Statistical analysis of energy performance certificates of maltese offices

Abstract

The number of energy performance certificates (EPCs) of offices in Malta represent around 18.60% of the total stock of EPCs for non-dwellings between the period 2010 and 2018, which is significant. Consequently, this dissertation aims to analyse these certificates in order to determine the overall statistical distribution and to identify the worst performing categories, in accordance with the updated EU Energy Performance of Buildings Directive (EU) 2018/844, and to propose pathways to improve their performance through deep renovation to near zero-energy status. Office buildings were categorised into four different groups based on total floor area which is in line with the National Cost Optimal Study of 2018 (≤250, ≤500, ≤1500 and >1500 m²). Results have shown that the primary energy rating and its corresponding Energy Class Rating of these office clusters are different in value, which justifies the categorisation by floor area. Statistical analysis has also revealed that most offices had Energy Class C or D, with the larger offices exhibiting more efficient tendencies (Classes B and C). A number of offices have been considered as outliers because they had EPC rating that were beyond the acceptable limits of statistical tests such as Box and Whiskers Plot, Residual Plots, One-Way ANOVA and Regression Analyses. The study on energy efficiency measures was divided into three main parts, namely the building envelope, the building energy systems and renewables (solar photovoltaics). It was found that the implementation of the optimum building envelope and building energy system measures have yielded an improvement ranging from 28% to 46% for the four office clusters, which is significant and in line with the EU “Energy Efficiency First” Principle, whereby one needs to reduce energy demand before applying renewable energy. With the addition of solar photovoltaics at roof level, all office clusters demonstrated a high potential of achieving a positive renewable energy building, which means that the office becomes a net energy producer. In conclusion, it was recommended that stronger control is needed to ensure quality EPCs. Results that are far from reasonable should clearly be justified or reviewed. Moreover, this study has identified the potential available for the office building sector to contribute towards its decarbonisation with clear and well defined stepped approach, which should help the policy maker to take informed decisions on the deep renovation approaches to be considered for office buildings.

Análisis estadístico de los certificados de eficiencia energética de las oficinas maltesas mediante una metodología propia que consiste en, inicialmente, la creación y depuración de clusters ( en función del área de suelo de la oficina) a partir de un conjunto amplio de observaciones obtenidas de la base de datos de EPC aportada por el Instituto de Energías Renovables de Malta. Seguido del análisis de dichos clusters por separado para obtener oficinas de referencia con las que poder simular medidas energéticas en el software SBEM-mt y de esta forma obtener una vista de la eficiencia energética de estas medidas y su importancia en la mejora de la calificación energética del EPC del edificio simulado.