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Abstract:Building envelopes can play a crucial role in building improvement efficiency, and the adoption of Phase Change Materials (PCMs), coupled with transparent elements, may: (i) allow a better control of the heat flows from/to the outdoor environment, (ii) increase the exploitation of solar energy at a building scale and (iii) modulate light transmission in order to prevent glare effects. Starting from a literature review, focused on experimental works, this research identifies the main possible integrations of PCMs in transparent/translucent building envelope components (in glazing, in shutters and in multilayer façade system) in order to draw a global picture of the potential and limitations of these technologies. Transparent envelopes with PCMs have been classified from the simplest "zero" technology, which integrates the PCM in a double glass unit (DGU), to more complex solutions-with a different number of glass cavities (triple glazed unit TGU), different positions of the PCM layer (internal/external shutter), and in combination with other materials (TIM, aerogel, prismatic solar reflector, PCM curtain controlled by an electric pump). The results of the analysis have been summarised in a Strengths, Weakness, Opportunities and Threats (SWOT) analysis table to underline the strengths and weaknesses of transparent building envelope components with PCMs, and to indicate opportunities and threats for future research and building applications.

Vertical Greenery Modular Systems (VGMS) are an increasingly widespread building envelope solution aimed at improving the aesthetical quality of both new and existing façades, contemporarily achieving high energy efficiency performance. Within a research project a new prototype of VGMS was developed, designed and tested. An experimental monitoring campaign was carried out on a test cell located in Turin (northern Italy), aimed at assessing both biometric parameters and energy related issues. Two different types of growing media and two plant species, Lonicera nitida L. and Bergenia cordifolia L., have been tested on a south facing lightweight wall. Results have been compared to the same wall without VGMS and plaster finished, in order to characterize the thermal insulation effectiveness in the winter period and the heat gain reduction in the summer period. Measured equivalent thermal transmittance values of the green modular system showed a 40% reduction, when compared to the plastered wall, thus noticeably impacting on the energy crossing the façade during the heating season. Benefits of the VGMS are measured also during the summer season, when the presence of vegetation lowers the outdoor surface temperatures up to 23°C compared to the plastered finishing, with a positive effect on outdoor comfort and urban heat island mitigation. Nevertheless not significant reduction was observed as far as the entering energies are concerned, since the green coverage acts as a thermal buffer and solar radiation is stored and released slowly if compared to the plastered wall.

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