ENERWIN PRO© is a Windows-based hourly energy simulation model for evaluating whole-building energy performance. The program features an interactive graphical interface for input and output. The simulation model uses algorithms that permit hour-by-hour energy calculations in minimal time. The program’s tabular results include monthly and annual utility energy and costs, peak HVAC loads, a thermal comfort analysis and a life-cycle cost summary. It has a Visual Basic interface and a FORTRAN-95 simulation engine that features transient modeling based on sol-air temperature, time lag, and decrement factor; zone loads and temperatures based on a thermal balance methodology; and daylighting saving algorithms based on a modified Daylight Factor methodology. The software contains default data bases populated with weather data for over 4700 cities in 186 countries worldwide, lighting power densities based on 40 building types in ASHRAE’s energy-efficiency Standards 90.1 and 189.1. The latest version, Enerwin-10 lets the user select from three different standards (90.1-2010, 90.1-2016, or the Standard 189.1-2014 for Green Buildings.) Enerwin-EC is similar but is based mostly on U-Factor requirements from Standard 90.1-2007. Version 10 adds significant precision in selecting the default wall and roof U-factors and window solar heat gain coefficients (SHGC), in that these are now sensitive to not only the building type selected, but also the particular code selected and the climate zone represented by the selected city. Ventilation rates, as well as occupancy densities, are based on the ASHRAE Standard 62.1-2010 for acceptable indoor air quality. Occupancy and other 24-hour profiles, such as lighting and hot water usage, are based on sources that have been involved in energy simulations for buildings, particularly the U.S. DOE and the COMNET (Commercial Buildings Energy Modeling Network) organizations. Enerwin-10 has three separate schedules (“Mon-Fri”, “Sat”, and “Sun”) for each building type and for each of the usage parameters (occupancy, hot water use, lighting, receptacles (plug loads), fans and ventilation, summer thermostat settings, and winter thermostat settings.) Both Versions 10 and EC include the calculation of greenhouse gas emissions caused by the building’s energy consuming systems. If gas or oil are used for on-site heating, the emissions are calculated directly from the fuel consumption. Emissions for all electricity use are calculated at the power plant, showing values for gas-fired, oil-fired, and coal-fired generators. Emissions are calculated in terms of tons (short or metric) of Carbon Dioxide (CO2), Sulphur Dioxide (SO2), and Nitrous Oxides (NOx). At the end of each run, the user can view results in tabular or graphic (e.g., barcharts and graphs). In tabular form, the user can choose to see results in Microsoft Excel© (automatic links) that can include all hourly data in all buildings zones, as well as hourly weather data including sun angles and solar insolation on horizontal and vertical surfaces. All runs can be saved for future printing and or reviews and reruns.