Moisture Penetration Prevention Strategies And Curtain Wall

Home-Improvement Eliminating moisture penetration is the fundamental task of any curtain wall system. Not surprisingly, water infiltration is the typical deficiency that prompts a curtain wall inspection. As a firm deeply experienced in curtain wall inspection, ODonnell & Naccarato has intimate knowledge of the evolution of curtain wall moisture prevention systems, their unique failure points and anomalies and how to engineer durable maintenance repairs for the varied system failures which the curtain wall inspection regimen uncovers. Knowing the history of curtain wall development, in particular the development of moisture penetration prevention strategies is essential to a comprehensive curtain wall inspection capability. The earliest curtain wall systems were based on the perfect seal principle, an update of the older bearing wall principle of barrier or face-sealed moisture prevention design. The idea was simple: make the perfect seal of the exterior wall face and do away with moisture intrusion. Easier said than done, though! Only absolutely consistent field workmanship in the application of silicone sealant combined with a lack of sealant degradation would allow this system to operate as designed. Curtain wall inspection experience reveals time after time that a breakdown in one of these two factors is inevitable over the life of a building. The perfect seal method is still in use today, as it allows curtain wall inspection and maintenance or repairs to be performed completely from the exterior, without any impact on residents or the finished interior. The second generation of moisture penetration prevention acknowledged the realities that curtain wall inspection regimens pointed out: leaks are inevitable. Design began to focus not on preventing leaks, but controlling and managing the moisture that penetrated the exterior face of the system. Curtain wall inspection history shows that moisture penetration often leads to structural degradation. This new generation was designed to ensure that penetrating water did not result in interior damage. The water is channeled from interior gutters to the exterior through exposed, exterior weep holes. High-wind environments play havoc with this design and curtain wall inspection of this type of system often reveals exterior staining or interior damage as water is not allowed to drain as intended. Third generation curtain wall systems are known as unitized systems. Multiple panels are preassembled in a controlled shop environment which provides a much higher quality sealant application at the exterior face. An inner chamber promotes air circulation and pressure equalization. The ends of the horizontal gutters, which curtain wall inspections often showed to be the points of failure, are dammed and sealed in the shop so that no field work is required. Sophisticated design of seals, gutters and panels enabled fourth generation systems to perfect the pressure-equalization by creating dual air loops within the cavity. By expanding the outer air loop, engineers were able to create a truly pressure equalized gutter space, minimizing infiltration due to wind load. The new systems provided an efficient infiltrated water drainage and negated wind load or moisture on the inner face of the curtain wall. . In assessing a modern building, curtain wall inspection engineers are generally presented with face-sealed, water-managed or pressure-equalized rainscreen systems. Design differences and varied failure pathologies present a complex environment for curtain wall inspection engineers as they investigate each type of system. Moisture penetration resistance involves all the facets of the curtain wall: frame construction and drainage design, glazing, weatherstripping and frame gaskets, flashings and seals. Curtain wall inspection engineers must have intimate knowledge of these and their typical failure scenarios as they survey and assess their capacity to resist the forces that drive moisture penetration: wind pressure differential, surface tension, capillary action, gravity and kinetic energy. In addition to this, seismic loads, structural deflection, thermal deformation, and weathering all play into a well-planned and executed curtain wall inspection and maintenance regimen. Curtain wall inspection engineers note that failure points include: Glazing problems from material decay, moisture or thermal build-up and insulated glass unit problems. Internal gaskets and sealants compromised by structural deflection, chemical/incompatible-component interface degradation and thermal loading. Frame corners seals are major failure points as exterior sealants degrade, thermally induced deformation and structural deflection causing debonding. Perimeter sealants have a typical service life of 10 to 15 years with a proper curtain wall inspection maintenance regimen. About the Author: 相关的主题文章: