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:
Brian Koons, PE is a facade consultant and engineer with interdisciplinary expertise in the areas of structural mechanics, thermal/fluids, and engineering design. He has applied his engineering background to the areas of building science and architectural engineering with a primary focus on glass and aluminum/steel exterior wall systems. Brian’s experience includes design and multiphysics engineering of fenestration systems as well as the development of unique design repair solutions. As a building enclosure consultant for Klein and Hoffman, he works on existing buildings and new construction in Chicago and throughout the Midwest.