47.5 MB - The Whole Building Design Guide

3.6.2.2 Windows and SkylightsWindows in older facilities may possess inadequate resistanceto wind pressure. Window failures are typically caused by windbornedebris, however, glazing or window frames may fail as aresult of wind pressure (see Figure 3-110). Failure can be causedby inadequate resistance of the glazing, inadequate anchorageof the glazing to the frame, failure of the frame itself, or inadequateattachment of the frame to the wall. For older windowsthat are too weak to resist the current design pressures, windowassembly replacement is recommended. Some older window assemblieshave sufficient strength to resist the design pressure, butare inadequate to resist wind-driven rain. If the lack of water resistanceis due to worn glazing gaskets or sealants, replacing thegaskets or sealant may be viable. In other situations, replacing theexisting assemblies with new, higher-performance assemblies maybe necessary.Figure 3-110:Wind pressure causedthe window frames onthe upper floor to fail (redarrow). Hurricane Katrina(Mississippi, 2005)It is recommended that all non-impact-resistant, exterior glazinglocated in hurricane-prone regions (with a basic wind speed of100 mph or greater) be replaced with impact-resistant glazingor be protected with shutters, as discussed in Section 3.4.3.2.3-138 MAKING CRITICAL FACILITIES SAFE FROM High Wind