Performance of Passive Solar Systems in Retrofitted Buildings

Passive solar systems can be an efficient strategy to save energy both in new and retrofitted buildings, above all in the Mediterranean climatic zone. Over the last decades many passive solar applications have, indeed, taken place in this area. Contrariwise, there are still few data about the actual performances of passive solar systems; scientific literature shows that studies are limited and often they refer to very peculiar climatic conditions. That happens, basically, because passive solar systems are components of the building envelope, therefore they are dependant on specific environment, operating conditions and budget, hardly replicable and difficult to standardize; so that their performances are hard to evaluate. However, in spite of difficulties to obtain fair operational data it may be useful, for whoever intends to adopt passive solar strategies, to acquire data about their potential performances. This article describes the monitoring actions conducted on passive solar systems, in particular on glasshouses and Trombe-Michel walls, applied in three retrofitted buildings, built in the sixties in Savona (Italy). The winter monitoring campaign has been carried out using temperature data loggers, a thermal imaging camera and an anemometer to measure low air velocities. Those monitoring actions are producing significant data concerning: the operation/efficiency of the checked systems, their performances according to solar radiation absorption, the mode/efficiency of heat transfer, the effect of the users’ behaviour, the validation of information in the literature. The case-studies show that passive solar systems can ensure the necessary thermal transfer and a good indoor comfort in the Mediterranean climate, during not too harsh winters, on condition that the buildings are adequately insulated. Moreover the study remarks on the operating conditions of passive solar systems in relation to the convective heat transfer and the appropriate size of the wall valves as well. The article also shows some precautions to avoid passive solar buildings’ overheating during summer and the monitoring campaign demonstrates that it is easily possible to avoid this problem. The research outputs may be significant in the design and research fields, particularly in order to build up databases able to lead to more reliable simulation systems.