In their quest for deeper energy savings, many projects expand building enclosure energy conservation measures (ECMs) opportunities beyond HVAC and lighting systems energy savings. The Air Infiltration Reduction Research demonstrates cost effective means to increase the energy savings through air infiltration reduction beyond Code. The team included National Grid’s Strategy Group, SMMA’s Sustainability & Energy Group and ICF.  The research included application of air infiltration testing standards and methodology in support of advanced air infiltration reduction design and construction best practices. The energy savings were measured through whole building enclosure air tightness testing on 5 multi-family facilities, while assessing the feasibility of developing an energy conservation measure [ECM], informing its potential application to utility Multi-Family, Commercial and Institutional (C&I) incentives programs supporting additional building types.