A method for human-centered appraisal of façade design for serviceability

Abstract

In the wake of the climate crisis, the building industry faces a unique challenge - to strike a balance between global sustainability challenges and the high standards of human comfort. A building’s façade plays an important role in reducing operational carbon emissions in a building, while maintaining acceptable levels of indoor comfort. In doing so, contemporary façade solutions often lead to an increase in embodied carbon in a building. Further, strategies to reduce embodied carbon, such as use of recycled or reused glass fail to meet conventional standards. This thesis explores the potential of a material efficient approach in design of façade glazing by means of reduction in glass thickness.
Reduction of 1mm thickness of glass can save up to 3 kgCO2eq/m2 of façade area. However, reduction in glass thickness may lead to deformations in glazing well beyond serviceability limits. This may have a negative impact on glazing properties such as its mechanical performance, thermal performance, durability, optical performance, acoustic performance and overall occupant satisfaction. While effects of deformation on objective performance parameters can be calculated and mitigated, there has been no research on how acceptance of deformation in terms of occupant satisfaction can be measured. As a consequence, serviceability limits are mainly governed by objective criteria alone. Occupant acceptance towards deformation has always been assumed to be low and glass panes are designed to be more rigid than may be necessary. Without measurement of occupant acceptance thresholds of deformation it is not possible to perform a comprehensive assessment of limits on deformation, and the potential to reduce glass thickness in glazing.
A novel method has been designed in this thesis to determine occupant satisfaction towards level of deformation in glass; with the intention of arriving at acceptance thresholds comparable to those set by objective criteria. As the first step in research a state-of-the-art review on the subject of serviceability criteria and potential for material efficiency in glazing was conducted by means of a systematic literature review and a façade industry survey. Based on the findings from the review an experiment was designed and developed. The proposed method is designed to be conducted in an office environment or a laboratory with volunteers who are asked to indicate their level of satisfaction towards deformations in glass. The deformations in glass are created by varying air pressure inside the cavity of an insulated glazing unit (IGU) using an electro-pneumatic system designed for this experiment to replicate two common loading conditions related to serviceability – climate loading and wind loading. Preliminary tests were able to provide a sufficient proof of concept for the experimental setup.
Feasibility tests for the experimental setup were conducted wherein the mechanical behavior and optical behavior of glass under deformation was objectively measured. The deformation patterns in glass panes displayed geometrically nonlinear behavior in line with predictions of finite element analysis. It was also found that the static deformation (pillowing) does not have any perceivable impact on the view through the façade panel. However, deformation of glass is perceived through distortion of the reflected images, such as ceiling lights and reflecting objects. Further objective optical experiments must be conducted under dynamic loading conditions so as to compare these with results of subjective testing. Subjective testing of the experimental method with a few volunteers is required before conducting the final experiment.
A novel method was thus formulated for a human-centered appraisal of façade glazing deformation. A comprehensive understanding of impact of glazing deformation is necessary to explore the potential of material efficiency in façade glazing. The experimental setup was found to be versatile and scalable enough to conduct multi-objective experiments to assess the impact of deformations on mechanical behavior, thermal performance, acoustic performance and durability.