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Austin Bensend • Tom Peterson
Over the past two decades, the art of cold-forming glass has grown from an unknown approach to a widely accepted strategy for achieving an array of singly-curved (cold-bent) and doubly-curved (cold-warped) façade surface geometries. Cold-bending and cold-warping are not solutions for all curved geometries, nor should they be blindly adopted without careful consideration to the constraints that will drive their successful implementation on a façade. For the right project, however, cold-bending or cold-warping can prove to be elegant and effective solutions.
This study will include some insightful strategies for managing the geometric complexity and technical challenges for successful delivery of a cold-warped glass façade program. The discussion will include some common principles of cold-warping and will extend to a review a custom cold-warped façade solution utilized on a new facility for a prestigious educational institution in Southern California.
Advanced analysis and design tools, including the integration of various design constraints into three-dimensional modeling software are included in the discussion. The application of recent research topics regarding surface stability, deformation response, and frame member design is also included.
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Yuzhen Zhou
Several years ago, Technoform and the Solar Energy Research Institute of Singapore (SERIS) researched the thermal performance of different aluminum window frames in a hot climate, and the study demonstrates the importance of having thermally broken aluminum window frames for desired thermal comfort. This paper focuses on a similar issue, but with curtainwall systems, by simulating typical shadow-box spandrels and obtaining each case's frame and glass temperatures.
The paper discusses that the overheating problem is as critical as the condensation problem; however, both are caused by the thermal bridging effect. Overheating may not only cause thermal discomfort but also affect the durability of the PVB interlayer if the laminated glass is used as the spandrel glass.
For the thermal simulation, summer outdoor temperature and solar irradiance referred to a subtropical climate (Shenzhen, China), and head transoms with different spandrel glass and frame types were modeled using THERM software. The results show that in the worst case, the maximum temperature of the frame and glass edge is 56°C (132°F) and 45.5°C (114°F), and the time duration of the frame temperature exceeding 40°C (104°F) is about 5.5 hours. The results also show that in the best case with external sunshades and high-performance thermal breaks, the frame and glass edge temperature is below 40°C (104°F) all the time.
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Wout Parys • Jelle Langmans • Piet Houthuys • Staf Roels
The development of methods to predict and control moisture accumulation in building envelopes has always been a key element in building science. Today’s existing hygrothermal engineering tools range from simple 1D steady-state heat and vapour transport models (widely known as the GLASER method) up to fully-coupled 2D and even 3D transient Heat Air and Moisture models. There is of course a trade-off between ease-of-use and accuracy. When hygric inertia, air transport or 2D/3D effects play a major role, predictions based on the 1D Glaser method (as standardised in EN ISO 13788) drift aways from reality. To obtain more realistic results, one should move to more advanced hygrothermal models considering the mentioned effects. When correctly used, advanced hygrothermal simulation result in highly detailed results. However, these advanced hygrothermal models often are considered too complex for day-to-day engineering work in the early design stage.
To fill this gap, the present article presents a practical 3D heat and vapour model to estimate the risk for interstitial condensation in building enclosures. The model is in fact a three-dimensional implementation of the Glaser method, including the calculation of moisture accumulation and drying in consecutive monthly periods.
The first part of this article outlines the modelling assumptions and solution technique. Thereafter, the model is validated against a 2D example from the literature and the 1D example from EN ISO 13788.
The article ends with an actual case whereby the applicability of the model is demonstrated by making design decisions for the energy-efficient retrofit of a curtain wall system.
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