## 3 Case Studies
### Casa Cembo  
The walls of the Casa Cembo house were made of straw bales placed flat and plastered on both the inside and outside for a total thickness of about 55 cm (48 cm of straw and 3.5 cm per part of plaster).  
The external plaster consists of 3 layers. The first two layers, which were made of lime putty, metakaolin, sand, and straw (albeit more in the first layer), were placed at close intervals. The last layer, which had reduced thickness and consisted of lime putty, sand, and fragments of carbenware or brick (as a hydraulic and coloring agent), was placed after the first two had dried completely.  
With the aim of maintaining the greatest possible material uniformity, the straw bales were inserted into a 180 cm wooden frames. For the same purpose, the pillars, which had a reduced cross-section with respect to the thickness of the wall (22 cm versus 55 cm for the wall), were completely incorporated between the straw fibers, which had filled the spaces in front of the wooden structure during compression.  
The vertical compression of the wall, measuring about 2 cm per row, was exerted on wooden slats by means of 2 or 3 hydraulic jacks every wall and was maintained by constraining the system at three points: in the center, with a polyester textile composite straw; and on the sides, with screws fixed to the uprights (Figures 7 and 8). Finally, the straw bales weighed 17 kg and had a density of about 104 kg/m\({}^{3}\)  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{1}{c}{**Characteristic**} & **Casa Cembo Saluggia (Vercelli)** &
\begin{tabular}{c} **Pre-assembled Prototype in** \\ **Verres (Aosta) [11]** \\ \end{tabular} \\ \hline Altitude & 186 m a.s.l. & 383 m a.s.l. \\ Italian climatic zone (A-F) and heating & E (2557 HDD) & E (2793 HDD) \\ degree days (HDD) at 20 \({}^{\circ}\)C & E (2557 HDD) & E (2793 HDD) \\ Net floor area & 134 m\({}^{2}\) & 20 m\({}^{2}\) \\ Surface-to-volume ratio & 0.70 m\({}^{2}\)/m\({}^{3}\) & 1.32 m\({}^{2}\)/m\({}^{3}\) \\ Structure frame & wood & wood \\  & 3.5 cm of raw soil + & 3 cm OSB + 37 cm of straw + \\ Straw wall & 48 cm of straw + & 3 cm OSB + \\  & 3.5 cm of natural plaster & 0.2 cm of vapor barrier \\ Heating system & 4–4.5 kW wood stove & 0.71 kW electric heater \\ Domestic hot water system & 2 solar collectors & - \\ Photovoltaic system & 4.5 kW polycrystalline modules & - \\ \hline \hline \end{tabular}
\end{table}
Table 2: Main features of the two case studies (OSB = oriented strand board).  
Figure 7: Fixing the bales with a composite polyester textile strap in the center.  
Calcium silicate panels were used for the window edgings to solve the thermal bridging problem related to the wall-window connections and also to characterize the building from an aesthetic point of view (Figures 9 and 10).  
This choice also led to the use of expanding ribbons, with which sealing of the enclosure from air and protection against seepage water were ensured.  
The same attention paid to avoiding water infiltration was also paid to the foundations, where a sort of wooden formwork filled with granular cork keeps the first layer of straw bales away from the ground, including a uniform draining and insulating material support (Figures 11 and 12).  
Figure 8: Compression by means of a hydraulic jack and side fixing with screws.  
Figure 10: Aesthetic effect of the calcium silicate frame.  
Figure 9: Edging of the windows with calcium silicate panels.  
A Foamglass(r) panel on the outside protects the plinth from rain splash-back, and in continuity with the Foamglass(r) laid on the ground, maintains and guarantees thermal insulation and waterproofing of the foundations.