The Simulation of a Zero-Energy Residential Building for the Solar Decathlon Competition

In 2002, the Department of Energy (DOE) sponsored the world’s first university competition to design and build a completely solar powered house. One requirement of the competition was to perform simulations of the house’s photovoltaic, solar thermal, and space conditioning systems. By instituting this requirement, DOE is encouraging the building industry to apply the “whole-building design” approach to residences as a method of reducing financial and environmental operation costs of the building over its lifetime. This paper describes the simulation approach taken by the University of Colorado Solar Decathlon Team. In addition to describing the process of simulating a zero-energy residential building, the specific results of the simulations and related parametric studies are also presented. The design and analysis process provides a case study in the application of six different simulation tools for zero-energy building design. Energy-10 provided an environment for parametric analysis of building design options during the critical early design phase. However, it lacks the flexibility to model solar electric, solar thermal, and specialized HVAC systems. FChart gave valuable guidance early in the project on the impact of solar system sizing and performance. TRNSYS is extremely flexible in that it can simulate various solar systems and the interactions of virtually any thermal system commonly found in buildings. This flexibility is accompanied by the burden of complexity and a generic user interface that limits its use as a routine building design tool. Radiance, AGI32, and ECOTECT provided specialized simulation tools for the integration of the daylight delivery system, external shading devices, and the electric lighting system. Additional development is required to better integrate these design needs into general building energy analysis tools.