Citation: Al-Sakkaf, A.; Bagchi, A.; Zayed, T. Evaluating Life-Cycle Energy Costs of Heritage Buildings. Buildings 2022, 12, 1271. https:// doi.org/10.3390/buildings12081271 Academic Editor: Elena Lucchi Received: 30 June 2022 Accepted: 17 August 2022 Published: 19 August 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). buildings Article Evaluating Life-Cycle Energy Costs of Heritage Buildings Abobakr Al-Sakkaf 1,2, * , Ashutosh Bagchi 1 and Tarek Zayed 3 1 Department of Building, Civil and Environmental Engineering, Concordia University, Montréal, QC H3G 1M8, Canada 2 Department of Architecture & Environmental Planning, College of Engineering & Petroleum, Hadhramout University, Mukalla 50512, Yemen 3 Department of Building and Real Estate (BRE), Faculty of Construction and Environment (FCE), The Hong Kong Polytechnic University, ZN716 Block Z Phase 8 Hung Hom, Hong Kong, China * Correspondence: abobakr.alsakkaf@concordia.ca; Tel.: +1-5144311929 Abstract: After the sustainability of heritage buildings (HBs) has been evaluated and it is determined that rehabilitation is needed, then the life-cycle cost (LCC) of energy for HBs can be analyzed. The objective of this research was to evaluate the LCC of energy for HBs and develop a comprehensive life-cycle model that will aid in expenditure planning and budget allocation. This study was validated through the weighted sums method and two case studies—Murabba Palace (MP), Saudi Arabia; and Grey Nuns Building (GN), Canada—were evaluated. For any HB, the project life cycle includes planning, manufacturing, transportation, construction, operation, and maintenance phases. Saudi Arabian and Canadian experts completed questionnaires to attribute a percentage of importance of each of the aforementioned phases with respect to energy consumption. The findings from this study will enable facility managers to make effective rehabilitation decisions. The operation phase has the highest impact on the energy consumption, gas consumption, and cost of the building in both case studies. Moreover, the findings from this study can be used to establish cost-effective intervention strategies. Their responses were employed in the development of a life-cycle model. Excel ® and Minitab ® were used to calculate Cronbach’s alpha values for data reliability, and the project LCC of energy for the two case studies was studied. The operation phase appeared to be the most energy-consuming phase in both case studies, contributing the most to the cost of the building. Keywords: heritage buildings; rating system; digitalization; energy; simulation; LCE 1. Introduction Heritage buildings are part of human creation, which produces icons for a country, provides local identity, reflects the cultural values and background, represents a source of memory, historical events, and also contributes to the tourism business industry [1]. The buildings contribute significantly to global energy and water consumption. They also account for about two-fifth of global greenhouse gas emission and solid waste gen- eration [2–6]. Increasing the sustainability of buildings will help in decreasing energy consumption, greenhouse gas emissions, and air pollution; improve the health and living conditions of occupants; and increase productivity and employment rate [4,7]. There- fore, it is imperative to accurately determine the sustainability of buildings, and for this, sustainability-rating tools are needed [8,9]. The UK, for example, follows the Standard Assessment Procedure (SAP) to calculate buildings’ energy performance. On a scale of 1 to 100, SAP measures the efficiency of the thermal and heating systems in a building [10]. Based on the SAP results presented by the UK government in 2006, the energy performance of older buildings proved to be much lower than that of the more recent ones. To put it into perspective, the SAP rating of more than 40% of buildings constructed prior to 1919 was less than 41, whereas the rating of most buildings built in 1990 was over 70 [11]. Despite the intuitive results, several Buildings 2022, 12, 1271. https://doi.org/10.3390/buildings12081271 https://www.mdpi.com/journal/buildings