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Lighting is often completely left out of architectural plans ! Only when the electrician starts throwing in cans where he thinks it will work - is your lighting plan figured out!
Simple common sense helps figure out a good deal of lighting design.
Day lighting optimizes natural sunlight entry into a building to minimize the need for artificial lighting.
Artificial lighting is produced by electricity.
Energy -efficient lighting is the use of artificial light to receive the optimal level of light for the lowest energy investment.
Task lighting serves a limited area where a person's "work" is concentrated.
The central concern associated with day lighting is the heat gain that can result when natural light is brought into a home. In our region, California, this is an especially important concern. During the heating season, the heat gain from natural light can be useful.
Another concern with natural light is the ultraviolet (UV) rays in natural light. When natural light strikes fabrics and some other materials, the UV rays can discolor and weaken the material. For clients with expensive wardrobes it might be crucial not to have windows in the closets.
Simple design strategies and certain materials facilitate the energy saving advantages of natural light. Light colored interiors and open floor plans are good choices. This approach also augments artificial light efficiency.
Energy efficient lighting is not simply finding the most light for the least wattage or the longest lasting light bulb. Proper sizing of the light to the needs of the location and the tasks that will be performed, called task lighting, is an energy saving strategy.
New technologies are being developed in the field of transparent insulation which would minimize heat gain from direct natural light. There are presently good design approaches and materials in day lighting and artificial lighting.
Energy efficient lighting products are readily available. Day lighting products are rare.
Energy efficient lighting products have a higher initial cost but show excellent paybacks in areas where lights are heavily used. Day lighting strategies can have a wide range of cost impacts.
There is a larger appeal to the aesthetic enhancements that can be associated with day lighting.
1.0 DAY LIGHTING
The primary goal in day lighting is to bring in indirect light (light that is reflected and not in a direct line to the sun).
To accomplish this, overhangs on windows, which are a primary means of day lighting, must be sized to prevent direct light (light that is in direct line to the sun) from entering except, where desired, in the heating season.
A clerestory is a design feature suitable for open plan homes with a ceiling following the roofline. The clerestory is a windowed raised section of roof, typically consisting of operable windows, for light and ventilation. The most appropriate orientation is north or south.
Side lighting from a window is the most common source of day lighting. The amount of light decreases exponentially as you move toward the interior of the room. Light colored walls and ceilings that can reflect light in a diffuse manner will aid the effectiveness of the natural light.
Horizontally-oriented windows high on a wall will permit the best penetration of light into a room.
Reflected light can be achieved with light shelves and louvered window coverings. The primary drawback is that direct light is needed. Venetian blinds with a reflective coating on the top surface of the slats can be angled to bounce the light to the ceiling. A light colored ceiling will illuminate from the reflected light. A horizontal reflective surface placed near the top of a window (light shelf) will similarly reflect light to the ceiling and deep into a room.
Reflecting direct light to the ceiling reduces glare and provides effective deep penetration of natural light.
Skylights are generally sources of excessive heat gain in our area. They can also cause excessive heat loss in the winter. The following guidelines will help you use skylights advantageously:
Use a translucent glazing which reduces glare.
If using clear glazing, use a ceiling diffuser at the bottom of the skylight shaft to improve light distribution.
At the minimum, use double glazing.
Provide an interior insulating shade or panel to seal off the skylight shaft from nighttime winter heat loss unless special highly insulating glass is being used.
Use an exterior shading system over the skylight during the summer.
There is a skylight product specifically designed for day lighting purposes. It uses a pipe with a reflective interior to bounce the light down the pipe to a ceiling diffuser from an acrylic dome skylight on the roof. This is a method to bring natural light to a dark interior area of a home without constructing a costly light well.
ENERGY EFFICIENT LIGHTING
The primary strategy in energy efficient lighting lies in a design that recognizes what will occur in the area to be lit and sizes the lighting to that task. It is also important to consider the quality of the light, which can affect the level of comfort.
The amount of energy needed to produce that amount of illuminance depends on the distance to the light source. With a shorter distance more illuminance will be available in a defined area which is the reason task lighting can be conserving.
A general goal is to minimize the amount of artificial light needed for "background" light (the light needed to pass through or function safely in the house). This can be accomplished with the use of cove lighting. Cove lighting is characterized by the use of ledges, valances, or horizontal recesses that cause the light to be distributed over the ceiling and upper wall. Cove lighting can be provided by low wattage fluorescent lamps or low voltage lights concealed behind a decorative valance in the upper third of the wall. The low wattage fluorescent lamps conserve energy and are long lasting. The reflected light off the ceiling provides even light throughout the room.
In rooms that receive natural light, there can be a frequent varying requirement for artificial light according to how bright it is outside. A fluorescent light with a "day lighting" ballast will vary in light output according to the light needs of the room. The fluorescent light, in this case, is conserving in its light output per wattage and the day lighting ballast is conserving by dimming the light output if natural light levels or other light sources are providing adequate light.
There are two general types of occupancy sensors: infrared and ultra-sonic. Ultra-sonic sensors are best in rooms with partitions or dividers. Infrared sensors are better for open areas. Some sensors include both features. Integrated units that include the sensor and relay in a single housing that fits into a standard electrical box are priced more reasonably for residential applications.
Timers turn lights on and off at predetermined times.
Dimmers will reduce the light level and will only save energy when used consistently.
Natural light when brought into a home in a non offensive way - not too bright or glaring or too hot - contributes to the comfort within a home. The selection of light bulbs for artificial lighting should therefore attempt to combine comfort and energy efficiency.