year, expressed in kWh/(m2·year). Total Energy Use Intensity: The modelled amount of total energy used by a building, per unit of area, over the course of a year, expressed in kWh/(m2·year). Airtightness metrics Air Changes per Hour at a 50 Pa Pressure differential, as measured by a blower door test. Air Leakage Rate: A measure of the rate that air leaks through the building envelope per unit area of the building envelope, as recorded in L/(sm2) at a 75 Pa pressure differential. Requirements To meet the requirements of the BC Energy Step Code, builders will work with an energy advisor to check that their plans will meet the energy-performance requirements of a given step. An energy advisor uses software to analyze construction plans and determine the energy efficiency of a building. The builder then begins construction, paying special attention to the building envelope—the walls, windows, doors, and insulation. The energy advisor also tests a building once it is built to see how well it performs. To achieve the Lower Steps, building and design professionals and trades can rely on conventional building designs with careful air-sealing practices, and incrementally incorporate some key elements in the design, building envelope, and equipment and systems. Builders and designers will collaborate with the energy advisor to select the most cost effective way to meet the standard's requirements. These Lower Steps give builders new flexibility in how to achieve modest gains in efficiency through improved envelopes and/or upgraded systems. To achieve the Upper Steps, builders and designers will need to adopt an integrated design approach to building design and may need to incorporate more substantial changes in building design, layout, framing techniques, system selection, and materials. These techniques and materials will be more costly and challenging without additional training and experience. Origins In September 2015, the province's Building Safety and Standards branch established an Energy Efficiency Working Group (EEWG) to review policies and regulations that apply to energy efficiency in BC, to seek stakeholder input and offer guidance on how to best implement an Energy Step Code to achieve consistent building energy performance beyond the BC Building Code. The consultations engaged with the building and development sectors, and the trades and professions that support them, as well as local governments, utilities, and other stakeholders, to identify a consistent approach to increasing energy-efficiency standards. In August 2016, the group renamed itself the Stretch Code Implementation Working Group