polycarbonate. Because of its softness, the ionomer tends to
grab the blade of a saw and is somewhat self healing when cut.
Insulated/Air Gap Cross-Sections. Insulated or air gap
glazing provides heat transfer benefits. Typically, an air gap
glazing can reduce a temperature gradient by 50 percent. This is
an important consideration for security applications requiring
larger thicknesses of polycarbonate (see paragraph on laminated
polycarbonate) where thermal stresses can significantly reduce
the life of a product. Security applications which require
larger thicknesses of polycarbonate include forced entry
resistant cross-sections requiring longer delay times and blast
overpressure resistant cross-sections where the resistance
function is calculated from polycarbonate material.
Frames. Glazing frames provide a connection or
interface between a building envelope and glazing material. This
connection must be as strong as the other components of the
system to maintain the integrity of the building. For security
glazing systems, frame strength is required to resist attacks as
well as environmental effects.
This paragraph describes frame systems and discusses
design considerations related to attack resistance of frames.
Frame Systems. A basic frame system consists of a main
frame, removable stop, fasteners, glazing tape, setting blocks,
and sealant. More elaborate frame systems include subframes.
This paragraph describes the following components of a frame
Glazing Tape, Sealant, and Setting Blocks
Main Frame. A glazing frame can be made from aluminum,
aluminum with steel inserts, or steel. The frame must provide a
system of drainage channels and flashing as necessary to weep
water to the exterior. Operable frame designs for security
applications are not recommended. Operable designs provide
increased vulnerability to forced entry and blast security
integrity and are costly to produce. Glazing bite should not be
less than a minimum of 1 inch (25 mm) or the minimum determined
by the blast consultant.