Thermally induced fracture, known as thermal shock, constitutes a high risk for many glazing applications. The risk is often assessed at pre-construction stage on a project-by-project basis and is mitigated by costly measures, but there is currently no international standard or universally accepted procedure for performing the thermal shock assessment. Consequently, there are many different methods and possible approaches for assessing the risk, ranging from overly-simplified national standards such as ASTM E2431 and NF DTU 39 P3, to very laborious coupled thermal-structural finite element analyses based on point-in-time static or transient boundary conditions. This paper briefly reviews the existing approaches, by assessing their applicability and limitations, and based on these, it presents a novel method for the quantitative assessment of thermal shock risk in glazing systems, by means of a context-specific long-term evaluation. The proposed method is intended for a broad range of architectural glazing systems, including multi-layer glazing element (e.g. insulated glazing Units, effect of fixed and operable shading systems, etc.). It is simple yet sufficiently accurate for day-to-day engineering practice and could be run as a web-based tool. The proposed methodology is applied to various glazing configurations including double and triple glazing units with different optical and solar properties. The results are compared with those obtained from ASTM E2431 and NF DTU 39 P3 standards. It is found that, in contrast to current methodologies, the proposed dynamic model provides a more precise thermal shock risk evaluation by incorporating realistic hourly climatic data and accurate thermal model, this makes it applicable to environmental contexts outside those provided in the national standards, thereby enhancing the global use of the analysis.
Fabio Favoino
ARCHITECTURAL GLASS THERMAL SHOCK ASSESSMENT BY MEANS OF DYNAMIC THERMAL SIMULATIONS
Company: Politecnico di Torino, Italy
About the speaker:
Prof. Fabio Favoino is Associate Professor of Building Physics at Politecnico di Torino. His research, teaching and professional activity focuses on high performance and responsive transparent building envelope technologies and systems, and on performance based evaluation methods for the built environment, such that to support the design and operation of building envelopes combining high indoor quality, energy efficiency and flexibility and low to no impact on the environment.