thermal imagines clearly show that the male–female interlock joints have a lower thermal resistance than the centre of the panel for the samples S5 and S9 and the thermally zones are quite homogeneous, while in the sample S3 the presence of the joints is more evident. The particular shape of the joint and the presence of small cavities assure limited convective motions inside the interspaces of the joint; obviously the thermal transmittance measured in correspondence to the joint is lower than the punctual values obtained for the centre of the panel.