Volume 39, Issue 4 (July 2011)
Controlling Condensation Through the Use of Active and Passive Glazing Systems
Special building occupancies, those with a high interior relative humidity, have a specific set of performance requirements to control condensation for exterior window and curtain wall systems. High levels of humidity, if not properly accommodated by glazed exterior wall systems, can result in condensation on and within glazing systems and adjacent construction. The performance of glazing has typically been viewed and analyzed based on overall system performance that generally results in a set of values that do not apply to project specific applications. With this approach, important aspects of a system, as applied to specific buildings, are often overlooked. In this circumstance, the result too often is unacceptable levels of condensation. Unfortunately, many within the design, manufacture, and construction communities do not fully understand the importance of treating each building for the unique set of conditions that it is, and the resultant consequence of not analyzing and treating each humidified building as a unique set of materials, systems, and environmental conditions. Similarly, the analysis methods and tools necessary to predict and prevent condensation are even less familiar within the design and construction industry. As a result, deficient systems and materials may often be installed in these applications, resulting in failures ranging from minor inconvenience to complete loss of service. There are, however, methods that can be used to reduce or eliminate such problems. This paper describes methods and procedures that can be utilized to understand and identify the performance levels required for high humidity spaces and analysis methods (including computer modeling) to predict performance of systems and materials, and this paper also describes both active and passive technologies that have been successful in meeting these needs. Passive design, through the use of high performance glazing, and active technologies, such as heat tracing and heated glass, are considered. Benefits, risks, and appropriate uses of each are identified. Examples are included to illustrate these approaches.