Window frames are such items. They are cooled by contact with the cold concrete panel and in turn cool the edge of the window glass. The centre of the pane of glass may be warmer for various reasons. The higher thermal resistance of a multiple glazed window will keep the inner pane warm; heat supplied by the building heating system can have a similar effect, even with single glazing; and heat-absorbing glass will be warmed by the sun. Thus, a situation is produced in which the edge of the glass is colder than the centre and so is in tension. If the temperature difference is great enough, the glass will break. The cold frame and edge of the glass will, in any case, suffer from condensation.
The connections that hold the panel onto the structure will also be cooled at their outer end by contact with the panel. They, however, must be connected at their inner end to substantial elements of the building structure that provide a means to supply them with heat. Even so, they will be colder than the air inside the building. As there are often passages through which this air can enter the wall, condensation may take place on the connection. Rain leakage through defects in the panel or its joints can also wet the connections. Since the basic layout of the wall is predicated on the idea that the panel system forms a continuous air barrier, it is not possible to introduce outside air to the inside face of the panel to dry the connection. Thus, there is a general increase in the time of wetness, leading to more rapid corrosion.