It is possible to devise suitable joints for these locations, although there are special difficulties mainly related to the thermal conditions to which the panel is subjected. As it is insulated on the inside, a panel will be colder in winter and warmer in summer than would be the case if it were not insulated. As this leads to increased expansion and contraction, the sealant materials or gaskets are subjected to greater strains. Alternatively, the joint width must be increased to allow for the deformation while keeping the strain constant. With a wider joint more sealant is required, there is a greater risk of the sealant's sagging, and, in some cases, it is not acceptable aesthetically. Furthermore, the final portion of the extension takes place when the temperatures are lowest and the sealant or gasket is coldest, and so, stiffest. Thus it can be seen that although joints can be devised to meet the principles set out in CBD 40, there may be some question as to whether, as the sealant materials deteriorate with the passage of time, they will retain their ability to control both rain and air leakage.
The foregoing discussion presupposes that the panel is not cracked. If it is cracked, the situation can be changed considerably. Some hairline cracking of concrete panels is not uncommon and such cracks are usually accepted provided they do not exceed 0.005 in. in width on the exterior face or 0.01 in. on the interior face. The large movement of panels under temperature variations must be allowed for by the way in which they are fastened to the structural frame. If this is not done satisfactorily then the cracks could open further or additional ones be induced. Once there is a crack through a panel, capillarity, gravity, or air pressure can move water into the wall and the principal defence against rain penetration has been breached.