Comparative study of the LEED AND ISO-CEN building energy performance rating methods

The use of LEED as a building sustainability rating method is well established in the US. In this paper we concentrate on the calculation of the score in the Energy and Atmosphere category of LEED, i.e. the LEED-EAc1 score. Its calculation is based on an adaptation of the ASHRAE 90.1 calculation method. This paper will argue that the approach is needlessly complicated and laborious because there are simpler, non-simulation based methods that may be equally adequate for the energy rating of a building. One such alternative is the normative EPC rating method, which is widely used in Europe based on the ISO-CEN standard 13970. Each building energy performance rating method has a distinct approach for the calculation of building energy efficiency. Many papers discuss the basis of the calculations and compare them on the merits of their methods. In this paper, we focus on whether the two systems achieve their objective and which system does a better job in rating building designs. This comparison of the two methods is not only based on a direct comparison of outcomes, but is also studied with the consideration of its true intent, the relative ranking of buildings against each other. Consequently we will less focus on the absolute differences between the outcomes of the two methods, which have been found to be 20% or less in the Energy Use Intensities (EUIs), but will focus on statistical tests to verify whether there is a significant difference in the building rankings resulting from the two distinctly different approaches.