The U.S. Department of Energy (DOE) Building Energy Codes Program supports the upgrade and implementation of building energy codes and standards, which set minimum requirements for energyefficient design and construction for new and renovated buildings, and impact energy use and greenhouse gas emissions for the life of buildings. Continuous improvement of building energy efficiency is achieved by periodically updating model energy codes for commercial and residential buildings. Through consensus-based code development processes, DOE recommends revisions and amendments, supporting technologically feasible and economically justified energy efficiency measures. Ensuring that model code changes impacting the cost of building construction, maintenance, and energy services are cost-effective also encourages their adoption and implementation at the state and local levels. Pacific Northwest National Laboratory (PNNL) prepared this analysis to support DOE in evaluating the energy and economic impacts associated with updated codes in commercial buildings. The purpose of this analysis is to examine the cost-effectiveness of the 2013 edition of ANSI/ASHRAE/IES 1 Standard 90.1 (ANSI/ASHRAE/IES 2013). Standard 90.1 is developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard Standing Project Committee (SSPC) 90.1. It is the model energy standard for commercial and multifamily residential buildings over three floors (42 USC 6833). PNNL analyzed the cost-effectiveness of changes in Standard 90.1 from 90.1-2010 to 90.1-2013, as applied in commercial buildings across the United States. During the development of new editions of Standard 90.1, the cost-effectiveness of individual changes (addenda) is often calculated to support the deliberations of ASHRAE Standard Standing Project Committee (SSPC) 90.1. The ASHRAE process, however, does not include analysis of the cost-effectiveness of the entire package of addenda from one edition of the standard to the next, which is of particular interest to adopting State and local governments. Providing States with an analysis of costeffectiveness may encourage more rapid adoption of newer editions of energy codes based on Standard 90.1. This information may also inform the development of future editions of Standard 90.1.To establish the cost-effectiveness of Standard 90.1-2013, three main tasks were addressed:• Identification of building elements impacted by the updated standard • Allocation of associated installation, maintenance, and replacement costs • Cost-effectiveness analysis of required changes In addition to installation, maintenance, and replacement costs, energy cost differences were needed to determine cost-effectiveness. The energy costs for each edition of Standard 90.1 were determined previously under the development of Standard 90.1-2013, as described below.The current analysis builds on the previous PNNL analysis (as outlined in Section 5.2) of the energy use and energy cost saving impacts of Standard 90.1-2013 compared to pre...