Fenestration systems, being the transparent and translucent part of the building envelope, have traditionally been identified as the weak point of the building and, simultaneously, as a key element to pursue higher building performance in terms of energy use and occupant comfort. Due to the role of the transparent part of the building envelope in regulating heat and mass transfer, it has a significant impact on building performance (building whole-life carbon and costs, overall energy use and Indoor Environmental Quality) while providing opportunities to respond to different and contrasting building performance requirements and functionalities at the same time (e.g., view out, daylight and solar control). In office building architecture, glass fenestration systems have gained popularity since the rise of modernism. Traditional glass façades, however, have many implicit disadvantages. The most relevant in this context include poor thermal insulation properties for winter conditions and high overheating risks, even in extremely cold climates in sunny conditions. In noisy environments, poor acoustic insulation can also be a significant drawback.

During the last two decades, sustainable building design has rapidly moved towards a design approach aiming to design innovative high-performance façade systems able to provide high thermal insulation and react to the outdoor environment and occupants’ requirements to reduce building energy demands and enhance thermal and visual comfort with a proven increase in productivity. Such an innovative adaptive façade technology, the Closed Cavity Façade (CCF), has been studied in this project, emphasising its thermal, visual and comfort performance for various climates.

This research project, titled ‘Optimisation of Closed Cavity Façade to Enhance Energy Performance and Indoor Environmental Quality in Office Buildings’, embarks on an in-depth exploration of glazing technologies within the realm of sustainable architecture. It systematically assesses how variations in glazing parameters, such as U-value, SHGC-value, and VT-value, impact energy consumption and indoor comfort in office buildings across different climates. The study integrates simulation-based sensitivity analysis and multi-objective optimisation to identify optimal glazing configurations, balancing energy efficiency and occupant comfort. This research advances the understanding of Closed Cavity Façades in energy-efficient building design. It proposes practical applications and future research directions, emphasising the importance of incorporating local climatic factors into sustainable architectural practices.

The project commences with a comprehensive review of glazing technologies used in building façades and then of Closed Cavity Façade (CCF) technology, emphasising their role in modern sustainable architecture. Each chapter progressively builds upon this foundation, exploring the dynamic interplay between glazing characteristics and building performance. The research highlights the significant influence of U-value, SHGC-value, and VT-value on total site energy consumption and Predicted Percentage of Dissatisfied (PPD), a standard for assessing thermal comfort.

Through an innovative approach developing a combined simulation-based sensitivity analysis and multi-objective optimisation tool/framework, the study reveals striking variations in optimal glazing configurations across different climatic zones. These findings provide critical insights into how specific adjustments in glazing properties can lead to substantial improvements in energy efficiency and occupant comfort, particularly in office buildings. The research methodologically assesses various simulation models and optimisation strategies, ensuring robust and reliable results. Chapters focusing on multi-climate assessments illuminate the necessity of tailoring glazing designs to specific climatic conditions, thus challenging the one-size-fits-all approach in façade design. The project culminates in a series of optimisation exercises across nine climatic conditions. These exercises employ advanced algorithms to extract Pareto front of optimal solutions, balancing minimising energy consumption and reducing occupant discomfort as measured by PPD.

Optimisation of various configurations of CCFs with triple-glazing unit (TGU) or double-glazing unit (DGU) as inner skin on the model of an office-like experimental facility for different types of climates led to an improvement of energy performance in the range of 18-37% or 21.8-40.7% compared to the traditional TGU or DGU respectively used as the baseline, depending on the CCF configuration and the climate. In addition, the improvement of the users’ comfort using a CCF was confirmed through Fanger’s comfort indices, with PPD and PMV being less than 10% and in the range of -0.5 to 0.5, respectively.

In conclusion, this research project significantly contributes to the field of sustainable architecture. It provides a thorough understanding of the glazing parameters influencing building energy performance and indoor environmental quality and proposes a novel approach to optimise these parameters in office buildings. The results are statistically significant and offer practical implications, guiding architects and building designers in their quest for more sustainable and comfortable buildings. The outcomes of this study serve as a valuable guide for future research, especially in exploring innovative glazing technologies and their application in diverse climatic conditions.