High density conurbation comes with a lot of economic and environmental benefits including reduced energy consumption, efficient transportation and proper land use, which eventually lead to lower levels of greenhouse emissions. Multistory structures present a better solution of increased density. However, the disadvantages of these structures include increased heat gain as well as loss associated with glazed façade designs. Above all, multistory buildings have limited roof area per occupied floor area leading to reduced capacity for thermal and solar energy exploitation.
Several studies have been done relating to the building envelope, double skin façade designs, and curtail wall systems. The studies have also focused on heat flow and shading effects, and energy performance. However, achieving high energy efficiency in a multistory building demands including energy efficiency measures in the initial design process, which include electricity generation potential as well as optimizing building envelop geometrical design.
Professor Caroline Hachem from the University of Calgary in Canada directed a research on the effect of geometrical design of a façade system on the energy performance of a multistory building. The main aim of the research was to increase the area for building integrated photovoltaic systems and for efficient solar capture of the systems without compromising the heating and cooling of the building. The resulting work is now published in journal, Energy and Buildings.
The authors adopted a south oriented perimeter zone of a 12-storey building in the northern hemisphere, hence the term equatorial facing façade. They carried their study under the climatic conditions of Calgary, Canada, which represented the northern cold climate zone. However, the conclusions of the study can be applied to any climate with few adjustments.
The research proposed a design that assumes a repetitive module relating to the double skin façade system. This form of construction consists of two translucent surfaces which are separated by a cavity allowing exterior and interior air movements within the system. The air cavity as well as the façade interior skin provides a buffer between the exterior and the interior environment. The outer skin can be photovoltaic integrated for electricity generation, while the air circulation within the cavity allows for cooling of the photovoltaic systems and provides heat for space heating.
The research adopted a façade system similar to the box window. The systems contained two skins which were continuous over the building and separated horizontally at every floor and vertically between particular façade modules, creating isolated air cavities.
The study applies a basic principle of the utilization of south facing opaque plates on the outer skins as integrated photovoltaics. An interior glazing skin was also incorporated in the system. Solar panels are more efficient when tilted at an angle with respect to the vertical plan. Therefore, the research introduced a faceted design, which involves multiple folded planar surfaces. Dr. Hachem has investigated this type of folded-plate systems over the last few years, and results were published in a number of journals and international conferences. Saw-tooth is the simplest folded-plate geometry consisting of a single fold, while more complex geometries can be achieved based on pyramids.
The research highlights that deviation from the vertical plan led to an increased in the heating load, however this was counterbalanced by a drop in the cooling load. Above all, this was accompanied by a significant increase in energy generation capacity from the proposed façade photovoltaic-integrated systems.
The innovative design proposed in this study demonstrated high energy performance where the multi-fold design can surpass the potential of the flat façade in annual electricity generation by approximately 80%.
C. Hachem and M. Elsayed. Patterns of façade system design for enhanced energy performance of multistory buildings. Energy and Buildings, volume 130 (2016), pages 366–377.
University of Calgary, 2500 University Dr NW, Canada.Go To Energy and Buildings