A common debate in the curtain wall industry is whether to vent or seal shadow box cavities. To address this, a simplified method is presented herein to assess the cavity pressure-temperature relationship within a sealed shadow box assembly. The goal is to provide a step-by-step approach that can be utilized by a wide audience of architects and designers since experimental testing and advanced computational analysis is not reasonably feasible for all projects. A temperature rise can cause a considerable pressure build-up within a sealed air cavity if the deflection of the glass and metal panels cannot provide an adequate increase in volume. Previous research by others stated the effect of temperature rise on cavity pressure is not significant, however, fails to correctly account for the nonlinear bending behavior of glass and metal panels. Significantly higher cavity pressures are determined when accounting for the nonlinear behavior of these elements. Failure to account for high shadow box cavity pressures can have serious implications such as pressure build-up exceeding design wind loads, long-term loading on glass and structural sealant, and potential rupture of air/vapor barriers. With a simplified method available, elevated pressures can be realized during design development to prevent these unacceptable outcomes.
Simplified Method to Evaluate Shadow Box Pressure-Temperature Relationships
Company: Klein and Hoffman
About the speaker:
Glenn Johnson, AIA QCxP leads K&H’s Building Enclosure Commissioning and Consulting Group and is an Principal at K&H bringing more than 30 years of experience in architectural design, code compliance review, project management and technical oversight of institutional, healthcare, hospitality, commercial office, multi-unit residential buildings, parking structures, libraries, and stadium facilities. Mr. Johnson has commissioned more than $2B of projects and has managed more than 10 million square feet of facility space. His primary expertise leverages the commissioning process for the documentation, analysis, and implementation of energy-saving measures.