EnergyPlus is a computer program that models heating, cooling, lighting, ventilating, and other energy flows in commercial and residential buildings. The program’s development, led by the Lawrence Berkeley National Laboratory, was a collaborative effort between Penn State, the University of Illinois, the U.S. Army’s Construction Research Laboratory, the Department of Energy’s Office of Energy Efficiency and Renewable Energy, the Florida Solar Energy Center, Oklahoma State University, the University of Wisconsin, and GARD Analytics, Inc.

Dr. William Bahnfleth directed the creation of the program’s modules for simulating heat transfer in basements and slab-on-grade foundations. Bahnfleth’s research team included graduate students, M.S. candidate, Edward Clements and Cynthia Cogil (M.S. ’98) who used their portions of the work as thesis projects.

Most building thermal simulation programs model foundation heat transfer by applying fairly crude approximations of ground temperature to one-dimensional models of basement walls and floor slabs. Bahnfleth’s software greatly improves the accuracy of foundation heat transfer estimates by performing three-dimensional simulation of the foundation and surrounding soil, including a detailed ground surface energy balance.

The EnergyPlus program can be used by engineers, architects, and researchers for building design, energy code compliance and green building certification, amoung other things. It can also be used to calculate indirect environmental effects, such as the generation of atmospheric pollutants that are associated with a building’s energy use. Use of DOE-2, a predecessor to EnergyPlus, is estimated to have saved $20 billion in energy costs since 1980. EnergyPlus is expected to exceed that performance during the next decade.

EnergyPlus can be downloaded for free from the Department of Energy’s web site at www.eere.energy.gov/buildings/energyplus. More than 12,000 people have downloaded the software so far. Bahnfleth notes that the program currently lacks a user-friendly graphical interface, but interfaces are under development and should be available soon.