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Today, the building sector is responsible for about 40% of total energy consumption, both at National and European level (European Commission, 2012). Furthermore, based on Eurostat data (European Commission, 2014), average energy consumption in the non-domestic sector is estimated to be at least 40% higher than in the domestic sector. At the same time, in the non-domestic sector, significant variations in energy consumption are reflected due to the different geography or type of building. These differences are highlighted in Figure 1, which shows the distribution of energy consumption between offices, educational buildings, hospitals, hotels and restaurants and sports facilities for the EU.
It is evident that office buildings represent more than 25% of energy consumption, resulting in a heated debate on the need for energy saving (European Commission, 2016).
However, before any debate on the need for energy savings, an investigation of the causes leading to this obligation must be preceded first. To understand how a building really consumes energy, the dominant approach has to be overcame, as it indicates that “theoretical models may assess the energy efficiency of buildings on the basis of the intrinsic characteristics (building shell) and static data (heating modeling, ventilation, lighting, etc...)”. This view is widespread nowadays using energy simulation tools and is the basis for assessing the energy efficiency of buildings in both Greece (Dascalaki, 2012) and Europe with the EPCs (Energy Performance Certificates) (EN 13790, 2008, EN 15217, 2007).
Figure 1. Building Sector Consumption in the EU
Different studies demonstrate that the use of simulation tools for calculating energy efficiency is not sufficient, since the conditions of actual operation and the interaction of end users with it are not considered. Most of the energy consumption in public buildings during all stages of the life cycle occurs during their operational phase and represents 80% of total consumption (Kamat et al., 2013). Within this rate, at least 70% is due to the behavior of end users and their decisions taken in real time (Delzendeh et al., 2017).
End-user behavior is a determining factor contributing to the use of energy either directly or indirectly by opening/closing windows, activation & deactivation or reduction of lighting, activation & deactivation of office equipment, air conditioning and heating systems, etc. Moreover, user behavior is one of the most important sources of uncertainty in predicting the use of energy through simulation due to complexity and inherent uncertainty (Paone et al., 2018, Martinaitis et al., 2015, Hong et al., 2015, Wang et al., 2015, Page et al., 2008).
On the other hand, an important aspect contributing to the volatility of energy consumption in buildings is the management of the activities carried out in the building. Business processes (organization and management of procedures) are an integral part of the operating procedures, representing more than 30% of total energy consumption (Lopez 2014). Various studies have shown that the measurement of energy consumption in buildings is highly unstable even between buildings with the same function located in a similar geographical environment. Among various factors contributing to this variability is the behavior of end-users in the business processes performed in the building (European Commission 2012, Keyvanfar et al, 2014, Rasfanjani et al., 2016, Hoes et al., 2009).
Parallel to, and beyond business processes, emphasis is also placed on end-user comfort conditions in conjunction with energy consumption. Different studies show, that given the modern trend towards low-energy buildings, it is imperative that end-users are actively involved in achieving the high energy efficiency targets, without reducing their comfort or productivity though (Nicol 2002, Liu 2012, Jang 2016, Shaikh 2014).