Laboratory Assessment and In-Field Monitoring of Macro-Encapsulated Phase Change Materials for Building Envelope Applications  
[PERSON]  
1 CEB Research Group, Department of Energy, Politecnico di Torino, 10129 Torino, Italy;  
[EMAIL_ADDRESS] (G.A. ); [EMAIL_ADDRESS] (E.F.); [EMAIL_ADDRESS] (E.S. );  
[PERSON]SS] (M.P.) [PERSON]  
1 CEB Research Group, Department of Energy, Politecnico di Torino, 10129 Torino, Italy;  
[EMAIL_ADDRESS] (G.A. ); [EMAIL_ADDRESS] (E.F.); [PERSON].S. );  
[PERSON]SS] (M.P.) [PERSON]  
1 CEB Research Group, Department of Energy, Politecnico di Torino, 10129 Torino, Italy;  
[EMAIL_ADDRESS] (G.A. ); [EMAIL_ADDRESS] (E.F.); [PERSON].S. );  
[PERSON]SS] (M.  
winter season, they allow a better exploitation of renewable energy sources (solar energy), because they are able to minimize the mismatch between solar energy production and its usage by shifting and reducing the energy heating demand [4; 5; 6]. PCMs can be incorporated into all the building envelope components: walls, roofs, windows and floors. Four techniques that can be used to incorporate PCMs into building envelopes have been presented in the literature: direct incorporation, impregnation, encapsulation and shape stabilization [7; 8]. In almost all cases, the PCM has to be encapsulated for technical use to avoid problems, such as the leaking of the PCMs and/or the diffusion of liquids through the building materials [1; 9], which can cause surface discoloration and other issues. There are two main ways of encapsulating PCMs:  
* microencapsulation, which consists in packing the PCM materials into capsules which can range in size from less than 1 \(\upmu\)m to around 300 \(\upmu\)m [10];
* macro encapsulation, which involves encapsulating PCMs in any type of container, such as tubes, spheres or panels, capsule stripes, or aluminum profiles, which are usually larger than 1 cm. In the latter case, the containers can be incorporated into building materials or be used as heat exchangers by themselves [1; 9]. A typical solution is that of using metal or plastic film packages, which have become the most established technologies in recent decades for building applications (especially in walls and roofs) and which have a relatively low cost [11; 12; 13]. Several PCM materials have been studied in the last few years, that is salt hydrates (inorganic), paraffin waves (organic), fatty acids and eutectic compounds. Among these materials, salt hydrates are interesting for use in building envelopes because of their lack of or limited risk of catching fire [3; 14], their high volumetric storage capacity, higher thermal conductivity than that of organic PCMs, low volume change on phase transition and lower operating costs than paraffin waves. On the other hand, inorganic PCMs introduce a corrosive behavior to metals, thus leading to a higher cost. [3]  
The application of PCMs to buildings, and especially to roofs, seems to be a promising solution to reduce the energy demands of such buildings and to minimize the thermal discomfort conditions. The roof in low-rise buildings is the largest area exposed to solar radiation, and thus the space below it (the attic) is subject to higher summer heat loads and presents a high risk of overheating [15; 16]. Several studies have investigated the potential of PCMs in building roofs and have highlighted their contribution to building energy saving in different locations. [PERSON] [11] reported the results of some experiments, carried out between 1994 and 2010 in the USA, Brazil and India, on the integration of macro encapsulation PCMs as a part of attic insulation systems. In these tests, it emerged that the major advantage of PCM-enhanced installations is their capacity to significantly reduce and shift the peak thermal loads. In general, the author observed relevant percentage reductions (of up to 44%), in terms of thermal loads and heat flux peaks, compared with a conventional roof without any PCM.