The National Energy Audit Tool (NEAT) is one of two energy audits provided under the Weatherization Assistant umbrella. The Weatherization Assistant is a user-friendly, advanced energy audit software tool developed by the Oak Ridge National Laboratory (ORNL). Designed for use specifically within the U.S. Department of Energy (DOE) Weatherization Assistance Program, it is also used by utility and other programs and home energy professionals to identify cost-effective energy conservations measures for homes. The Weatherization Assistant is a Windows-based software program. It serves as the umbrella program for NEAT for site-built single-family houses (also useable on small multifamily homes) and the Manufactured Home Energy Audit (MHEA) for mobile homes (MHEA was originally developed by the National Renewable Energy Laboratory and is now supported and maintained by ORNL). Both audits analyze the applicability and cost effectiveness (i.e., savings-to-investment ratio or SIR) of over 45 envelope, equipment, and baseload weatherization measures. The audits use a variable-based degree-day method and take into account local weather conditions, retrofit measure costs, fuel costs, specific construction details of the home, and the interaction in energy savings between measures when multiple measures are installed as a package. Utility bills can be entered to calibrate the house model and adjust the savings estimates. In addition, the Weatherization Assistant provides expanded optional capabilities that are useful in implementing and administering weatherization programs related to agency-related contact information, client data intake, health and safety issues, diagnostic measurements, work orders, status tracking, simplified cost accounting, inventory control, report generation, site mapping, and digital photo storage.