Hi John, I have attempted to answer your questions from the two emails copied below starting with the email from Tuesday. Tuesday Email: Yes. Note that for VAV systems it may be sufficient to set the block airflow in the Create Systems - Advanced window. The VAV box will still modulate assuming the Clg VAV min in the VAV control section of the Create Rooms - Airflows window is set to less than 100%, as it is in the screen shot that you provided. Assuming the pretend building you are referring to is the ASHRAE 90.1 Appendix G Baseline alternative, than you should not manually change these cfms to match the design. Instead, the Baseline airflow is required to be autosized based on a 20 degree delta t between the design cooling supply air temperature (set both the Cooling Supply Max and Min values in the Create Systems - Design Temperatures window) and the design cooling setpoint for the spaces served by the system. Note that the Main Cooling coil capacity units on the Create Systems - Heating and Cooling Coil Overrides window should be set to % of Design Cooling Capacity instead of % of Design Capacity by Adjusting Airflow. Enter the scheduled pump motor values. Wednesday Email: I normally set the Baseline model outdoor airflow manually by setting Apply ASHRAE Std62.1-2004/2007 field to No and entering the average ventilation airflow per square foot into the Cooling and Heating ventilation inputs. I calculate the ventilation airflow per square foot by taking the total design outdoor airflow associated with each Baseline system and dividing by the sum of the floor area of the spaces served by that Baseline system. The only issue you may run into is if you have a system with a minority of rooms with a high percentage of OA to SA ratio and by averaging the OA over every room served by that system you end up with a lower VAV minimum for those outlier rooms, but this is conservative, therefore the reviewer shouldn't have a problem with it. In response to your side note: You should make sure that your Proposed Case model reflects the design and that the Baseline Case model has constant ventilation airflow independent of the hourly supply airflow of the VAV system. Note that to get TRACE to model constant OA in a VAV system, the Fixed return / outside air dampers box located in the Advanced Options sub-window of the Create Systems - Options window must be unchecked. Also, if the design has a fixed % of OA (such as the 30% mentioned in your email), ensure that the minimum 62.1 required ventilation is still supplied during the minimum expected VAV box position during the course of the annual simulation to comply with Section 5.4 of ASHRAE 62.1-2007. You could do that, or see my response to question #1 above. I hope that helps and good luck! Alex Alex N. Chapin Sustainability Program Engineer SRI Green Building Certification, LLC 300 Northpointe Circle ? Suite 304 Seven Fields, PA 16046 ? USA www.SRIRegistrar.com achapin at SRIRegistrar.com T: (724) 934-9000 x619 F: (724) 935-6825 Building Sustainability This message and any included attachments are from SRI Quality System Registrar, and are intended only for the addressee. The information contained herein may include privileged or confidential information. Unauthorized review, forwarding, printing, copying, distributing or using such information is strictly prohibited and may be unlawful. If you have received this message in error, or have reason to believe that you are not authorized to receive it, please promptly delete it and notify the sender by e-mail with a copy to mail at sriregistrar.com. Thank you. Date: Tue, 29 Jul 2014 15:39:04 +0000