As builders and homeowners, we are interested in how a window or door performs, their longevity and durability, and how easily they install, and of course the cost. Have you ever given thought to how a window or door is tested by the manufacturer?
I recently had the opportunity to tour Andersen Windows and Doors research and development department, a place called the Garofalo Center for Research, Development and Innovation. This is the facility where, in the words of Andersen, they “test to failure”. Stated in another way, they don’t test to see if a product simply passes a required testing standard, Andersen wants to know at what point their products fail.
My tour guide through the facility was Graham Duthie, Graham, a mechanical engineer by trade and is the Technical Leader of Andersen’s Product Life Prediction Team. As we entered the testing area, we walked by Andersen’s wall of patents, of which they own 265 and counting, patent designs that started in the very early 1900’s and continue through this year.
Once in the testing area, the first test we encountered was ASTM-E547, Standard Test Method of Exterior windows, Skylights, Doors, and Curtain Walls by Cyclic Static Air Pressure Differences. A fancy description of spraying water on a window or door while subjecting the unit to varying pressure differences to see if it leaks. The ASTM-E547 is a laboratory test that tests the unit itself for water leakage, not the installation method.
The test consists of securing a window or door on a test rig, which is sealed on the interior side, then subjecting the window or door to the equivalent of 8-inches of rainfall per hour while applying a pressure difference between inside and outside the window or door, the equivalent of a 55 MPH wind gust or about 360 Pascals of pressure. The unit is then observed for water intrusion. If a leak occurs, the source can be confirmed by use of a dye.
There is a similar ASTM test, called ASTM E331 which can also be performed. The major differences between the E547 and E331 is that E331 is a constant pressure differential test whereas the E547 test varies the pressure (simulating wind gusts rather than a steady wind).
Another test I had the opportunity to observe was ASTM E330, Standard Test Method for Structural Performance of Exterior Windows, Doors, Skylights, and Curtain Walls by Uniform Static Air Pressure Differences. This testing standard tests the structural integrity of the entire window or door assembly to resist the effects of a high wind event, without testing for water leakage. This video shows the amount of deflection this test can create in a sliding patio door.
A similar test standard is ASTM E1233, which uses the same testing parameters, but includes cyclic or varying pressure differentials to simulate wind gusts instead of constant wind pressures.
The most impressive test I observed was ASTM E1886 Standard Test Method for Performance of Exterior Windows, Curtain Walls, Doors, and Impact Protective Systems Impacted by Missile(s) and Exposed to Cyclic Pressure Differentials.
(Not often do you hear missile and window testing in the same sentence.) This test shoots a 2×4 (the missile) out of a cannon, impacting the center of the window or doors glass. A second “missile” is shot at the corner of the window or door glass. Once the window is damaged, the unit is taken to the pressure testing rig and subjected to varying pressures (both positive and negative pressures) to simulate gusty winds and pressure differentials that can occur during a storm. The glazing unit needs to remain intact. The unit being tested must survive 9,000 pressure cycles (the glass, though broken, remains in the frame). Graham mentioned that this is the toughest residential ASTM window and door test to pass.
In addition to the listed ASTM testing that is performed, other testing includes cycle testing of operational hardware on windows and doors. These are automated tests that use motors and other mechanical equipment to confirm durability of operating systems (slides, hinges, locking system, etc…). Controls and cycle counting are all automated, allowing round-the-clock testing.
Windows and doors are used in all climate zones with these products needing to work at 120°F to -40°F. They also need to be able to handle the damaging effects of UV radiation. Much of this testing also happens in the Garofalo Center. Accelerated aging can be performed both in the field, and by testing equipment. The use of machines can simulate the long-term effects of sunlight on window and door components in a much shorter time period than field testing.
The facility also has the ability to create temperature differences across a window or door to test the effects of hot summers and cold winters. This testing can also introduce humidity in the mix, such as what might be expected in hot and humid climates.
One of the bigger surprises of my tour was how Andersen tests the effects of transportation and handling of their products. (There are even ASTM testing standards for shipping packages and containers.) For instance, ASTM D999 Standard Test Methods for Vibration Testing of Shipping Containers, basically the test sees what happens to a product if it rides around unsecured in the back of a truck or trailer, vibration testing.
What I learned from the tour (you don’t know what you don’t know)
My career in the construction industry has primarily been in the residential sector, building in a very stable geological location, with small risks of tornados and only the occasional high wind event. Though we do have cold temperatures and snow to deal with. We don’t typically need windows that can withstand hurricane force winds and the risk of flying debris. Because of this, I was not aware of the PG ratings of windows and doors.
PG or performance grade is a certification rating system that has been standardized across the window and door industry. PG is a design rating that takes into account structural loads, water testing, and air infiltration rates among other requirements. In order for a window or door to achieve a specific PG rating, the unit will need to pass several tests for the target PG, these tests include (when applicable):
- Operating Force
- Air Leakage
- Water Penetration Resistance
- Uniform Load Deflection
- Uniform Load Structural Resistance
- Force-Entry Resistance
The PG rating value given to a window or door corresponds with the structural load or design pressure the unit is engineered to handle. For instance, a PG rating of 20 will show a window or door can handle 20 PSF of structural loading. The unit will also have to pass the additional ASTM test requirements. The scale goes as high as PG 100, which is a rating applied to a product that can handle wind loads of 200 mph. Of course, higher PG ratings often result in a more costly window or door, but not always.
I asked Graham during my tour, why do you perform so much testing? I would think that eventually, you would have tested all your window and door lines and would only need to test new products in development. Graham stated that Andersen will retest a product if there is a change in a material supply vendor or material type. Andersen has the ability to model changes in materials and designs using software long before producing a product, but physical testing is used to confirm if the changes performed were correctly.
My tour through the Garofalo Center for Research, Development and Innovation was educational and informative. The amount of research and testing performed in this facility to advance window and door technology is impressive, and I thank Andersen for the opportunity.
This post originally appeared on the Green Building Advisor website.
Very insightful. Thanks.