Vol.:(0123456789) 1 3 Clean Technologies and Environmental Policy https://doi.org/10.1007/s10098-018-1510-x ORIGINAL PAPER Energy rating system for climate conscious operation of multi‑unit residential buildings Isuru Gamalath 1  · Kasun Hewage 1  · Rajeev Ruparathna 1  · Hirushie Karunathilake 1  · Tharindu Prabatha 1  · Rehan Sadiq 1 Received: 23 October 2017 / Accepted: 19 February 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Residential sector accounts for 17% of domestic energy use and 14% of the greenhouse gas emissions in Canada. Improving the energy performance of the Canadian residential building stock is vital in achieving climate action goals. A comprehensive review of popular building energy rating systems noted their lack of life cycle thinking. The scope of the popular rating sys- tems is limited to operational performance, ignoring the condition of the assets. This paper proposes a condition assessment framework for the energy system of existing multi-unit residential buildings (MURB), which combines the concepts of asset rating and operational rating. Indicators were identifed to defne energy, environmental, economic, and asset performance of MURB. A life cycle assessment was conducted to quantify the overall environmental impacts of energy technologies from point of generation. A fuzzy logic-based approach was used to overcome the challenges due to data uncertainty and impreciseness. A case study was conducted for a residential building at UBC Okanagan, Canada. The weights at indicator level and category level were defned based on stakeholder consultation, while also considering diferent decision scenarios. A fuzzy rule-based approach was used to combine the diferent performance categories to obtain an overall condition rating. The results indicate that the performance of the case study building can be rated as “good” under operational, asset, and overall categories. The fndings of this research can be used to improve the asset and operational management strategies in existing buildings and can inform the key stakeholders during the operational phase of the buildings. Keywords Building energy ratings · Multi-unit residential buildings · Life cycle thinking · Fuzzy logic Introduction Urban population in Canada has increased from 69 to 82% during 1960–2014 (The World Bank 2016). Further, the population growth in urban areas (7%) has been higher than the overall population growth of the country (5.8%) during 2006–2011 (Statistics Canada 2011). High demand for hous- ing in urban areas and land availability has made multi-unit residential buildings (MURBs) popular (Statistics Canada 2016). Recent statistics show that the resulting Canadian urban development is more upwards than outwards, as MURBs continue to grow in order to cater the housing needs of the growing urban population (Statistics Canada 2016). MURB construction exceeded single-family detached house construction in 2012, based on the number of build- ing permits issued (Statistics Canada 2016). In Canada’s three largest metropolitan areas, more than 50% of the total residential constructions planned are MURBs (Statistics Canada 2016). MURBs have been popular due to a number * Kasun Hewage kasun.hewage@ubc.ca Isuru Gamalath imgamalath@gmail.com Rajeev Ruparathna rajeev.ruparathna@ubc.ca Hirushie Karunathilake hirushie.karunathilake@alumni.ubc.ca Tharindu Prabatha tharindu.prabatha@alumni.ubc.ca Rehan Sadiq rehan.sadiq@ubc.ca 1 School of Engineering, University of British Columbia (Okanagan Campus), EME4242-1137 Alumni Avenue, Kelowna, BC V1V 1V7, Canada