This document presents a methodology for assessing baseline energy efficiency in new single-family residential buildings and quantifying related savings potential. The approach was developed by Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy (DOE) Building Energy Codes Program with the objective of assisting states as they assess energy efficiency in residential buildings and implementation of their building energy codes, as well as to target areas for improvement through energy codes and broader energy-efficiency programs. It is also intended to facilitate a consistent and replicable approach to research studies of this type and establish a transparent data set to represent baseline construction practices across U.S. states.