Leaks at Windows and Doors
2011-12-01
Leaks at windows and doors often cause stains, paint blistering, etc. adjacent to or below the affected window or door, but are not always obvious. In some cases a leak is not noticed until damage to an adjacent wall or other structure occurs. Most window and door leaks are due to deteriorated sealants, improper original installation, wind driven rain, or a combination of these. DETERIORATED SEALANTS Window and door leaks are often the result of deteriorated caulking, gaskets, or other sealants used during the manufacture or installation of the window or door. Sealants within the assembly itself are installed during the manufacturing of the window or door. During installation windows or door are also sealed at the interface between the assembly and the wall opening. These sealants commonly deteriorate over time with exposure to UV and ozone, and may shrink and/or turn brittle. This reduces the ability of the sealant to prevent water intrusion. IMPROPER INSTALLATION The proper installation of a window or door is crucial to performance and weather tightness. Window and door manufacturers provide specific recommendations and instructions for installation, and these should be closely followed by the installer. Some of the potential problems include incorrect installation or material with regards to wraps, flashings, fasteners and sealants. Improper installation can be a serious problem that may require the complete removal and replacement of the affected window(s) and/or door(s). WIND DRIVEN RAIN Wind driven rain is another potential cause of leaks at windows and doors. Essentially, there is no requirement that doors and windows resist leaking during high winds and they often leak under lesser wind forces without being structurally damaged. The 2010 Florida Building Code (FBC) is the building code currently in effect. Chapter 17, Structural Tests and Special Inspections, provides performance and construction requirements for exterior doors and windows. The current FBC does not address waterproofing, sealing and flashing systems of exterior doors and windows; however, it does provide the following requirements that are pertinent in regard to doors and windows: 1715.5.2.1: “Exterior windows and glass doors shall be tested by an approved independent testing laboratory, and shall be labeled to indicate compliance with the requirements of one of the following specifications: ANSI/AAMA/NWWDA 101/I.S. 2 or ANSI/AAMA/WDMA/101/I.S. 2/NAFS or AAMA/WDMA/CSA 101/I.S. 2/A440 or TAS 202 (HVHZ shall comply with TAS 202 utilizing ASTM E 1300-98 or ASTM E 1300-04 or Section 2404).” 1715.5.3: “Exterior door assemblies not covered by Section 1715.5.2 or Section 1715.5.3.1 shall be tested for structural integrity in accordance with ASTM E 330, Procedure A, at a load of 1.5 times the required design pressure load. The load shall be sustained for 10 seconds with no permanent deformation of any main frame or panel member in excess of 0.4 percent of its span after the load is removed. The design pressures, as determined from ASCE 7, are permitted to be multiplied by 0.6. High-velocity hurricane zones shall comply with TAS 202. After each specified loading, there shall be no glass breakage, permanent damage to fasteners, hardware parts, or any other damage which causes the door to be inoperable.” Testing Application Standard (TAS) 202 is entitled Criteria for Testing Impact & Non Impact Resistant Building Envelope Components Using Uniform Static Air Pressure. In regards to water infiltration testing, paragraphs 5.2.2.3 and 5.2.6 state, “Deliver and maintain water spray at a minimum rate of 5 gph/sf, applied at a pressure equal to not less than 15% of the design pressure, maintain this pressure and water spray for a period not less than 15 minutes. No water infiltration shall occur.” An important part of the TAS 202 is that the applied pressure during the water test is only 15% of the design pressure. The North American Fenestration Standard, AAMA 101/I.S./NAFS-02, provides the same 15% design pressure requirement as TAS 202 for testing water infiltration for exterior residential glass doors. Therefore, windows and doors are not required to be designed to resist leaking during hurricanes since the water test is conducted at only 15% of the design pressure. CONDENSATION Condensation at window or door glass usually occurs during periods of colder weather. This condition is not a leak, per se. Rather it is due to the relatively warm and moist interior air coming into contact with the cold window or door glass. The water vapor in the interior air condenses onto the cold glass, and sometimes trickles onto the window sill or wall below. This problem is usually more pronounced at single pane glass or in homes with higher interior humidity.