PASSIVE TUBULAR DAYLIGHT GUIDANCE SYSTEMS ENERGY SAVING POTENTIAL FOR THE RESIDENTIAL BUILDINGS IN ROMANIA

Traditional vertical window can provide adequate daylight within about six meters of the window. Daylight levels decrease asymptotically with distance from the window so that a disproportionate amount of daylight/solar gain must be introduced into the front of the room to achieve small increases in daylight at the back. Tubular daylight guidance systems (TDGS) are linear devices that channel daylight into the core of a building. These consist of a light transport section with, at the outer end, some device for collecting natural light and, at the inner end, a means of distribution of light within the interior. The nature of the systems and the factors influencing the costs and various benefits that contribute value are identified. Lighting systems in residential buildings, lit by electric lighting and daylight guidance, were surveyed. Data on the physical characteristics of the systems and lighting conditions achieved were collected. The results formed the input to a cost and value analysis which permitted the economic limits of the systems to be evaluated. Some estimations were made about the energy savings and the environmental benefits of those lighting systems