Synergic effects of thermal mass and natural ventilation on the thermal behaviour of traditional massive buildings

The energy policies about energy efficiency in buildings currently focus on new buildings and on existingbuildings in case of energy retrofit. However, historic and heritage buildings, that are the trademark ofnumerous European cities, should also deserve attention; nevertheless, their energy efficiency is nowadaysnot deeply investigated. In this context, this study evaluates the thermal performance of a traditionalmassive building situated in a Mediterranean city. Dynamic numerical simulations were carried out on ayearly basis through the software DesignBuilder, both in free-running conditions and in the presence ofan air-conditioning (AC) system. The results highlight that the massive envelope of traditional residentialbuildings helps in maintaining small fluctuations of the indoor temperature, thus limiting the need forAC inthe mid-season and in summer. This feature is highly emphasised by exploiting natural ventilation at night,which allows reducing the building energy demand for cooling by about 30%.The research also indicatesthat, for Mediterranean climate, the increase in thermal insulation does not always induce positive effectson the thermal performance in summer, and that it might even produce an increase in the heat loads due tothe transmission through the envelope.