Strengthening the effectiveness of building energy efficiency labels for existing office buildings in Taiwan

To achieve the national goal of net-zero emissions by 2050 and systematically manage the energy efficiency of existing buildings, Taiwan began implementing the Building Energy Label Certification in 2022. This certification grades building energy efficiency by comparing the Energy Use Intensity (EUI) based on energy bills with the EUI benchmark.

However, the EUI benchmark only considers the efficiency of the building envelope, HVAC system, and lighting. It sets a unified standard for commercial office buildings, ignoring the fact that different buildings have varying shape and usage intensities. As a result, most existing office buildings are classified below level 6, which is considered a disadvantageous rating.

This study alternatively proposes using the ASHRAE 90.1 Baseline to establish reasonable EUI benchmarks tailored to the actual conditions of existing buildings to address the current challenges. Firstly, 500 commercial office building models were established using the Monte Carlo method. The EUI distribution probability of these 500 cases, obtained through EnergyPlus simulations, aligns with the EUI distribution probability of existing commercial office buildings published by the Taiwan Energy Bureau.

The comparison with the current single benchmark grading method indicates that using the ASHRAE 90.1 Baseline for grading can resolve the issues of underestimating the energy efficiency levels of buildings with a high perimeter zone ratio or high equipment density, as well as overestimating the energy efficiency levels of buildings with a low perimeter zone ratio or low equipment density.

Additionally, by referring to EN15217 to adjust the grading intervals, the overly stringent current benchmarks and the excessively narrow intervals between levels 1 to 4 can be addressed. This adjustment allows for more effective differentiation of energy efficiency and results in a more reasonable distribution of grades for existing commercial office buildings.

The results indicate that the proposed grading method in this paper can enable policymakers to establish a reasonable and fair energy efficiency rating system for existing commercial office buildings, and potentially extend it to other building categories. This system aims to encourage more existing buildings to voluntarily participate in energy-saving initiatives.