Daylight glare mitigation by internal shading devices use and effects on building energy performance

Abstract

Daylight glare arouses buildings’ occupants to insert internal shading devices. When solving glare issues, shading strategies can increase internal temperature and building cooling energy consumption, especially in hot climates. Indoor environmental quality has been treated through architectural and engineering projects utilising spatial-temporal metrics and controls algorithms. This article focused on investigating some interactions between user behaviour, shading devices proprieties, and their effects on building’s luminous and thermal environment. This research aimed to relate daylight glare probability’s reductions through internal shading devices uses, with their effects on the window’s solar heat gain and energy cooling demand. Using building modelling and simulation approach through Rhinoceros 3D 5.0 and plug-ins Grasshopper+DIVA, Daylight Glare Probability (DGP) hourly values were generated for an occupant, 1.5 m away from the window at a side lit-room. The open-access model is a typical private office in the multi-floors building. Window’s solar heat gains and energy cooling demands were recorded using EnergyPlus 8.4 software. The model was simulated in East, West, North and South orientations, at Florianópolis. Subtropical Brazilian city. Starting from ‘without solar control’ cases, 8 controls were applied to 4 internal shading devices: blinds 50°, blinds 0°, curtains and roller shades. Clearer and darker colours were considered by two proprieties sets. From two fixed obstruction modes (100% and 50%), DGPintolerable (>45%) and direct solar radiation (>50W/m²) were applied to proposed monthly, daily and automatic controls. DGPintolerable annual frequencies at uncontrolled condition varied from 30% to 65%. These differences pointed out design guidelines according to façades. It has been confirmed that 0° blinds don’t secure daylight glare and increase energy cooling demand. Dark roller shades, curtains and blinds 50° completely solved glare problems, controlled by ‘always 100% closed’ mode and DGPintolerable based controls. Clear devices still allowed 2% of DGPintolerable frequency. However, clear roller shades contributed to reducing annual cooling demand until 11.5% while other devices achieved until 52% increase. Dark curtains indicated maximum increased in annual window’s solar heat gain (3%). Obtained results allowed identifying some design guidelines to balance daylight glare protection and energy-efficiency, contributing to sustainable building design and low impact architecture.