I have used the same strategy. But raising the supply air volumes to the critical room above that required by your load simulation has the effect of raising the minimum air flow. That is what actually brings the percentage of OSA down. Raising the minimum stop on the VAV terminal unit that serves that room is probably the more correct way of handling this. Raising the minimum stop leads to re-heat to maintain room temperature which results in higher energy usage so watch your energy usage in your modeling runs and balance the re-heat need against higher OSA values. What will also help is to look at ASHRAE interpretation IC 62.1-2007-17. ASHRAE 62.1 does not require OSA in rooms that are not normally occupied. Terry L. Wohlgenant, CIPE, BEMP, LEED AP BD+C Mechanical Design | Senior Associate twohlgenant at dlrgroup.com DLR Group Architecture Engineering Planning Interiors o: 602-381-8580 6225 North 24th Street, Suite 250 Phoenix, AZ 85016-2042 dlrgroup.com | listen.DESIGN.deliver dlrgroup.com is newly renovated and expanded. Click. Explore. http://www.dlrgroup.com