CSA C873 Building Energy Estimation Methodology - A simplified monthly calculation for quick building optimization

Abstract

CSA C873 Building Energy Estimation Methodology (BEEM) is a new series of (10) standards that is intended to simplify building energy calculations. The standard is based upon the German DIN Standard 18599 that has 8 years of proven track record and has been modified for the Canadian market. The BEEM method relies on steady state heat balance equations using monthly averages instead of dynamic equations used in hourly software. The method then relies on utilization factors to calculate the contribution of heat gain on heating loads and includes a simplified algorithm for lighting savings associ-ated with daylight strategies. The daylight algorithm is based on avail-able climate data and detailed daylight modelling. The method was validated through the modelling of seven building archetypes in 6 dif-ferent climate zones. Results from the BEEM modeling is compared to similar buildings modeled in CanQuest. Seven typical building ar-chetypes were modeled in 6 different Canadian climate zones. These archetypes are different than the ASHRAE 140 or the BESTEST models with more zones defined and different HVAC systems. The in-tent was to compare the method for typical simple Canadian commer-cial buildings. An average of 8.5% difference on the overall energy consumption was found. Acknowledging there is a difference between energy modeling software results, this difference needs to be put in perspective with differences between energy modeling software and difference from energy modelling to real building consumption. BEEM has the advantage of offering a direct feedback to the user al-lowing for a real time optimization process. The intent of this method is to provide a tool for simple buildings that usually don't get modeled. The BEEM method is not intended as a replacement for the more de-tailed energy modelling simulation that is typically performed for larger or more complex buildings. The planned release date for the standard is March 2014. The CSA C873 Building Energy Estimation Methodology task force is considering the development of a software tool to assist with the adoption of BEEM for simple projects. The Na-tional research Council – Canadian Codes Centre is considering the standard as a path for demonstrating compliance with the National Energy Code for Buildings in 2015