Tierra staff completed both an impact and process evaluation of Puget Sound Energy’s (PSE) Duct Sealing & Repair (Duct Ninja) Program for the 2009-2010 program cycles. The primary objective of this study was to determine the energy savings associated with duct system repairs conducted from a unique prescriptive duct sealing approach. A secondary objective involved assessing opportunities and areas of improvement in future program iterations. A billing analysis of pre-/post-Duct Ninja home energy consumption estimated savings attributed to prescriptive duct system repairs. Tierra staff members calibrated this model to adjust savings for variations in site characteristics, including home type, home vintage, heating system type, and gas consumption.