Solar Energy

European Directive 2010/31/CE on energy efficiency in the buildings sector provides for significant actions for the reductions in energy consumption, and Directive RES 2009/28/CE stimulates the use of energy from renewable sources in order to meet such objectives. The chapter presents indications about the use of solar radiation for the energy requalification of buildings based on the results of research activities. Simplified evaluation methods are presented with the aim to verify the available potential energy, for the production of sanitary hot water, for winter heating and for the production of electrical energy, by means of systems which use conventional solar collectors placed on the surfaces of the building shell, in particular on the roof slopes. In order to evaluate the energy improvement linked to the solar gain through the windows, the direct gain is evaluated by means of an accurate calculation model of the solar gains, which uses the coefficient of effective absorption of the entering radiation. With regard to sunspaces, some aspects of the thermal analysis, of the evaluation of the solar energy absorbed by the sun space and by the adjacent room and of the benefits obtainable in terms of a reduction in the thermal requirements of the adjacent spaces are discussed. Finally, a discussion is presented regarding the possibility of using phase change materials (PCM) for the refurbishment of lightweight buildings.This technique allows for the improvement of the response of the building to solar gains, thus providing better thermal comfort in summer. In order to facilitate comprehension, the topics are supported by calculation methods and accompanied by numerical examples.