47.5 MB - The Whole Building Design Guide

Figure 3-77:Equipment screen panels,such as these blown awayat a hospital, can breakglazing, puncture roofmembranes, and causeinjury. Hurricane Ivan(Florida, 2004)Water InfiltrationDuring high winds, wind-driven rain can be driven through airintakes and exhausts unless special measures are taken. Louversshould be designed and constructed to prevent leakage betweenthe louver and wall. The louver itself should be designed to avoidwater being driven past the louver. However, it is difficult to preventinfiltration during very high winds. Designing sumps withdrains that will intercept water driving past louvers or air intakesshould be considered. ASHRAE 62.1 (2004) provides some informationon rain and snow intrusion. The Standard 62.1 User’sManual provides additional information, including examples andillustrations of various designs.3.3.4.2 Exterior-Mounted Electrical andCommunications EquipmentDamage to exterior-mounted electrical equipment is infrequent,mostly because of its small size (e.g., disconnect switches). Exceptionsinclude communication towers, surveillance cameras,electrical service masts, satellite dishes, and lightning protectionsystems. The damage is typically caused by inadequate mountingas a result of failure to perform wind load calculations and anchoragedesign. Damage is also sometimes caused by corrosion(see Figure 3-78 and the text box on corrosion in Section 3.3.4.1).3-90 MAKING CRITICAL FACILITIES SAFE FROM High Wind