The interplay of building physics and climate : passive design in heritage buildings

Abstract

The use of fossil fuel-based energy in buildings generates greenhouse gas emissions and contributes to a rise in global temperatures. This increases the cooling demand in buildings to achieve a level of indoor thermal comfort. Passive strategies provide a more sustainable means of stabilising the indoor thermal environment as they rely on the physical characteristics of the building while including other non-intrusive strategies. This is particularly critical for heritage buildings, going beyond human comfort, where mechanical systems could have negative impacts on the preservation of sensitive artworks or artefacts. As part of this research, the thermal comfort performance of Sarria Church, Malta was assessed through environmental monitoring, occupant questionnaires and building simulation. Both temperature and humidity were monitored using data loggers, while DesignBuilder simulations examined the effectiveness of different passive strategies, such as natural ventilation, night cooling and roof reflective coatings. Monitoring results indicated that thermal mass played a major role in stabilising indoor conditions, but is not sufficient on its own, especially during warmer months as the mean internal relative humidity exceeded the ideal conservation range of 40-55% in most areas, reaching up to 71% in March. The simulations showed that nighttime cooling through ventilation was essential at reducing internal stagnant air while also reducing peak indoor temperatures by up to 2.1°C when compared to the base case. At the same time, light coloured roof reflective coatings reduced heat gains, further resisting heat ingress through the building envelope of the church. Overall, these results showed that passive design strategies can contribute significantly to reduce cooling demand in heritage buildings while preserving their architectural and historical identity and decorative artefacts.