• Energy efficiency
• Energy savings in buildings
• Sustainability
• Post-disaster housing
• Lightweight buildings
• Advanced building envelope systems
• Phase-change materials
• Vacuum insulation panels
• Adaptive façades
• Resilient cooling

Owing to its significant role in the total energy consumed worldwide, the building sector needs continuing the development of new sustainability concepts, technologies and materials. A relevant role in the building life cycle is played by the very beginning phase, which includes the production of materials, the transports and the site operating phase. Accounting the overall energy spent for construction and demolition, its share is increasing up to 50% of the total energy consumption. As a result, over the last few years, alternatives to the traditional heavyweight constructive methods have been emerging and proliferating. A significant example is the development of prefabricated buildings that have been obtaining success for their many advantages in the development of building industrialization: modularity, sustainability, transportability etc. This type of building concept is most frequently related to temporary accommodations. Therefore, the focus object of this research is categorized as prefabricated lightweight temporary building (PLTB). As a common example, PLTBs play a critical role in disaster response and recovery by providing a temporary home for displaced people before they return to their permanent residence.
Although targeting the EPBD goals towards a more sustainable built environment with energy savings during construction phase, PLTBs present some drawbacks regarding consumptions during their useful life. Such building concepts have low effective thermal mass and thus show a fast response to temperature and heat flux excitations, leading to risks for not meeting the occupants’ comfort and HVAC energy-saving requirements throughout the building’s life cycle. The sensitivity to overheating during summer can be partially reduced through increasing insulation on the façades, whose heat exchanges are the major contributor to space cooling loads. On the other hand, when it comes to lightweight buildings, there is a need to guarantee modularity and to conserve the limited internal space, so any intervention made on the building envelope has to be as thin as possible to save space and allow for quick installation
Literature shows a wide range of technologies for building envelopes, among which, only the state-of-the-art solutions with low thickness are selected in the research to preserve the limited available internal space of PLTBs. Thanks to its high insulation performance and its potential in keeping the envelope thin, the unique static intervention analysed in this research is the implementation of vacuum insulation panels (VIP). While, among the most promising and emerging dynamic building envelopes, the author decided to focus on phase-change materials (PCM) for their intrinsic ability to increase thermal heat storage, and switchable coatings, subdivided into thermochromic (TCC) and electrochromic coatings (ECC). These last two interventions, based on switching solar absorptance of opaque surfaces according to external stimuli, are analysed for transparent surfaces too, but by switching solar reflectance of glass. These are called thermochromic (TCW) and electrochromic windows (ECW). The research objective is to compare the effectiveness of the mentioned measures in achieving thermal comfort, especially for summer overheating protection, both in active and in passive ways. An overview of thermal performances is given to understand the relativeness between different ways to prevent the thermal issues of lightweight envelopes. Considerations about changing the flow rates and schedule control of ventilation are also taken into account to better investigate potential thermal improvements. To investigate potential different optimal designs, two different Koppen climate scenarios were taken into account: Amsterdam (with a Oceanic Climate, Cfb) and Florence (with a humid sub-tropical climate, Cfa, trending to the Mediterranean).
Besides the energy performance, the research consider other priority, such as the occupied space in the box, the transport flexibility and the energy independence. For this last factor, a study of the potential PV implementation on the roof of the building is also included as a reference benchmarking information. The main aim is to investigate the potential amount of solar on-site electricity generation and to consider different PV options according to different preferences. Both grid-connected and off-grid scenarios are analysed to evaluate the different decision-making factors in case of energy dependence or independence by the grid, respectively.
Particularly concerning the analysis of switchable solutions, it is found that the impact in both energy efficiency and thermal comfort in free-running mode of a switchable intervention can be higher in the opaque surfaces for warmer climates and higher in transparent surfaces for colder climates. Nevertheless, the most energy efficient measures turn out to be VIP and PCM but with opposite natures: the first one represents a better energy solution for winter while the second one a better thermal comfort solution for summer.
Considering the PLTB manufacturer as the primary decision maker, different priority factors are discussed according to different goals. For example, the high benefit of on-site PV electricity generation and its potential off-grid option are particularly useful for PLTBs in post-disaster and festival events cases. The research illustrates different scenarios to give a support to the manufacturer decision-making process for different target applications.