C. Carletti

Transparent Building Envelope: Windows and Shading Devices Typologies for Energy Efficiency Refurbishments

Main typologies of windows, typical of the existing buildings, and innovative solutions, special glasses, and shading devices (fixed shading, mobile shading, roller blinds, and curtains) are described and assessed. The windows and solar shadings’ appropriate choices are evaluated on the basis of a case study. For each of these solutions, thermal efficiency, natural lighting, and acoustic performances have been assessed with appropriate calculation codes. Dynamic computational methods with a graphical interface are used (EnergyPlus, through the Design Builder interface, for energy simulations, RELUX to simulate natural lighting, and DISIA for the acoustic simulations). Four representative climatic datasets corresponding to various locations (Berlin, Milan, Florence, and Athens) were considered. Appropriate performance indicators (defined by regulations or conventionally applied in science) have been identified in order to analyze performances and to evaluate different strategies for the achievements of energy efficiency and of comfortable environments: Q sw (winter solar gains), θo (operative temperature), F w (reduction factor of winter solar gains), DF (average daylight factor), UDI (useful daylight illuminance), daylight uniformity, D 2m, nTw (acoustic insulation of facade normalized with respect to the reverberation time), and Δl fs (sound pressure level difference due the facade shape). Starting from the performance evaluation of existing buildings, according to a logic implementation of consequential performance, this study provides for the assessment of different phases: the first interventions (phase A), replacement of existing windows with other high-energy performance ones (phase B), adaptation of the thermal transmittance of opaque envelope to national limits (phase C), and introduction to solar systems and solar control glasses (phase D). Then, the effect of screens and windows on the reduction in the thermal loads in the summer season and on the thermal comfort has been assessed, together with the influence on visual and acoustic comfort of different configurations of windows and shielding. Finally, a comprehensive evaluation on the aspects of energy consumption, natural lighting, acoustic comfort, and technical feasibility (TF) is carried out.