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Advertising supplement provided by Pittsburgh Corning

Performance

These unique properties of glass block translate into special performance characteristics regarding fire resistance; resistance to surface condensation, light, heat, thermal and shading performance; sound transmission; and earthquake resistance.

Fire-resistance. Presently, no glass block assemblies qualify as fire-rated wall assemblies. Unlike the wall assembly test that measures a material’s integrity, stability and thermal transmission, the glass block window test only determines the ability of the assembly to remain structurally sound and prevent passage of smoke and other noxious fumes during the fire test. Therefore, all assemblies must meet standards set for windows (ASTM E 163) rather than walls (ASTM E 119).

All UL fire-rated glass block on the market meets a 45-minute or longer duration test. Thicker faced and solid units are available with ratings of 60 minutes and 90 minutes. Basically, the window assembly test consists of exposing a panel to a fire under controlled temperature conditions in a furnace.

The panel is removed from the furnace after 45 (or 60 or 90) minutes and immediately subjected to a standard water hose steam test to determine impact and thermal shock effects. A glass block window assembly passes the hose stream test if at least 70 percent of its glass block do not develop openings through both faces of the block.

For curved construction, 45-minute fire ratings can be obtained provided that the maximum allowable curvature does not exceed a ratio of 2:1 with respect to length of radius to length of assembly width (i.e., chord length), and only installed within masonry fire-rated walls.

Surface condensation. Resistance to surface condensation is considered impressive for hollow glass block because of the double face and partial vacuum construction of hollow glass block. In fact, standard glass blocks are considered condensation-free to minus 15 degrees Fahrenheit and thin blocks to minus 8 degrees Fahrenheit. This compares to a single-glaze flat glass, for which condensation can occur when the exterior temperature reaches 33 degrees Fahrenheit.