Accuracy of Code Compliant Design-Stage Building Energy Performance Simulation Models

Curbing energy usage in new commercial buildings has become a common theme within mandated standards adopted by many states of the US. Since 1975, when ASHRAE first published its Energy Standard for Buildings following the first oil crisis [1], focus has been placed on the energy efficiency of buildings during the design and construction phases. Most of these standards attempt to allow the buildings designers flexibility in how compliance can be demonstrated. ASHRAE 90.1 [2], has been adopted by many states in the US and is the most common of the national energy conservation standards for commercial buildings. It is also used as a benchmark for many country’s national standards such as the Middle East, Africa and Asia. 90.1 has been updated on a continuous maintenance basis starting in 2001. Since then the standard has re-issued in revised form every three years following the evolution of more efficient equipment and building technological advances. Certain states, whilst following the general guidance offered within ASHRAE 90.1, compiled their own standards, such as California’s Title24, which is administered by the California Energy Commission (CEC). Title24 is effectively a version of 90.1, but with different parametric thresholds to achieve compliance. Although the two codes are developed separately, a fair amount of synergy and similarity exists [3].