Film Opacification

Under certain lighting conditions it is possible to see through most reflective spandrel glass, even those with less than 10% light transmission and with dark insulation behind. If the thermal insulation does not have an absolutely uniform color or texture, the exterior appearance must be controlled by making the glass opaque. This is normally done by applying a plastic opacifier film directly to the back of the monolithic reflective coated glass spandrel panel by means of a contact adhesive. HGP offers both polyethylene and polyester opacifier films. Polyethylene is most often used. Care must be taken to insure that the backup thermal insulation does not come in contact with, or adhere to, the opacifier film. A minimum air gap of 1/2" should be maintained between the spandrel glass and insulation or other building components to reduce the possibility of the film experiencing excessively high temperatures. The cavity between the glass and the insulation should be vented to permit natural cooling through convection.

When monolithic reflective spandrel glass is used in structural glazing applications, the opacifier film must be cut back, to expose the glass surface along the edges to ensure proper adhesion between the silicone sealant and the glass.

Shadow Box Opacification

In this application a plastic opacifier film is not used; instead, a uniform dark gray or black rigid insulation, protected by a vapor barrier, is used to minimize or hopefully avoid read through from the outside. The insulation is installed 1 to 2 inches behind the inside surface of the monolithic reflective glass. Even when a "perfect" moisture vapor barrier is obtained, moisture can still enter the shadow box air space, so the cavity between the glass and the insulation must be properly vented and weeped to the exterior to deter corrosion or condensation buildup.