Hurricane and High Wind Zones

In areas prone to hurricanes and high winds, here is a summary of steps that can be taken to improve the storm resistance of exterior doors based on the detailed information provided below and in the cited documents by FEMA and others:

• All exterior doors on homes in hurricane areas should be pressure and impact rated or protected by a system that is pressure and impact rated, according to the Insurance Institute for Business & Home Safety (IBHS 2019).
• Doors should be properly flashed, weather stripped, air sealed, and set in pan flashings designed to resist the entry of wind and wind-driven rain.
• For increased disaster resistance in coastal and high wind areas, install exterior doors to swing outward rather than inward. Weather stripping should be installed on the interior side of the doors to minimize decay.
• Consider designing the home’s entry with a vestibule and outer and inner entry doors. Construct the entry with durable water-resistant flooring.
• Install water-resistant flooring at all entryways.
• Doors, door framing, and door hardware should be made of water-resistant, corrosion-resistant materials.
• Exterior doors should meet U-factor requirements for the home's climate zone, as required by local building codes. Please see the Compliance Tab for more information.
• FEMA P-499 “Technical Fact Sheet No. 6.1: Window and Door Installation,” provides some best-practice approaches that can be taken to reduce water infiltration. Pan Flashing, weather stripping, and threshold seals are discussed. The Solution Center guide Fully Flashed Window and Door Openings and the “Tech Note: Window and Door Flashing: Code Requirements and Best Practices” by Home Innovation Research Labs provide additional detailed instructions for installing window and door flashing.

In all areas where buildings are constructed, windows and doors tend to be more vulnerable to damage than other portions of a building’s envelope. In coastal areas where high winds, windborne debris, and wind-driven rain are common and often intense their vulnerabilities are more pronounced (FEMA P-762 2009). Air leaks around doors can allow in wind during high-wind events, contributing to an increase or decrease in internal pressures that can contribute to building failures (FEMA P-762 2009). Flashing is required by the IRC Section R703.8 to prevent moisture from entering the wall system.

Water leakage around windows and doors is also quite common but because the effects of water leakage are often subtle, the full effects of water leakage are often not readily apparent. Water-resistant siding materials like vinyl and veneer can hide moisture damage in the sheathing caused by rainwater entry for years. Leakage or water entry, due to inadequate or improperly installed flashing, weather stripping, or weather-resistant barriers, can allow water to enter a building’s interior even when the structure of the window or door remains intact. Water intrusion can cause rot and fastener corrosion that can weaken the window or door frame or the wall framing itself. Leakage can also cause damage to interior finishes and facilitate mold growth (FEMA P-762 2009).

Windows and doors can fail if they are not strong enough to resist wind pressures from a high-wind event or if forces exerted on the doors or windows exceed the strength of their anchorage. When strength is inadequate, the window or door’s glazing or frames fail; when anchorage is inadequate, the entire door or window unit can be torn from its mounting. As wind speeds increase due to storm strength in Category 2 or weak Category 3 levels, failures of these elements become more frequent. Wind pressure increases resulting from the failure of windows and doors can significantly increase (in some cases doubling) the wind forces working to blow the roof off or blow out exterior walls.

FEMA P-762 Local Officials Guide to Coastal Construction provides the following guidance on window and door leakage (excerpted). Hurricanes and coastal storms can pose significant problems from water infiltration due to wind-driven rain. Leakage can occur between the door or window and their frames and between the door/window frames and the walls onto which they are mounted. Coastal storms such as tropical storms and hurricanes generate winds that may approach or exceed the wind speeds observed during design wind events. As such, these winds generate high-wind pressures on the outsides of the buildings, exploiting any vulnerability around doors and windows and allowing water to enter buildings. Further, leakage rates typically increase with greater wind speeds. While the amount of  water entry that can result from leakage around windows and doors will typically be much less than the amount of  water entry that can result from a breach in the building envelope, actions can and should be taken to help reduce leakage around doors and windows. These actions are often code-plus or best-practices approaches.

Code Requirements for Window and Door Leakage - Proper door and window construction is critical to reducing water infiltration. Section R613.4 of the IRC and Section 1714.5.1 of the IBC require windows and sliding doors to be certified per AAMA/ WDMA/CSA 101/I.S.2/A440, Standard/Specification for Windows, Doors, and Unit Skylights. Hinge doors must be certified per ASTM E330, Standard Test Method for Structural Performance of Exterior Windows, Doors, Skylights, and Curtain Walls by Uniform Static Air Pressure Difference. Both standards specify wind-pressure and water-leakage criteria that must be met in order to comply with code requirements. In general, water-leakage tests are conducted at much lower differential pressures (typically 20 percent) than the pressures used to determine the strength of the glazing, window, or door assembly. This implies that some water entry through doors and windows should be anticipated during an event that produces design wind pressures and wind-driven rain.

Reducing Window and Door Leakage - FEMA 499, Technical Fact Sheet No. 6.1: Window and Door Installation, Window and Door Installation, provides some best-practices approaches that can be taken to reduce water infiltration. Pan flashing (i.e., flashing under window sills), weather stripping, and threshold seals are discussed. Other actions can be taken to reduce the potential for water entry. These include:

• Vestibules. Designing a vestibule, or double-doored entry, to protect a door entry is one method of managing water infiltration problems. Through this approach, both the inner and outer doors can be equipped with weather stripping, and the vestibule itself can be designed to tolerate water. For example, water-resistant finishes (e.g., concrete or tile) can be specified, and the floor can be equipped with a drain. As a result, a secondary layer of protection is provided for the primary entrance (via the vestibule and vestibule door).
• Door swing. Out-swinging doors offer an advantage compared to in-swinging door assemblies. With out-swinging door assemblies, the weather stripping is located on the interior side of the door, where it is less susceptible to degradation than the exposed weather stripping on in-swinging door assemblies. Also, some interlocking weather-stripping products are available for out-swinging door assemblies that provide better performance than those used on in-swinging door assemblies.
• Finish selection. One design approach to deal with leakage is to avoid running carpet (or other finishes that can be damaged by water) entirely to the edge of walls that contain a large amount of glazing. Instead, a strip of water-resistant material (such as tile) could be specified along the wall so, if leakage occurs, the potential for damage to interior finishes and contents is greatly reduced.

Window and Door Assembly Capacities - Window and door assemblies must be strong enough to withstand wind pressures acting on them and be fastened securely enough to transfer those wind pressures to the adjacent wall. Pressure failures of doors or windows can allow glazing to fracture or glazing frames or supports to fail. Anchorage failures can allow entire door or window units to be ripped from their walls. Either type of failure results in the failure of the building envelope and allows wind and water into the building.

Code Requirements for Strength and Anchorage - Both the IRC and IBC contain specific requirements for the wind resistance of windows and doors. Section R613.3 of the IRC requires that exterior windows and doors be designed to resist the wind pressures specified in Table R301.2(2). Table R301.2(2) lists positive and negative wind pressures for C&C for various locations within the building. Areas near roof and wall edges and areas near corners, where turbulence creates localized high wind pressures, must be designed for higher loads. Table R301.2(2) is based upon Exposure B conditions for buildings with a mean roof height of 30 feet or less. Table R301.2(2) pressures must be multiplied by factors listed in Table R301.2(3) for different mean roof heights and exposures.

The IBC requirements are similar but are less prescriptive and more performance based. While the IRC has tabulated wind pressures, Chapter 16 of the IBC specifies acceptable methods of calculating wind loads and (in Section 1603.1.4) requires that construction documents list wind pressures for C&C.

IBC Section 1405.12, Exterior Windows and Doors, requires windows and doors to be tested in accordance with IBC Section 1714.5, which lists two methods of establishing wind resistance. Section 1714.5.1 allows doors and windows to be labeled per AAMA/WMDA/CSA 101/I.S.2/A440; Section 1714.5.2 allows doors and windows to be tested per ASTM E330. The latter option has additional requirements regarding glass supports and framing that are outlined in Section 2403 and pressure ratings for Section 1714.5.2 are outlined in Chapter 16, the structural design chapter of the IBC.

AAMA/WMDA/CSA 101/I.S.2/A440 lists design test pressures of 15, 25, 30, and 40 psf. Windows and doors used in areas where wind pressures are greater than 40 psf need to be tested per ASTM E330. For residential construction, local officials must ensure that products proposed are adequate to resist the C&C loads of Table R301.2(2). For engineered construction, the designer should specify wind pressures required for windows and doors and should base them on C&C loads from either Chapter 6 of ASCE 7-05 or Chapter 16 of the IBC.

Section R613.8.1 of the IRC requires that windows and glass doors be anchored in accordance with published manufacturer’s recommendations. The manufacturer’s installation instructions should match those used when the units were tested and certified. Substitute anchorage systems are allowed if they provide equal or greater anchoring performance as demonstrated by accepted engineering practice.

IRC contains Figures R613.8(1) through R613.8(8) [Figures R609.7.2(1-8) in 2021 IRC.] that provide minimum anchorage details. The details require windows and doors to be anchored in accordance with the published manufacturer's recommendations. Substitute anchoring systems used for substrates not specified by the fenestration manufacturer shall provide equal or greater anchoring performance as demonstrated by accepted engineering practice. IBC Section 1405.12.1 requires windows and doors to be installed in accordance with approved manufacturer’s instructions.

To minimize issues related to corrosion, the use of fiberglass or vinyl frames are recommended for buildings located within 3,000 feet of an ocean shoreline. The use of stainless-steel frame anchors, fasteners, and hardware is also recommended within these areas.

Pests

Damp wood attracts termites and carpenter ants and makes wood framing and sheathing easier for rodents to gnaw through. Window and door flashings that are properly integrated with the wall weather-resistant barrier will help to keep the wall assemblies drier and discourage pest entry.

In areas where severe termite or insect infestation problems exist (see termite infestation map, Figure 1), wood frames should either be treated or should be constructed with wood that is naturally insect- and rot-resistant. Shims and bucks should be pressure-treated. Since some pressure treatment increases the moisture content of framing, the use of material that is kiln dried after treatment is suggested to control shrinkage.

In areas where insect infestation problems exist, metal door assemblies are recommended. If concrete, masonry, or metal wall construction is used to eliminate termite problems, wood used for blocking or bucks should be treated, or naturally insect- and rot-resistant species of wood should be used (FEMA P-762 2009).