STRUCTURAL GLASS FACADES - USC School of Architecture

of the spacer, and the application of sealant around the entire perimeter. The perimeter seal
is generally comprised of two materials and is called a dual seal; a primary seal of
polyisobutylene and a secondary seal of silicone. Other materials are sometimes used as
the single seal or secondary seal. As the weather seal in most structural glass facades is
provided by a field applied silicone between adjacent glass panels, the silicone material must
adhere to the edges of the glass panels. It is therefore critical that silicone, or a material
compatible with silicone be used as the outer seal on the IG’s.
The aluminum space contains a desiccant material that works to absorb moisture that may
inadvertently enter the cavity. The spacers are typically anodized aluminum, and the
aluminum color of the spacer is visible within the air cavity. Some manufacturers are offering
the spacer in black.
Insulated glass units can be made of varying glass thickness and air cavity depth; the larger
the air cavity the better the thermal performance. Other techniques are also used to improve
thermal behavior. Certain gasses with improved insulation properties over air, such as
argon, can be used to fill the cavity of the IGU. Body-tinted glass can be used, and various
coatings such as low-e discussed below, can be combined in the IGU makeup. Various
products are on the market that make use of the air cavity to improve thermal properties and
light transmittance; infill materials ranging from gels to special miniature Venetian blinds. U-
values (see 2.4.3 below) are improving, and ongoing research and development continues
to be highly productive in improving the thermal performance of glass. Some of these
products are expensive, but as energy costs rise and use of these products increases,
product costs can be expected to drop.
2.4.1.8 Laminated Insulating Glass
Glass panel fabrications can be both insulated and laminated. Insulating laminated glass is
an IG unit in which the exterior component is a monolithic glass ply and the interior
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