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Cladding and Curtain Wall Construction 465
Neoprene
thermal break
External
core
Insulation
core
Flanged metal
pans pop-riveted
together
Captive
bolt for
fixing
Composite box
panel of two
metal pans with
insulation core
Figure 7.44 Metal box cladding panel.
is unlikely to suffer distortion of the faces of panels due to differential thermal movement.
Where box panels are used as an external cladding, there is a likelihood of the outer lining
suffering surface distortion due to thermal expansion of the outer face of the panel. This
likely distortion may be limited by the use of comparatively small panels and masked by
profiling the outer metal skin. The aluminium strip box panels illustrated in Figure 7.45
are specifically designed for the building.
The ribbed, anodised, aluminium panels are made by vacuum forming. The outer tray
is filled with Phenelux foam, and the inner tray is then fitted and pop-riveted to the outer
tray through a thermal break.
Separate aluminium subframes for each panel are bolted to lugs on the structural frame.
Continuous neoprene gaskets seal the open drained joints between panels, which are
screwed to subframes with stainless steel screws. The horizontally ribbed face of the outer
skin of the box panels serves the purpose of masking any distortion that may occur, provides
some stiffening to the aluminium strip and provides a decorative finish.
Rain screens
The term ‘rain screen’ describes the use of an outer panel as a screen to an inner system of
insulation and lining, so arranged that there is a space between the screen and the outer
lining for ventilation and pressure equalisation. The open joints around the rain screen,