An Investigation of Daylight Linked Lighting Controls and the Implications to Building Energy and Environment Policies

Daylighting is an effective and sustainable development strategy for enhancing visual comfort, energy-efficiency and green developments. Window openings provide a dual function not only of admitting light for indoor environment with a pleasing atmosphere, but also of allowing people to maintain visual contact with the outside world. Daylight is considered to be the best source of light for color rendering and its quality makes it the one light source that most closely matches the human visual response. People like to have good natural lighting in their living and working environments. Hong Kong (HK) has no indigenous energy resources and most of the imported fossil fuels are for electricity generations. Pollutants produced from the burning of fossil fuels lead to acid rain and human respiratory diseases. Emissions of greenhouse gases (GHG) cause the formation of global warming and climate change. Electricity saved means nonrenewable fossil fuel conserved together with the likely pollutants and GHG reductions. In subtropical HK, most of the electricity is used for creating a thermally and visually comfortable built-environment through air-conditioning and electric lighting representing three quarters of energy consumption in commercial buildings. To encourage energy-efficient building envelope designs, a code of practice for overall thermal transfer value (OTTV) in buildings was legislated. By far, solar heat gain through fenestration is the most important parameter for OTTV determinations. Using appropriate energy-efficient lamp fittings with lighting controls and proper daylighting schemes can help reduce the electrical demand and improve vision efficiency. The energy savings derived through the use of daylighting not only facilitate the sparing use of electric lighting and reduced peak electrical demand, but also reduce cooling loads and offer the potential for smaller air-conditioning plants to be built. The availability of more comprehensive solar radiation and daylight illuminance databases would be invaluable to the determination of building envelop cooling load and evaluation of daylighting designs. However, such basic data for the surfaces of interest are not always readily obtainable. In HK, OTTV is mandatory but daylight-linked lighting controls in buildings are not widely considered. The proposed project establishes extensive solar radiation and daylight illuminance databases via systematic measurements and prediction models, and demonstrates the significance of including daylighting considerations in building designs. The findings will be useful to architects and building engineers to conduct building-facade and lighting designs. More importantly, policy makers can build up more appropriate sustainable policies for buildings.