A client recently sent me an email asking how brand new windows could fail a water test. That’s a good question. The answer deals with two basic considerations:
- Choice of window
- Installation of window
The window and the installation together form an assembly, or system.
1. Choice of window
Clients often choose new windows on the basis of appearance, but the actual performance of a window is more than skin deep. Manufacturers have spent decades and fortunes developing better performing windows.
How can a building owner determine that a window is not going to leak given the particulars of the use and the site? Windows are manufactured to resist a variety of exposure factors and are rated accordingly. Thus, windows should be chosen based upon calculated wind loads, along with other factors.
American Architectural Manufacturers Association (AAMA) is a national trade group comprised of window manufacturers. Building codes refer to AAMA regarding window performance requirements.
To obtain certification for their windows, manufacturers must submit each type of window to a series of tests conducted by an independent laboratory. Such lab testing, repeated every four years in order to maintain the AAMA rating, is expensive and only a handful of labs across the US are equipped with the necessary facilities. Testing includes resistance to water penetration. Consumers may notice an AAMA rating cortication sticker axed to each window frame.
Window manufacturers make every conceivable window type, style and performance class. There are however, many manufacturers that do not subject their windows to independent testing — perhaps due to the cost, or concern regarding performance. I recently led tested windows that leaked at the industry minimum standard. When I inquired about the windows’ rating, the manufacturer answered, “Oh, these are not windows, these are art.”
AAMA has established aggressive testing standards. In part, this helps maintain credibility and the public trust. The objective is to keep the playing field level and weed-out underperforming windows.
Even with the lab testing every four years, window manufacturing changes and leaks occur. As a note of interest, not all windows pass the lab testing, but only successful windows are certified. This helps to explain why field testing may obtain different results and is an important safeguard.
AAMA species American Society of Testing Materials (ASTM) E1105 as the “Standard Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, and Curtain Walls.” This test simulates a wind-driven rain storm. The minimum standard for resistance to water penetration is approximately 3 psf; equivalent to 34 mph wind velocity. Windows are available with higher water resistance ratings; to 60 mph and higher.
Aquatech frequently conducts window water testing to determine if the specimen meets the manufacturers published rating. Typically, the testing is done on newly installed windows up to 6 months old so that failures may be repaired/replaced by the manufacturer before the project is completed. Older windows are tested similarly to recreate and evaluate reported leaks.
Field testing is conducted at 2/3 the AAMA performance grade rating furnished for each specified window, unless specified or agreed otherwise. This pressurized method of water testing with calibrated equipment has been in use for several decades. Simply stated, the windows should pass the manufacturer’s advertised rating. Therefore, the choice of window should comply with the calculated wind loads, plus a factor of 50% since the window performance in the field is down-rated by 1/3.
A wide array of materials are used in the construction of windows; wood, metal, and plastics in many combinations and configurations. Thus, the manufacturing process varies greatly.
No window type is immune to failure. Aluminum frame windows are often assembled with screws and sealant which makes them vulnerable to errors during assembly and leaks may result. Often, large windows are site assembled, so skill, experience and the ability to faithfully execute instructions factor heavily. Vinyl windows are heat welded by robotic process, rendering them less likely to fail. However, windows of all types may suffer from design problems.
What constitutes a leak?
There is some controversy over what constitutes a leak. AAMA offers some guidance. Essentially, a leak is water where it’s not supposed to be. For example, water that pools on a metal part of a window is not a leak, but the same condition on a wood window may be. Water that contacts surfaces other than the window frame is considered a leak.
A word regarding window warranties:
Typically, a comprehensive and extensive warranty comes with the purchase of a window. Most manufacturers are extremely responsive regarding problems. Most manufacturers still accept responsibility, even many years after the initial installation. Long standing national manufacturers often have dedicated repair departments with more resources to mobilize than do smaller companies.
A significant number of reported window leaks are actually the result of installation errors and window manufacturers are decidedly wary. Aquatech is often utilized to determine and report the problems, providing the manufacturer with objective technical information needed for a response.
2. Installation of window system
It would be great if there was one installation that would work for every type of window and for every situation, but in practice, there is not. We design the installation appropriate to each condition. Many installations are straightforward while others require innovative solutions. The starting place is with the window manufacturer. Their installation recommendations should be followed. If there are special considerations the manufacturer should be contacted.
When manufacturer installation instructions are not available, AAMA publishes minimum recommendations. A defining line may be drawn between whether the system is sealed, or whether the system should be drainable. For example, while a manufacturer may not require a drainable sill pan such a system is generally more reliable.
Field testing per ASTM E1105 often demonstrates leaks due to improper installations.
Regarding the number of windows that should be field tested, the window manufacturers have responded recommending more testing. A decade ago 1% was thought prudent. Today, AAMA’s minimum recommendation is to field test 3 of 50 (6%) of each window or door type. This is a voluntary recommendation, so actual testing varies significantly. For example, on new home construction, a homeowner or architect may request testing in order to feel confident in their selections, where testing one of each type may be prudent. A commercial building may have fewer types but more testing. The industry also recommends the number of units tested should conform to a statistically valid sampling. Therefore, half or more windows may be tested in the process of a legal dispute.
In addition to pass/ fail, consideration should be given to evaluating test failures and developing solutions. Following repairs, retesting can confirm if the repairs are satisfactory.
The mantra within the building envelope industry is: “There are only two kinds of windows; those that leak now, and those that leak later.”
The reality is windows and installations are getting better. Still, the failure rate is significant, particularly when testing first installations.
After the initial tests and leaks are resolved, periodic assurance testing during construction is recommended. Errors often occur when there is a change in personnel or crews. In anticipation, Aquatech prepares clear installation protocols to assure fidelity. Window testing follows a standardized protocol so that other specialists may duplicate the procedure and obtain similar results.
While windows and installations may pass the testing, the objective is to gain confidence in the system and to identify problems early in the process of construction.
Additional testing or job-site conditions may result in leaks that the factory or laboratory testing did not produce. Conversely, not testing can prove to be a very costly prospect.
As specialists in preventing water intrusion, Aquatech consultants assist in the process of window selection appropriate to the site conditions, recommend reliable installation procedures, offer assurance and performance testing of installed windows, and provide forensic evaluation of failures.