Demystifying window and door selection for single-family homes in high-wind environments

The failure of the building envelope, including windows, doors and roof coverings, leads to a major portion of the damage of single-family homes wrought by hurricanes. Failure of the building envelope allows wind and water intrusion into the building, and pressurization or depressurization of the interior of a structure may significantly increase differential pressure loads on the structure itself. Damage to windows and doors can result from impact by wind-borne missiles or from the pressure capacity of the unit being exceeded. Commonly available window units may be performance rated (including consideration of air and water intrusion at modest pressures, as well as maximum allowable differential pressure), but there is no readily available means for a house designer, contractor or owner to determine the appropriate rating for a desired window installation (wind-speed claims, while being the simplest to use, are probably the least definable and are the most subject to abuse). Under current design algorithms, the design pressure on windows and doors requires an analysis of each unit based on the dimensions of the unit, the dimensions of the structure, the location of the unit within the structure, and assumptions concerning internal pressurization. This paper reports a design rationale developed under the Blue Sky program for the required pressure capacity of windows that proposes both a window selection tool and a design guide for reducing window pressures (the information is also useful for shutter design and/or selection). The calculated design pressures suggest that most of the windows installed (and being installed) in the 110 mph (fastest mile) zone probably are not rated for the design pressure.