortunately, in my case the requirements appeared to be less than that required by ASHRAE for the prerequisite... Hence my hesitation to use the calc's for submission, and my question below. But I hope this helps YOU out a little, or that you can find a flaw in my process that will allow me to face palm, and get it straight for the future. I believe in your scenario you would need to use the Natural Ventilation case, and would not have a use for the Ez. You may be able to use an explanation that the bathroom/kitchen exhaust are creating an "engineered natural ventilation system" that is providing the equivalent to mechanical ventilation. In this case, I would guess that you could use an Ez of 1.0 (or 0.8 to be safe), assuming the exhaust is along the interior of the space, and the open window is on the opposite exterior wall. Good luck!