Building Energy Efficiency from the First Decisions
David Eijadi, Prasad Vaidya, Chris Baker | 2011
This paper illustrates the energy savings potential embedded in early design decisions for 61 commercial U.S. projects that participated in new construction energy efficiency programs in 2009 and 2010. When energy modelling is used solely to determine how much better than the energy code a particular design is, some opportunities for real energy savings are lost. The modelling protocols of the major energy codes require that each unique design be compared to a corresponding unique baseline. As a result, design alternatives are rarely compared with each other. In some situations, the modelling protocols in these codes actually promote design alternatives with higher absolute energy use for early design decisions. Four utilities in the United States have implemented new construction energy efficiency programs that mitigate this problem by affecting design decisions using contiguous simulations models from the pre-design stage through initial occupancy. These early design decisions are important because they affect the energy use of the building throughout the life of the building. Early decisions that affect energy use, such as building shape or window area, are more persistent than lighting or mechanical efficiency strategies employed later in the design process. Over the life of a building, the lighting system and mechanical system will be replaced several times, but the overall building shape and fenestration will remain unchanged. Consequently, even a 5% to 10% annual energy use difference from an opportunity missed early in design has a large effect over 50 or 100 years. This paper also provides policy recommendations that could better support decisions early in the design process that maximize energy savings so that the code recognizes and credits comprehensive whole-building performance for early decisions.