## 2 Materials and Testing Methods
### Samples Manufacturing and Description  
The feedstock for the panels fabrication was supplied by several companies in Lombardy (Northern Italy) and Sardinia. The cork was obtained from the extraction of the bark of the cork oak, which is processed through a grinding step in order to obtain different size of granules used for the fabrication of cork stoppers. It comes from a historical company from Sardinia (West Italy). Cork is very interesting from a sustainability perspective because it is related to many environmental issues, such as biodiversity conservation and wildfire prevention. The rubber granulate used in this study comes from a big company located in the industrial area of Cherasco (Cuneo, Northern Italy). The company deals with the storage and shredding of the end-of-use tires from a wide area of Northern Italy; the shredding into microgranulates of different diameters (in the 0-4 mm range) allows an easy reuse of the rubber for different purposes: carpets, floors, conveyor belts, and so on. The outputs of the company depend on the final products: rubber chips (30-50 mm), granulate rubber (0.8-20 mm), powder rubber (<0.8 mm). Following the example of other European countries, the company would like to use these residues also as a component for the asphalt pavement. Therefore, the material has already a reuse aimed at respecting and protecting the environment, but it could also be used in the building sector, thanks to its interesting thermal insulation properties. Rice husk is deriving from the paddy rice husking process, the rough rice (unpolished) after threshing. The percentage of rice husk over paddy rice depends on the variety and it can be in the 17% to 23% range by weight. Rice husk contains 75-90% of organic matter, such as cellulose, lignin, and mineral components in different amounts depending on rice variety, soil chemistry, climatic conditions, and even the geographic localization of the cultures [21; 22]. The coffee chaff used in the composition came from an industry of Pavia (Northern Italy); it is the waste of the roasting process of the part that still remains attached to the green coffee beans after the purification and thresh processes [12]. All the tested samples were made in laboratory, in the form of square panels of 300 \(\times\) 300 mm\({}^{2}\) for thermal tests (Figure 1). For the fabrication of these samples, it was used a cold-water-based polyurethane glue, with a density of 1.000 kg/m\({}^{3}\) and a percentage of 2.5% of the total weight. The choice of the weight ratio of the glue derived from many attempts that arose in previous works [12; 16]. It is the minimum percentage able to bind the loose materials and to provide the samples with a good overall consistency. The used polyurethane-based glue was a polyurethane adhesive in aqueous dispersion: this adhesive was found to be easily applied by spray technique and made it possible to achieve the desired results with low doses. The pressing operation was carried out by means of a cold-press system specifically developed for this application: a load of 250-300 kg was applied to each sample and an anti-adhesive spray was previously applied to the surface, in order to simplify the removal of the sample from the formwork. Finally, two support panels of plasterboard (each 6 mm-thick), one for each side of the recycled waste material, were used in order to have self-bearing specimens during the thermal measurements. Their total thicknesses vary in the 51 to 55 mm range, considering the contribution of plasterboard panels; a mean value was considered for each sample (see Figure 1d). The main features of the loose materials are reported in Table 1. Starting from the results obtained in the first survey campaigns [12; 16], it was possible to find the new compositions of the panels. The granulated cork is the material with the best conductivity properties, so that its weight ratio was fixed always higher than the other three.