Retrofitting a Mediterranean dwelling into a thermally comfortable minimum energy home : a case study in Malta

Abstract

The motivation behind building dwellings is to provide a secure shelter, protect ourselves from adverse climatic conditions and to obtain a neutral thermal comfort level. The present local built environment has a common thermal comfort problem as most dwellings lack passive measures and thus have a great reliance on electric means that come at a cost to both the individual and the government. In addition such poor thermal comfort conditions imply health problems, leading to another problem - an escalating national health bill. What is certain is that comfort, up to now, has come at a price - a high energy consumption because existing buildings are very inefficient energy wise and consume the largest part of the national energy load. Such a situation, if unchanged, will continue to increase the evident problem of greenhouse gas emissions and the fossil energy demand problem. The main objective of this project was to offer a practical and cost effective working solution to this problem. The feasible energy-saving measures that can be actually retrofitted to an existing dwelling were designed based on previous local and foreign studies and were pointed out accordingly. Such energy-saving retrofit measures were also based on our climatic conditions and existing building fabric to effectively reduce energy consumption. An existing building; a top third floor flat in Birkirkara, referred to as the subject flat, was used as a test bench for such retrofit conversions and was thus converted into a thermally comfortable minimum energy home. The indoor climate of the subject flat, its mirror image apartment and the B'Kara microclimate were monitored for one year and the necessary tools to analyse this data were utilised: a psychrometric chart analysis with locally def Compared to its microclimate and the mirror apartment, the results show that the subject flat (when combined with passive measures - natural ventilation in summer and solar gains in winter) managed to keep quite a constant and very comfortable indoor climate across both the hot and cold seasons. In fact it is only for a small portion (a total of 9 out of 122 days - 7% in summer and 16 out of 121 days - 13% in winter) that the energy-saving retrofit measures failed to satisfy the thermal comfort zones limits. The analysis of such results show that energy efficient dwellings are indeed a possibility in our local climate if retrofitted with such measures. However the analysis also shows that if such a dwelling is left unattended or wrongly used, the tendency is that it will follow the mean outdoor temperature. This case study shows that after 15 years the combined energy saving retrofit measures pay off with a surplus of € 730.29. Considering the thermal comfort status achieved and the energy-cost analysis, stating that such energy saving retrofit measures are not feasible, as most people think, is simply not correct. In fact this project was very successful in its initial objective and its results can be used to aid policy direction and incentives regarding 20-20-20 targets for energy efficiency and reduction.