Influence of Thermal Inertia and Solar Radiation on Energy Demand and Comfort: Concept to Retrofit of Italian School Buildings

Most of the Italian school buildings were built before the 1973 energy crisis, so they need a retrofit to reduce energy demand and improve internal environmental conditions. The older buildings have heavy masonry; in these cases, the problem is where it is more convenient to place an additional layer of insulation: inside or outside the building envelope. Moreover, regardless of age, these buildings have large windows; therefore, it is generally necessary to improve the solar control strategy by means of more recent devices. This work is aimed to explore, only by means of computer simulations, the effects of various retrofit strategies on energy efficiency and general comfort conditions. A specific homemade software has been used. Two school buildings of different ages, characterized by different construction technologies, were examined, in a northern Italian climate. In order to assess the influence of internal gains and time profile of use, other possible uses for the same buildings, such as offices or dwellings, have been simulated. The results of simulations indicate that external insulation always performs the best, but in the case of classrooms, the differences from internal insulation are irrelevant. Differences increase with the reduction of the internal gains and with the extension of the period of daily use, therefore with the use as an office and even more with that as a dwelling. Solar control by means of small packable slats inserted between the glasses appears to be the most performing strategy in all cases, both in terms of energy efficiency and visual comfort.