Understanding the Reasons behind the Energy Performance Gap of an Energy-Efficient Building, through a Probabilistic Approach and On-Site Measurements

Pierryves Padey,Blaise Périsset,Kyriaki Goulouti,Guy Wagner,Sébastien Lasvaux

doi:10.3390/en14196178

Pierryves Padey, Blaise Périsset + Show 3 more

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https://doi.org/10.3390/en14196178

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Abstract

The performance gap, defined as the difference between the measured and the calculated performance of energy-efficient buildings, has long been identified as a major issue in the building domain. The present study aims to better understand the performance gap in high-energy performance buildings in Switzerland, in an ex-post evaluation. For an energy-efficient building, the measured heating demand, collected through a four-year measurement campaign was compared to the calculated one and the results showed that the latter underestimates the real heating demand by a factor of two. As a way to reduce the performance gap, a probabilistic framework was proposed so that the different uncertainties of the model could be considered. By comparing the mean of the probabilistic heating demand to the measured one, it was shown that the performance gap was between 20–30% for the examined period. Through a sensitivity analysis, the active air flow and the shading factor were identified as the most influential parameters on the uncertainty of the heating demand, meaning that their wrong adjustment, in reality, or in the simulations, would increase the performance gap.

Highlights

The rising of the green building concept has been introduced as a solution to the mitigation of the energy consumption in buildings
The initial investigations of the performance gap revealed that the usual assumptions, concerning its causes, as it is generally defined during the energy audits in practice, i.e., climate data, internal temperature, and electricity consumption, do not explain the performance gap for this case study, since it concerns an energy-efficient building
The following conclusions could be drawn: (a) Among the reasons explaining the performance gap, we can find the overestimation of the solar and internal gains in the heating demand calculations, errors of the measurement system, wrong configurations of the technical system, the nonrepresentativeness of the normative values included in the simulations, regarding the real conditions of the building or the uncertainty of the parameters controlled by the occupants

Summary

Introduction

The rising of the green building concept has been introduced as a solution to the mitigation of the energy consumption in buildings. It was realized soon that the monitored and the real performance of the building did not correspond to the one calculated during the design phase of the building This difference, commonly known as the ‘performance gap’, has been already addressed by the scientific community and different studies have been conducted, in order to define precisely the performance gap, its magnitude, explain its causes, and propose solutions in order to deal with it, as summarized thoroughly in [1,2,3]. The unpredictability of the user [2,3,4,5,6,7,8,9,10] constitutes one of the most generally accepted reasons explaining the gap [1] This uncertainty derives from the fact that different parameters influence human behavior, such as psychological or sociological [2], which cannot be quantified or incorporated into the building energy modeling. Other reasons, explaining the performance gap can be the discrepancies between the designed and the real construction, due to limited craftsmanship, as summarized in [1,2,3], the inefficient regulation of the technical systems, [3,6], or the inaccuracies of the measurement system, as mentioned by different studies and summarized in [1,3], etc

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