Directionally selective shading control in maritime sub-tropical and temperate climates: Life cycle energy implications for office buildings

Scheduling directionally selective shading devices to increase or decrease their level of occlusion relative to the total incoming solar radiation has the benefit of controlling solar heat gain during a variety of sky conditions and allowing more constant illuminance levels to be achieved within a building. In this study, hourly sky condition and annual solar angles were used to describe the tilt of the slats of an external directionally selective shading control for an external venetian blind on an office building in Melbourne and Brisbane, Australia. The life cycle energy demand associated with this shading control was compared to a static base case with an external overhang and internal venetians. The analysis was extended to the HVAC system which was sized to account for the effect of the shading on solar gain and the artificial lighting requirement. It was found that the embodied energy of the HVAC and shading components accounted for between 21.7% and 25.5% of the total life cycle energy of these systems over 25 years. There was a reduction in embodied and operational energy requirements over a 25 year life cycle for the external venetian blind control of 24.9% for Melbourne and 24.0% for Brisbane relative to the static base case. Based on the simulation results, office buildings with equator facing facades located in similar climates and latitudes may have the potential for equivalent life cycle energy reductions when external directionally selective shading controls are employed to moderate overheating and daylighting.