Innovative technologies for transparent building envelopes: experimental assessment of energy and thermal comfort data to facilitate the decision-making process

In the last years, energy use for building heating, cooling, lighting and ventilation still accounts for more than one third of the total, primary energy demand in the industrialized countries. In this context, the Directive 2010/31/EU EPBD recast was developed, with the purpose of reducing the EU energy consumption, improving the exploitation of renewables and reducing the greenhouse gas emission. In this perspective, the building envelope system needs to be improved. A number of innovative technologies have been developed but they need to penetrate the market moving from being prototypes and samples in laboratory to be available and usable technologies. In this work it is presented a research aimed at facilitating the decisions making process during the design phase related to building transparent envelopesIndeed, within the national project called "Bâtiville", a configurator library has been conceived to optimize the choice of envelope components to design new near-zero energy districts. The research started with a state of the art and a market survey of some recent innovative solutions for fenestration. Therefore, some of them have been analysed in-field and in test cells: PCM material to improve the poor thermal inertia of the glass and self-switchable technologies such as thermotropic. Experiments were carried out by means of a test cell located on the roof and exposed to real boundary condition in order to continuously monitor the thermal behaviour of the transparent prototypes during different seasons. Results concerning the thermal and energy performance of the different technologies have been used to implement the library of the design configurator and they are presented in this work. Some criticism is underlined when dealing with highly dynamic transparent technologies, due to the fact that it is not possible to characterize their behaviour with conventional synthetic parameters. This difficulty was met particularly for the glazing with PCM and the thermotropic glazing. A new methodology for the design phase is proposed to simplify and optimize the designers' choice among innovative envelope technologies, besides encourage their spread. The experimental results of innovative transparent glazing are presented and discussed, showing promising performances of the innovative technologies analysed.