R.H. Crawford and A. Stephan (eds.), Living and Learning: Research for a Better Built Environment: 49 th International Conference of the Architectural Science Association 2015, pp.423–433. ©2015, The Architectural Science Association and The University of Melbourne. The next step in energy rating: the international ETTV method vs. BCA Section-J Glazing Calculator Mehran Oraee and Mark B. Luther School of Architecture and Built Environment, Deakin University, Geelong, Australia moraeena@deakin.edu.au, mark.luther@deakin.edu.au Abstract: The most important prevention in minimizing energy transfer in commercial buildings is the treatment of glazing in the building facade. In a commercial building, while the impacts of roof, walls and floors on the overall heating and cooling loads of the building have low effects, glazing is likely to be the most important factor. This paper investigates the BCA Section-J glazing calculator and the ETTV (Envelope Thermal Transfer Value) methods and tries to look for differences as well as similarities in calculation of building envelopes energy performance. For this investigation, a hypothetical high-rise commercial building in Melbourne, Australia is considered when evaluating the energy performance of the envelope through these two methods. Both methods consider the U-Value of glass and wall materials as well as Solar Heat Gain Coefficient (SHGC) and Shading Coefficient (SC) of the glass. Findings in this research project indicate differences and significant discrepancies between the BCA Section-J and ETTV methods in evaluating the energy performance of commercial building façades. Issues of calculation weaknesses are identified with the lack of air leakage and infiltration of a particular façade design or window to wall ratio (WWR). Suggestions have been made where improvement to the overall energy calculation through facades of a commercial building is needed. Keywords: ETTV method, BCA Section-J, envelope energy performance, glazing. 1. Introduction Sustainable development and environmental protection are among the major motivations of energy conservation initiatives. Energy efficiency is universally known as one of the most cost effective ways to reduce related building energy issues (Hodges, 2005). Since buildings are significant energy consumers in many countries, energy use in buildings has become a policy issue worldwide to increase energy efficiency of buildings. Particularly in commercial and high-rise buildings, energy efficiency is a concern and means to improving both the performance of HVAC systems and the mechanisms of heat transfer through the building envelope are crucial (ABCB, 2010). While, in commercial buildings, the impacts of roof, walls and exposed floors on building’s overall cooling or heating load are generally small, glazing is likely to be the most important factor. Although other factors such as efficiency of HVAC systems and