Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy Life-cycle approach to the estimation of energy efficiency measures in the buildings sector Sara Abd Alla, Vincenzo Bianco ⁎ , Luca A. Tagliafico, Federico Scarpa University of Genoa – DIME/TEC, Division of Thermal Energy and Environmental Conditioning, Via All'Opera Pia 15/A, 16145 Genoa, Italy HIGHLIGHTS • Embodied energy impact on the energy life cycle analysis of buildings is assessed. • Energy and carbon pay-back largely vary if the embodied values are considered. • Embodied energy plays a critical role on the estimation of wall insulation. ARTICLEINFO Keywords: Embodied energy Life cycle analysis Energy efficiency Payback period ABSTRACT The implementation of energy efficiency measures is an effective way to gain energy savings in the Italian residential sector. This paper assesses the embodied energy impact related to the envelope insulation and evaluates the energy and carbon payback of the efficiency measures. The proposed method consists of (1) an estimation of the baseline operational energy consumption, (2) simulations of realistic retrofit solutions and, (3) the assessment of the ‘retrofitting’ embodied energy and the energy and carbon payback time calculation. The payback is based on the comparison between the saved operational energy and the embodied energy of the materials selected for insulation. Ten Italian cities are analysed, and the results show a deep dependence on the climate zone. In Northern Italian cities, envelope insulation gains relevance as the energy and carbon payback periods are shorter, about 3 years against the 84 years for the Southern city of Palermo. The optimal thickness is estimated for the city of Milan considering the building’s typology, the insulation materials, and the energy payback. This study shows how the total energy savings can be used as a criterion to obtain design indications. 1. Introduction Retrofit measures can significantly reduce operational energy con- sumption in winter and summer climatization and improve the effi- ciency of existing buildings. To this aim, Mirabella et al. propose a wide literature review [1] on research efforts to analyse the environmental impacts of strategies for improving energy efficiency. The review highlights the relevance of considering building materials and equip- ment during the entire life cycle of buildings. Their findings show how the impact of the renewable systems’ embodied energy is neglected in most of the decision-making processes mainly for the difficulty in ob- taining detailed information. In fact, since new materials require manufacturing and transportation, the retrofit process inherently leads to an increase in the embodied energy of the whole building and needs to be included in the life cycle assessment [2]. New buildings’ projects need a careful evaluation in the materials selection phase to balance embodied energy with factors as climate, availability of materials and transport costs [3]. Similarly, in existing buildings, the implementation of energy efficiency measures that reduce operating energy consump- tion have a relevant embodied energy contribution and need to be in- cluded in the life cycle assessment [4]. In this context, Hong et al. propose a multi-dimensional input- output framework to examine which provinces and supply chain stages contribute most to the embodied energy of the building sector [5]. In line with this, a multi-regional input-output analysis is applied by Liu et al. [6] to understand the global consumer countries and the sectorial interactions concerning the energy embodied in the production of construction goods and services. Besides, Stephan and Stephan [7] propose a cost structure of energy consumption in each of the phases of the life cycle including embodied, transportation and operational en- ergy. Chau et al. [8] analysed the “end of life” management strategies for a building and concluded that materials’ recycling is the most https://doi.org/10.1016/j.apenergy.2020.114745 Received 12 December 2019; Received in revised form 20 February 2020; Accepted 25 February 2020 ⁎ Corresponding author. E-mail addresses: vincenzo.bianco@unige.it, vbianco@libero.it (V. Bianco). Applied Energy 264 (2020) 114745 Available online 05 March 2020 0306-2619/ © 2020 Elsevier Ltd. All rights reserved. T