Curtain Wall Test Standards, What are curtain wall test standards
Curtain wall test standards speaks to what are curtain wall test standards and why curtain wall test standards for structural performance and resistance to wind and rain. For any new curtain wall design, it is advisable to build and tests a full scale section of wall to determine its resistance to infiltration of air and water and its structural performance under heavy wind loadings.
There are several outdoor laboratories in North America that are equipped to conduct these tests. A full scale specimen of the wall system, often two stories high and a bay wide, is constructed as the exterior wall of a chamber that can be pressurized or evacuated by a calibrated blower system.
Curtain wall testing is conducted according to the American Architectural Manufacturers Association standard AAMA 501 Methods of Tests for Exterior Walls, which itself references numerous standards for specific aspects of the testing.
The specimen is tested first for air infiltration, using ASTM E283 in which it is subjected to a static air pressure that corresponds to the pressure that will be created by the anticipated maximum wind velocity in the vicinity of the building. Air that leaks through the wall is carefully measured, and the rate of leakage is compared to specified standards.
A static test for water penetration is next, using ASTM E331. The wall is subjected to a static air pressure while being wetted uniformly across its surface at a rate of 5 gallons per hour per square foot (3.4 L/ sq m per minute). Points of water leakage are noted, and leaking water is carefully collected and measured. A dynamic water penetration test may also be performed in accordance with AAMA 501.1 using an aircraft engine and propeller to drive water against the wall.
The structural performance of the wall is tested according to ASTM E330, in which a calibrated blower subjects the wall specimen to air pressures and suctions as high as 50 percent over the specified wind load, and the deflections of the structural members in the wall are measured. Optionally, tests for thermal performance, sound transmission and the effects of thermal cycling, seismic loads and movement of the structure to which the curtain wall is attached may also be performed.
While all these curtain wall test standards tests yield numerical results, it is also important that the behaviour of the specimen be observed closely during each test so that specific problems with the design, materials, detailing and installation can be identified and corrected. Most wall system specimens fail one or more of the tests for air and water leakage on the first attempt.
By observing the sources of leakage during the test, it usually possible to modify the flashings, sealants, weep holes or other components of the design so that the modified specimen will pass the subsequent test. These modifications are then incorporated into the final details for the actual building.
After testing has been completed and final design and adjustments have been made, production of the wall components begins and deliveries to the site can start as soon as the frame is ready. Curtain walls require careful inspection during installation to be sure there are no defects in workmanship. Even small imperfections can lead to large, expensive problems later. As work progresses, installed portions of the curtain wall can be checked for water leakage according to AAMA 501.2. This involves directing water at the joints in the wall with a hose that has a specified nozzle and following specified procedures to isolate the causes of any leaks. Where thought necessary more elaborate instrument field test for water and air leakage can also be done.
Thermal Performance
The thermal properties of curtain wall systems are most commonly tested according to AAMA 1503, for thermal transmittance and AAMA 507 for solar heat gain coefficient, visible transmittance and condensation resistance although comparable NFRC standards may also be sometimes be used.
Curtain wall systems are adaptable to a great variety of glass types, frame sizes and configurations. For this reason, determining precise U factors and other properties for a particular system design usually requires more detailed analysis than, for example when standard window configurations are specified.
Where impact or blast resistance is required, curtain wall systems can be tested to the same curtain wall test standards for doors and windows.
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