This session will explore both high level monitoring protocols and in-depth performance results of energy and indoor environmental quality measurement within PHIUS+ multi-family buildings to outline opportunities and lessons learned. The presentation team will discuss findings from a detailed monitoring study comparing two nearly identical affordable housing multi-family buildings in Chicago, one meeting EnergyStar® Multi-family requirements and the other PHIUS+ standards. Both energy efficient buildings reduce carbon emissions and strive to enhance health and comfort while limiting operational costs for their income-qualified tenants. The purpose of the monitoring protocol is to verify that the desired outcomes are being achieved, to at least detect problems in case they are not, and preferably to diagnose problems as well.