Curtain Wall Laboratory Testing Explained
Characteristically, a Curtain Wall is often defined as thin, aluminum-framed wall, containing in-fills of glass, metal panels, or thin stone. Curtain wall frame is attached to the building structure and does not carry the floor or roof loads of the building. Curtain wall & other facade elements require performance testing to evaluate if it’s design principle has been met & is structurally safe, and if it’s assemble and installation can guarantee a good shield for the complete building.
Performance testing of the specimen, both prior to construction, and during construction, is a well-established and respected element of quality assurance. Testing representative segments of curtain wall, or windows, for example, comprises three basic tests, plus three others. The basic tests are: Air Infiltration, Water Penetration and Structural Load.
For these tests an airtight chamber is constructed on one side of the specimen. The Air Infiltration test consists of measuring the flow of air from the chamber and deducting from it the flow of air attributable to the chamber itself. The Water Penetration test consists of creating a pressure differential across the specimen (with the lower pressure on the inside of the specimen), and spraying water uniformly on the exterior. The Structural Load test consists of pressurizing the chamber (both positive and negative) to simulate wind generated pressures. Generally the water penetration test is repeated after the structural load test to ensure the performance has not been affected.
Three additional tests are as follows: The Dynamic Water Penetration test, where air from a large wind generator is directed at the specimen at the same time as the water spray; The Seismic test, where one of the support beams is jacked in three cycles of lateral displacement. The Thermal Cycling Test consists of placing an insulated chamber on the exterior side of the specimen. The temperature in the chamber is varied from ambient to a selected low temperature and then to a selected high temperature over a period of 8 hours, while the temperature on the inside of the specimen is maintained at room value. This simulates either 3 or 7 times annual changes in temperature. The water penetration and/or air infiltration test are conducted again after this procedure.
Mock-up Site testing comprises either a chamber test (much like the mock-up test but generally more limited) or the hose test. These tests are intended to check the workmanship and that the design which passed the mock-up testing is being properly constructed on site. The hose test consists of spraying water at the system following a prescribed procedure and as per international standards.