The shadow box area is an aesthetic design feature used to mimic the appearance and depth of vision glass areas in order to provide uniform visual continuity across the spandrel areas of a curtain wall elevation. Unlike typical opaque spandrel glass, a shadow box spandrel feature is an area with clear or tinted glass and a cavity with an opaque finished back pan attached to the mullions.
The basic configuration of the shadow box can present many building envelope design challenges. These include:
- Excessive heat buildup within the shadow box cavity
- Glass breakage due to excessive thermal stress
- Glass distortion or delamination (for laminated glass)
- Heat transfer from the mullion to the interior
- Condensation and moisture buildup in the shadow box cavity
- High air pressure in the cavity and structural stress on the back pan and glass
- High temperature and air pressure differentials resulting in seal failure
- Air/water/dust infiltration due to the venting/drainage scheme
The severity of potential heat gain within the shadow box cavity depends on a combination of many project-specific conditions: the shadow box orientation relative to the sun, the local climate, glass makeup VT/SHGC, the albedo of the shadow box finish and the ventilation strategy used on the shadow box cavity.
There are different shadow box cavity ventilation design strategies that can be used: venting to the exterior, venting to the interior, mullion venting, or non-vented (sealed cavity). Each of these strategies has trade-offs, pros and cons which must be carefully weighed by the designer according to the project conditions.
Due to the unique project-specific conditions of shadow box design, Tubelite is not liable for the design, installation, or performance of shadow box features. The design of the shadow box and the determination of the shadow box ventilation strategy is the responsibility of the architect/owner – even if the system is part of a “Delegated Design” project.