The largest source of energy consumption and greenhouse gas emissions in Canada and around the world is buildings. As a consequence, building designers are encouraged to adopt designs that reduce operational energy, through both increasingly stringent energy codes and voluntary green building programs that go beyond code requirements. Among structural building materials, wood has by far the lowest heat conductivity. As a result it is typically easier to meet certain insulation targets (e.g., thermal transmission and effective thermal resistance) with wood-based wall systems when following current construction practices. Good envelopes greatly contribute to energy efficient buildings. However, there are many factors in addition to building envelope insulation levels that affect the operational energy of a building. This study aims to provide designers with information which will assist them to choose energy efficient exterior wall systems by providing energy consumption estimates for an archetypal 6-storey residential building. Comparisons were made among several exterior wall systems including light wood-framing, cross-laminated timber (CLT), steel-stud framing, and window walls, for a range of structural systems including structural steel, light wood-frame, CLT, heavy timber, and concrete. The opaque exterior wall assemblies targeted meeting the minimum thermal requirements based on the National Energy Code of Canada for Buildings (NECB. NRC 2011). A 3-D method was used to calculate effective R-values of these exterior walls by taking into account all thermal bridging, in comparison with a parallel-path flow method in compliance with the NECB. Three glazing ratios, including 30%, 50%, and 70%, and two efficiency levels for Heating, Ventilation, & Air Conditioning (HVAC) systems, termed basic HVAC and advanced HVAC, were also assessed. Whole-building energy consumption was simulated using EnergyPlus. Four climates, from Zone 4 to Zone 7, with cities of Vancouver, Toronto, Ottawa, and Edmonton to represent each climate, were selected in this study. The energy assessment was conducted by Morrison Hershfield.
