The Energy Performance Gap - A Swedish Perspective

Abstract

Literature reviews from different countries show that the difference between the calculated and measured energy use of the building, often known as “energy performance gap”, can be as high as 100-200%. Knowing the size of the building energy performance gap, if it exists, along with its underlying causes will enable professionals to make more informed assumptions and produce better predictions. As there aren't many studies conducted in Sweden, more in-depth research is required to fully examine the energy gap and its causes. The causes for an energy performance gap can be estimated by comparing the calculated data with the measured energy use of the building. However, obtaining the data needed for simulations and real measurements is quite complicated, as it is never readily available.

In this master’s thesis, an approach is made to identify the presence of an energy performance gap in Sweden, and if so, the significance of the problem in relation to Swedish regulations and current practices in the field. The research started by analysing the literature review to have a deeper understanding on the topic. Subsequently, necessary data were collected, including metered energy data from property managers, energy declaration certificates from Boverket database, and energy calculations from consultants, to be compared to assess whether there is an energy performance gap at a primary level analysis. Although the available data for this part was not sufficient (almost 30 buildings) to compute the extent of the gap in Sweden, the results suggest the existence of a gap.

The next part of the study involved conducting meetings with 28 professionals with expertise in the field of building energy. They provided valuable feedback and observations on the possible causes of the energy performance gap in a Swedish context. The chosen professionals included consultants, certified energy experts, researchers, contractors, and a building inspector from a municipality. Nearly all professionals confirmed the existence of an energy gap and presented various reasons behind the causes, which included, proper system optimization, hot water circulation losses, inaccuracy of input data during design calculations, the impact of occupant behavior, lack of proper submetering in buildings affecting the system maintenance and error detection, inaccurate energy declaration calculation methods, enough knowledge and competence, lack of communication and need for a feedback loop to the consultants, faults during construction and budget constraints.

The final part of this research intended to investigate possible causes for a gap by analyzing the impact of different factors contributing to the energy performance gap through an intensified case study. This involved calculations and analysis of the measured energy data of a residential building. The objective was to identify the major causes and their impacts on the energy performance gap. The details of the building, including the measured data from submeters were provided by Fojab Arkitekter. First, the calculations and energy simulations for the base case were done to match the design requirements and the Swedish regulations. Then a specific set of parameters were altered according to the feedback from professionals of the earlier part of the study. The parametric simulation was done on IDA ICE to investigate the influence of different parameters on the energy use in comparison to available measured energy data. The parameters chosen included hot water use and circulation losses, heating setpoint, occupancy patterns along with others that impact the efficiency of the building envelope. The parametric simulation resulted in 1944 different possible results. These were deeply analyzed to assess the magnitude of each individual parameter on the building efficiency. The highest impact was observed when varying the indoor heating setpoint even by just 1-2 ˚C. This matched the experts’ feedback on this matter and highlighted the importance of proper system optimization for better energy efficient buildings.

The findings of the thesis suggest the presence of an energy performance gap, yet its magnitude requires comprehensive statistical analysis. The outcomes of this study can aid professionals engaged in both new constructions and building renovations by enhancing design and focusing on factors that contribute to the energy performance gap. The conclusion emphasizes the importance of communication among stakeholders and clear contract clauses to ensure energy goals are met, alongside focusing on proper system optimization post-occupancy. The study highlights the significance of updating reference input data required for calculations. The normalization process in Sweden is also discussed, noting its effectiveness but also highlighting challenges related to energy meter sufficiency and the lack of calculation method standardization. The conclusion emphasizes the dynamic nature of building energy consumption and the importance of accurate predictions to achieve Sweden's carbon neutrality target.

Popular Abstract

Do Swedish buildings fall short in terms of energy efficiency? Bridging the energy performance gap
Does the real energy performance of buildings match the calculation carried out when they were designed? If not, why isn’t the performance as designed/predicted? The difference between the calculated and measured energy is called the “energy performance gap”. In this study we delve into this from a Swedish perspective through literature review, data collection, professional consultations, and a case study. The results suggest an energy performance gap in Sweden influenced by multiple factors, emphasizing the need for improved data accuracy, stakeholder communication, and system optimization to enhance building energy efficiency.
The efforts to produce energy efficient buildings are hampered by an energy performance gap which has multiple causes. This makes it crucial to understand how actual building performance compares to predicted or calculated performance. In this study, we tried to engage with professionals from different areas of expertise, including consultants, energy experts, and property developers, to get their perspective on the discrepancies between calculated and actual energy usage in buildings. By running a building simulation for a case study and altering different parameters this aligned with conducting in-depth interviews, we tried to understand the underlying causes of this energy performance gap.
From interviews with 28 professionals working in Sweden, some of the reasons behind the energy performance gap were identified, the key causes being hot water circulation losses, insufficient optimization, lack of proper communication, inaccuracies in input data during design calculations, occupant behavior, among others. This highlighted the need for better communication and coordination among stakeholders throughout the building lifecycle, from design to post-occupancy maintenance, as the responsibility of an energy efficient building lays on all the people involved. A case study was conducted on a residential building to see how these factors influence the energy use of the building, which showed that the energy use of a building hugely varies depending on the input data chosen.
The exact magnitude of the gap in Sweden requires detailed and a large-scale statistical analysis. However, the reasons and solutions identified in this study remain relevant for minimizing this gap. The findings from this research can help professionals in both new construction and building renovations by enhancing design and focusing on factors that contribute to the performance gap. Accurate identification and reduction of the energy performance gap can inform building design practices, regulatory frameworks, and maintenance strategies, leading to more energy-efficient buildings. The research findings can be used to refine energy calculation methods, improve the accuracy of energy performance certificates, and guide the placement of energy meters for better data collection and system optimization. The results also show that for better energy efficient buildings, it’s the responsibility of all building stakeholders, starting from the consultant to the contractor on site and finally to property managers ensuring proper system optimization.

• author: Bandak, Asala and Sreenivasan, Athira
• supervisor: Pieter de Wilde; Akram Abdul Hamid
• organization: Department of Building and Environmental Technology; Division of Energy and Building Design
• course: AEBM01 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Energy Performance Gap, Buildings Energy Efficiency, IDA ICE, Energy declarations, Energy Performance certificates, Building Energy Simulation.
• language: English
• id: 9158682
• date added to LUP: 2024-06-10 07:33:16
• date last changed: 2024-06-10 07:33:16