Door Installation Guidelines are Latest in Progression of Techniques to Counter Extreme Weather Conditions
August 30, 2011Over the past decade, two emerging priorities have driven much of the research and standards development activity in the fenestration industry: 1) hurricane protection and 2) the philosophy of looking at a wall as a total system rather than a collection of independent components.
The first priority in the wake of the devastating 2004 and 2005 hurricane seasons along the U.S. Gulf and Atlantic Coasts was to upgrade construction requirements to prevent damage from excessive winds and the impact of wind-borne debris. Stronger code requirements for impact-resistant windows have since been adopted in many jurisdictions, ranging from those that reference ASTM standards E1886 and E1996 and/or AAMA 506-11, Voluntary Specifications for Impact and Cycle Testing of Fenestration Products up to those in defined High Velocity Hurricane Zones (HVHZ) – mainly the stringent Miami-Dade standards TAS-201, TAS-202 and TAS-203.
The next level of improvement has focused on reducing water penetration. Through or around otherwise intact openings from wind-driven rain, water penetration can do a significant amount of physical damage, cause occupant displacement and business interruptions and lead to extensive restoration expenses. It can also increase the presence of mold in unseen wall cavities and in spaces between exterior sheathing and cladding.
This issue came to the forefront in 2004 when the Florida Building Commission sought out AAMA’s Southeast Region membership to assess current test methods and develop a standard for testing windows’ ability to resist water penetration under hurricane conditions. AAMA conducted an extensive review and evaluation of existing test protocols and their ability to address the cyclical nature of indoor-outdoor pressure differentials and turbulent flow characteristics of real-world hurricane winds. The effort culminated in the development of AAMA 520-09, Voluntary Specification for Rating the Severe Wind-Driven Rain Resistance of Windows, Doors and Unit Skylights, which provides an optional rating scheme for the ability of fenestration products (windows, doors and unit skylights) to resist severe wind-driven rain, based on ASTM E2268-04.
Proper Installation
But these standards and tests do not account for the performance of the window after installation. Even the best-designed product can fail to prevent excessive water penetration if improperly installed. Despite its importance, installation quality is inherently variable, depending on the experience and expertise of the installer. Codes only go so far as to require that installers follow the manufacturers’ instructions, which can vary in their attention to detail and clarity.
The importance of installation has of course been recognized for some time. AAMA developed the InstallationMasters™ window installer training and accreditation program in 2000, based on ASTM E2112, Standard Practice for Installation of Exterior Windows, Doors and Skylights. In 2002, AAMA also developed the standard AAMA 2400-10, Standard Practice for Installation of Windows with a Mounting Flange in Stud Frame Construction. This standard sought to address the common configuration of windows with integral mounting flanges or fins, emphasizing techniques for fully sealing the window in new construction of detached one- and two-family dwellings and townhouses. Also an extension of ASTM E2112, it includes details of anchorage, use of both mechanically attached and self-adhering flashing and proper sealing.
Additionally, AAMA offers IPCB-08, AAMA Standard Practice for Installation of Windows and Doors in Commercial Buildings. Also based on ASTM E2112, IPCB-08 addresses the installation of windows and exterior hinged and sliding glass doors) installed as part of both new construction or retrofit projects in commercial buildings and replacement projects.
In 2003, AAMA 2410-03, Standard Practice for Installation of Windows with an Exterior Flush Fin over an Existing Window Frame, followed as a companion document to address replacement window installation in which the mounting fin of the new window covers the exterior of the pre-existing window’s frame.
But these guidelines and training programs did not address installations that could better meet the challenge of severe weather conditions. Water penetration resistance test methods as used for certification to the North American Fenestration Standard/Specification (NAFS – a.k.a. AAMA/WDMA/CSA 101/I.S.2/A440 – ASTM E331, E547, etc) evaluate fenestration products in isolation and not as a component integrated into a wall system. Thus the efficacy of the various window or door installation techniques employed in the field was not well understood, and less was known about the leakage paths that can develop. Moreover, it has been unclear how effective these water penetration control strategies work in the extreme buffeting loads associated with the turbulent wind action in a surface layer hurricane wind field.
It soon became obvious that developers, contractors and suppliers needed to address the building envelope as a total system. Given the legal liability that can potentially spread among all players, they recognized that it is naïve to think that each can continue handling its part and merely hope that the resulting collection of products works together properly. Complete and effective system integration is the ultimate solution.
Installation Methods
More to the point, water penetration performance of fenestration products is highly dependent on the moisture control strategy used to integrate the window into the water-shedding surface of the surrounding building envelope. Window and door installation methods to accomplish this integration can be divided into two approaches based on different configurations for the drainage plane (the unrestricted path that incident water follows as it drains from roof to ground).
The first is the surface barrier method, in which the exterior cladding itself is intended to serve as the drainage plane. This approach establishes an air/water seal around the exterior perimeter of the window or door. It is often inadequate to maintain a continuous water barrier over the entire building envelope in climates with frequent and/or heavy rainfall. In addition, once water breaches the barrier and is absorbed by the construction material, the barrier inhibits the ability for the wall to dry out rapidly.
The second approach is the membrane/drainage method, which places the water shedding barrier inside the surface cladding to redirect any leakage to the drainage plane of the wall. The drainage plane consists of a weather resistant barrier (WRB) – traditionally composed of tar paper, polyethylene house wrap, etc. – installed behind the façade cladding and coupled with flashing at the base of each wall. The WRB provides a path for incidental rainwater that penetrates the cladding via superficial cracks, either in the cladding, joinery or installation joints around the perimeter of the window or door, to move down and away from the building. Some form of air space between the cladding system and the drainage plane is essential to allow this drainage to take place, such as by attaching siding to furring strips rather than directly to the WRB-covered sheathing. If this drainage space is not provided, water can be held against the sheathing and may promote rotting, insect infestation, mildew and mold.
In either case, the essential principle of window or door installation is that the unit must work together with the exterior facing material, sheathing and the WRB to form a fully integrated and effective drainage plane. The proper use of flashing and sealants plays a key role in achieving this objective.
The ultimate solution for hurricane water penetration was thus seen to lay in a robust integration of the window or door with the drainage plane.
Installation Practices
In response to the Florida Building Commission’s 2004 request that installation practices be developed for windows and doors in order to address chronic water intrusion issues, the Fenestration Manufacturers Association (FMA) of Tallahassee, FL, formed the FMA Installation Committee to develop installation standard practices. FMA joined forces with AAMA and WDMA to develop robust guidelines that not only specify enhanced water management principles, but do so for the specific wall types found in the coastal southeast region, such as the surface barrier concrete masonry unit (CMU) block wall. The result, unfolding over the past two years, has been the development of a suite of four installation guidelines that address window and door installation in the two different drainage plane configurations and for extreme weather exposure.
Representative installations based on these four methods have been validated through testing for water penetration using the ASTM E331 or ASTM E547 method at a 12 psf pressure (equivalent to the force generated by a 68 mph wind) to simulate exposure to extreme conditions.
FMA/AAMA 100 and 200
FMA/AAMA 100-07, Standard Practice for the Installation of Windows with Flanges or Mounting Fins in Wood Frame Construction specifically addresses new construction of no more than three stories in height utilizing a membrane/drainage system. It goes beyond normal installation practices by specifically addressing installations subject to hurricane-force wind and water exposure. This standard has the option to use 4-inch wide self-adhering flashing or 9-inch wide mechanically attached flashing at the exterior jambs and head.
FMA/AAMA 200-09, Standard Practice for the Installation of Windows with Frontal Flanges for Surface Barrier Masonry Construction for Extreme Wind/Water Conditions, along with FMA/WDMA 250, Standard Practice for the Installation of Windows with non-Frontal Flanges in the same wall system, focuses on the installation of frontal-flanged windows into masonry or concrete (CMU) buildings with surface barrier (e.g., direct-applied stucco) wall construction. In this system, the mounting flange is used to cover a previously-installed mounting buck (a framework built into a window opening in a concrete or masonry wall to which the window frame is secured) and/or to integrate with a pre-cast sill.
FMA/AAMA 200-09 is the first standard ever published to address the unique surface barrier masonry wall construction, commonly found in the southeastern U.S. A key feature of this standard practice is the specification of a water resistant coating (or “Liquid Applied Flashing”) applied around the rough opening return and entire sill area. This treatment is designed to prevent water that either collects or is absorbed into the wall from entering the building interior through the window opening, making the erroneous ”appearance” of a leak at the window or window/wall interface. This water will be directed away from the window/wall interface to exit at the bottom of the CMU wall or other flashing termination.
FMA/AAMA/WDMA 300 and 400
The remaining and most recent guidelines in the suite of four standards offer similar and complementary installation methods for exterior side-hinged or sliding glass doors.
FMA/AAMA/WDMA 300-XX, Standard Practice for the Installation of Exterior Doors in Wood Frame Construction for Extreme Wind / Water Exposure, still in draft stage,is comparable to FMA/AAMA 100 for use with a membrane drainage system, except that it deals with doors. It addresses three scenarios for integrating doors with the membrane drainage plane: doors with mounting flanges, doors with exterior casing/brick molding and non-flanged box frame units. The standard is also designed to align with AAMA 2400-10.
The document covers installation of side-hinged or sliding doors in new CMU construction. To verify the effectiveness of the installation methodology, a mock-up testing program was recently completed to validate the guidelines per the same criteria as the other three guidelines in the suite.
FMA/AAMA/WDMA 400 is expected to achieve final approval via balloting to all three associations in the last quarter of 2011.
All four standards are intended to be extensions of ASTM E2112, Standard Practice for Installation of Exterior Windows, Doors and Skylights per the intent of the ASTM committee, which plans to incorporate such “sister” documents as a means to better focus on specific window/door and wall systems.
It is likely that new and better approaches and upgrades will develop as the level of understanding and technology advances and that all stakeholders can be better assured that window and door installations will live up to the performance promises of the units themselves.
At the AAMA National Summer Conference held in Minneapolis, MN, several Door Council task groups and committees held meetings. These members reviewed documents and discussed other Council activities in order to continue the development and ballot review processes, as summarized below. For more information on the Door Council’s activities, please visit www.aamanet.org/door. in commercial buildings and replacement projects.
American Architectural