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Window testing: Ultimate quality control

A little known but fundamental part of the window, curtainwall and building facade industry is the testing of these products in laboratories and also in the field. The purpose of testing windows, curtainwalls and building facades is to ensure that the products will perform as intended, and if not, to find out why.

Types of window testing

1. Window testing for certification

North American Fenestration Standard is the place to find window test performance criteria for all types of windows, doors and skylights.

This awkwardly named standard, the AAMA/WDMA/CSA 101/I.S.2/A440-11, also called the NAFS is the bible for determining window test performance criteria and is also for doors and skylights at various quality levels. An excerpt version is available online.

These window tests are performed in a laboratory on standard sized window products, usually individually, to allow a product to achieve a certain “class” or performance category. An example of this would be, according to AAMA/WDMA/CSA 101/I.S.2/A440-11, NAFS — North American Fenestration Standard / Specification for windows, doors, and skylights, a window product being certified as a AW-PG40-AP projected window would need to pass an air test at 6.27 psf with an allowable of .10 cfm/sf. then pass a water test for 15 minutes at a test pressure of 8.15 psf, a structural test at 40 psf with maximum deflection of L/175, then pass a whole slew of other tests. When the window product meets all of these test requirements, it can then be labeled as a AW-PG40-AP, which tells the consuming public that such performance has been achieved.
2. Field test of windows and curtainwalls
A specialized spray rack as seen here is often used in window testing and curtainwall testing for water penetration resistance, both in the laboratory and in the field.

A specialized spray rack as seen here is often used to test windows and curtainwalls for water penetration resistance, both in the laboratory and in the field.

On larger projects it can be valuable to perform the same certification test that was passed in the laboratory, in the field where additional factors have affected the window performance such as handling of the product, installation, condition of the surround and condition of the field applied sealants.

In field window tests, usually only air and water tests are performed in the field, but I have seen a structural test on a curtainwall in the field. Some specifications allow lesser performance in the field than in the laboratory. Sometimes field air tests will have the allowable air infiltration 1.5 times the laboratory allowable. Water tests can be discounted in the field by reducing the test pressure, sometimes by a factor of 2/3.

It is important that the architect specify laboratory as well as field window test performance in order to avoid unnecessary conflict at testing time. This will be a sticking point!

Window test in the field to prove the laboratory performance

Window testing performed in the field to prove the window performs as well in the field as it does in the laboratory. Sometimes this is called prove-out testing or simply “window field testing”. Here, a large chamber is built in an under-construction high rise in Chicago to produce a negative pressure on the inside of the window system while simultaneously spraying the outside. Witnesses observe the window testing while standing inside the chamber

3. Diagnostic window testing

This is window testing performed because something has gone wrong, such as window air or water leaks. In many cases the window testing starts with a reasonable variation of the certification test as a starting point, then other methods are employed to isolate individual parts of the window system to determine exact points of entry. Curtainwalls can also be tested using diagnostic methods.

Diagnostic window testing is an art form requiring a highly experienced test technician because creativity must be sometime used to find the leak. Yet the improvised test should be within reasonable constraints so that the diagnostic window test is not unduly in excess of the project performance criteria.

Window testing in Orlando Florida. This home had leaky windows in stucco wall construction followed by a massive mold outbreak

Yours truly performing diagnostic window testing in a high-end residence in Orlando, Fl. This home suffered a serious but unfortunately common Florida double whammy. Not only did the windows leak volumes of water into the stucco wall construction, but then a massive mold outbreak caused the occupants to need to evacuate.

4. Visual mockup of windows and curtainwalls

This type of mockup is often built on site in advance of the actual construction in order to give the architect and other stakeholders a visual representation of how the window, curtainwall or skylight material will look. It can be effectively used as a standard for visual acceptability as the job progresses. One of my clients, an architect with a university client in New York is using a visual mockup to generate student interest and to attract donor contributions.

5. Pre-construction mockup testing of windows and curtainwalls

This is the mother of all testing and my personal favorite because you get the opportunity to build and test an entire section of the building in a lab where the bugs can be worked out without creating a big problem in the field. Pre-construction mockup testing is a mini-version of the actual project. It has all the elements of a full-fledged construction project including separate drawing submission, separate material order, worker mobilization at the lab. It involves actual assembly and installation of windows, curtainwalls, panels, and possibly even stone or masonry to simulate a part of the actual building. Usually there is an elaborate window test procedure that was initially presented by the architect in the bid specifications, along with a definition of the area to be built and tested in the lab.

Window testing laboratory mockup

Window testing of 435 Van Buren, Chicago pre-construction mockup at Quast Testing Lab in Wisconsin included fixed, sliding and projected windows, sliding and swing balcony doors, inside and outside corners, a sill-height transition and slab covers. You will never see this arrangement at the actual project. The pre-construction mockup is a hybrid of many field conditions found separately on the building, assembled together for window testing.

Continue to Part 2:
Preconstruction Mockup Testing: A Guide for Construction Professionals

More about testing of window and curtainwalls

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Reflection pattern at nickel sulfide inclusion
Varying the light in the picture, the light reflection reveals stress waves emanating from the inclusion. The stress is the cause of the glass failure. It developed slowly as the nickel sulfide inclusion grew over time, pressing against the unyielding encasing glass. One researcher estimated that this stress could reach 100,000 pounds per square inch. When the stress exceeded the ability of the glass to contain it, the glass failed catastrophically. Why catastrophically? Because tempered glass, by design, has a permanent internal tug-of- war to the tune of 10,000 pounds per square inch everywhere in the glass plate. Disrupt that structure, and you get...pop!


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