esidential building energy efficiency is becoming increasingly important in U.S. energy policy. Analyzing the effectiveness of potential energy efficiency improvements in the residential sector involves running whole building energy simulations for alternative building designs. Such analysis requires detailed building design characteristics including climate, fuel type, energy technologies, and design improvements. For broad studies of the U.S. residential sector, prototypical designs representing "typical" residential buildings are necessary to provide the basis for this detailed analysis. This report defines two prototype detached residential house designs based on the 2009 International Energy Conservation Code (IECC). These prototypes can be used as baselines from which to analyze homes built to older IECC codes as well as to estimate the energy savings and sustainability impacts from increasing residential building energy efficiency beyond current state energy codes. These prototypes can also be used as a framework for developing additional prototype designs.