One of the most significant barriers for achieving the goal of substantially improving energy efficiency of buildings is the lack of knowledge about the factors determining the energy use. Also policies agreements about energy saving targets (e.g., Energy Performance of Buildings Directive of the EU) as well as agreements about limiting greenhouse gas emissions are based on a knowledge of building energy consumption, in which a complex array of factors, including the user/occupant behavior, play a significant role. There is often a significant discrepancy between the designed and the real total energy use in buildings. The reasons for this discrepancy are generally poorly understood, and often have more to do with the role of human behavior than the building design.
This discrepancy leads to misunderstanding and miscommunication between the parties involved in the topic of energy savings in buildings:
In fact, building energy consumption is mainly influenced by six factors: (1) climate, (2) building envelop, (3) building services and energy systems, (4) building operation and maintenance, (5) occupants’ activities and behavior and (6) indoor environmental quality provided. The latter 3 factors, related to human behavior, can have an influence as great as or greater than the former 3 ones. The user related aspects and behavior effects can be seen from the large spread in energy use for similar or identical buildings, but a distinction between the building related and the user related energy part cannot established. All six factors need to be investigated together to understand building energy consumption data. Detailed comparative analysis on building energy data, concerning the six factors mentioned above, would provide essential guidance in identifying energy saving potentials and opportunities.
A limitation of much current research is that it focuses only on the first three factors (climate, building envelope, building services and energy systems). All of the factors, including building operation, occupants’ activity and behavior, and indoor environmental quality, need to be analyzed using a combination of simulation and real measured energy consumption data. As the differences in indoor climate can also cause huge differences in energy consumption, it is important to gather data on the real indoor climate conditions (in addition to energy usage) to understand and interpret measured data on building energy consumption. Besides that, another pivotal problem is that there is lack of a scientific method to account for interactions between the six influence factors and energy use in a clear and thorough way, and to predict the expected energy use as well in the case of all the influence factor are taken into account.
In addition, the inconsistency in the terms related to building energy is also a surprisingly serious problem in our achieving understanding of factors affecting energy use in buildings. For instance, many research projects show information on building energy consumption in Europe for heating for residential and non-residential buildings in terms of kWh/(m2.a), but there is no way of knowing what the term kWh/(m2.a) means. Because it applies to both space heating and cooling and other end uses, we know that it includes both electricity and fossil fuel. For some countries and researchers, the results are likely to refer to final energy, ignoring the energy losses associated with the production of electricity. For other countries, kWh/(m2.a) will include fossil fuels with their efficiency of conversion to electricity. This is an approximation of primary energy units. The first is inappropriate to measure the effect of buildings on energy use. The second is vague and unclear. Hence, this explanation of the energy use data makes the analysis of the factors responsible for energy use impossible.