Prof Dr Meltem YILMAZ DAYLIGHT AND ITS CONTROL

Prof. Dr. Meltem YILMAZ DAYLIGHT AND ITS CONTROL IN SUSTAINABLE ARCHITECTURE

Introduction Daylight While light is a creative medium, its most basic function is to enable us to see. Our visual acuity relies on the quantity of light and its spectral distribution. Seeing is therefore not only about distinguishing light and shade, but also color. The movement of light is a linear process where time and space meet. Any moment reveals frozen movement in time. We have evolved to respond to daily and seasonal change brought about by the movement of the sun, the moon and the stars. Through the passage of light we track the change of day into night as well as form and surfaces moving in light.

In the 20 th century, the electric light has radically changed our way of life. The rhythm of life was for the centuries determined by the cyclical succession of day and night. It was only the emergence of electric lighting that enabled man to break away from this imperative rhythm. All at once, technology gave man the possibility of warding off darkness and imagining a different world. Our modern society is equally dependent on abundantly available artificial light in any place and at any time. It is not only necessary to guarantee the continuity of our activities, but also to give shape and atmosphere to our visual perception of the environment, independent of the availability of daylight.

For all architectural spaces whose envelopes are penetrated by any opening to the exterior environment, lighting design begins with recognition of the entry of daylight. It is a first consideration because the presence of daylight in an interior strongly influences spatial perception and also changes the color of surfacing materials in terms of how they appear elsewhere in the room under a number of different kinds of electric illumination. The amount of sunlight reflected about an interior is determined by the size and shape of apertures in the spatial envelope – as they relate to the proportions of a room. Direct daylight will penetrate deeper into a room the higher the top of the window is above the floor.

Windows can reduce dependence on electric lighting and lower energy costs. Passive solar design calls for south-facing windows, but it is important not to neglect daylighting in other parts of the building. When planning for good daylighting, we have to consider the illumination provided by the sky rather than direct sunlight, which is often undesirable

Good daylighting is not simply a function of the quantity of light. In fact, some techniques that increase the quantity of daylight can actually decrease its quality. The two main quality issues are glare and light distribution. Glare can be either disabling or discomforting. It is disabling when it interferes with the ability to see. It is discomforting when there is excessive contrast between light and dark surfaces in a room. Glare does not nesessarily increase with increasing window size.

Room Finishes: For maximum daylight levels, uniformity and the least glare, room surfaces should have matte finishes. Shiny finishes create reflections that result in glare.

Glass Type: Glazing that allows the highest transmission of the visible portion of the solar spectrum provies the highest daylight levels. Window Position: The higher the window, the greater the Daylight Factor and the deeper the penetration of daylight into the space. Extending the window to the floor does little to increase daylight levels. Clerestory windows that allow deep penetration of daylight while avoiding normal viewing angles are a good daylighting strategy.

While up to the mid-20 th century almost all schools and workplaces used daylight as their primary source of lighting, the advent of inexpensive energy and the proliferation of fluorescent lights in the 1950 s and 1960 s made daylight as an illumination source almost irrelevant. When energy costs began soaring in the 1970 s the ‘glazed skin’ look of many buildings became an expensive, though popular and attractive, liability that often increased the costs of both heating and cooling. Cooling, in particular, was a major cost, leading to the elimination of solar gain-the heat generated by direct natural sunlight through windows. New construction deemphasized direct sunlight and brought forth lower ceilings and lower building skin-to-volume ratios. Dropped ceilings, heavily tinted glass, and insulating panels, designed to reduce heat from windows, gained widespread acceptance.

The net result of this change in architectural and design priorities (and realities) for public buildings of all types has been a dramatic reduction in the amount of daylight available to students in schools and working people at their jobs. Recently, this trend is being reversed for two reasons. First is the cost. Along with heating and cooling expenses, the use of electricity to provide workplace/school lighting adds considerable overhead to the overall cost of operating a building. Not only is daylighting cheaper ( a net energy benefit), it is intrinsically more efficient than any electric source because it provides greater amounts of brightness per unit of heat content (lumen per watt). Second, a growing interest in the influence of the indoor environment on health, productivity and higher retail sales has resulted in growing interest in the potential benefits that day lighting can bring toward reaching these goals.

With the development of sustainable architectural concept, illumination of spaces with day lightning has become more important than ever. The main principles of sustainable architecture are; Energy : the usage of renewable energy. Minimize the consumption of artifical light. Land Use: It is not a ‘commodity’, it is tha base of life. Local Material: Renewable local materials have to be used.

Daylight is generally perceived as more attractive and comfortable than artificial light. There are several reasons for this: Light emitted by the sun covers a wide spectrum of colors. The blend of these colors makes up white daylight. Artificial light sources cannot exactly reproduce the color spectrum of the sun. The eye senses this and reacts by tiring more easily. Daylight is dynamic. It varies through the seasons and times of the day, the position of the sun and cloud cover. Artificial light is static.

The required amount of artificial light in interior space is set at a level required for minimum comfort. Daylight in interior spaces often reaches considerably greater light levels, which is perceived to be more pleasant. Daylight is emitted by all sides of the celestial hemisphere and by the sun. Its distribution results in the illumination of the environment. This kind of illumination is comfortable for the eye.

A further advantage of daylight is its potential for energy saving. All additional daylight not only means an increase in visual comfort, but also an energy saving in artificial lighting. Until recently, this hardly been recognized. Contemporary energy-efficient architecture no longer means merely improving insulation, but intelligent daylight design. The drive to save energy has set off a search for ways to maximize the effective use of daylight while at the same time reducing the associated thermal radiation. The recent association of the two disciplines of daylight planning and indoor climate technology has yet to be put into architectural practice. In addition to the ecological and economic advantages of a good supply of daylight in a building, planned use of natural light enhances design and has appositive effect on the physical and psychological well-being of its users.

Standart Glazing The basic method of maximizing daylight intake to the interiors is glazing. -Daylight transmittion in standart glazing.

In Conventional glazing; Some conflictions can be occurred due to the heat and day lightning problems. These problems can be solved with advanced glazing systems.

Advanced glazing systems have special features, such as selective coatings or low emmisitivity window glazings. They can be specified which are transparent to daylight and are opaque to potentially detrimental UV radiations. One of the sample of advanced glazing systems

Advanced glazing systems; Cut energy consumption, Prevent associated pollution sources, Reduce peak demand, Enhance daylighting performance, Improve occupant comfort. One of the sample of vacuum based glazing system

Other benefits include less air leakage and warmer glazing surface temperatures, which improve comfort and minimize condensation. These high -performance windows feature multiple lights of glass, specialized transparent coatings, insulating gases sandwiched between panes of glass, and improved frames. Issues to consider include: Shading and sun control Visual requirements (glare, view, privacy) Heat gains and losses Thermal comfort Condensation control Ultraviolet control Acoustic control Security issues Color effects Energy requirements Daylight performance

Although the source of daylight is the sun, surfaces and objects within a space reflect and scatter daylight. An increase in visibility and comfort can be achieved through increasing room brightness by spreading and evening out brightness patterns. A reduction in intensity occurs from reflecting and partially absorbing light throughout a space. A light shelf, if properly designed, has the potential to increase room brightness and decrease window brightness.

Advanced Daylight in Take Sytstems Light Shelves Designed to provide sunlight in take and lead the sunlight in to the floors, to provide diffuse lightning. Main goal; taking optimum level of sunlight to illuminate the interiors of the buildings. This illumination is provided with small shelfs which act as an illumination source.

Basic Principles of Light shelves Typical Light Shelf Sample

Light shelves can be used with artificial lights. Light shelves interior The positions of the light shelves, depend on the volume of the spaces to provide indoor-outdoor relations and to prevent glare. If the shelves are positioned far to ceiling, more light can be taken. Sometimes according to needs, solar light reflections are used with artificial light sources, so same homogenous lightning levels can be obtained at both day and nights.

Dynamic Light Shelves System Shelves are movable so, direct light glare can be prevented and also reaching of sunlight in to the deep of the room is provided. Two groups; Manuel Systems: users arrange the positions of the shelves according to seasons, months etc. according to the sun’s position. Automatic Systems: a micro computer arrange the positions and angles of the shelves according to seasons to provide efficient illumination. ○ Disadvantages of this sytstem are cost expensive and needs more space for technical staff. Also, it uses electrical components so there may be some break downs in system.

Basic Principles of Dynamic Light Shelves Two factors directly effect the positions and efficiency of light shelves. Climate Latitude and longitude coordinates of buildings

Day Light Transmitting Systems are especially used in buildings that have insufficient or no openings such as windows, skylight etc. . In light shelves, daylight is taken into interior directly, but in transmitting systems, daylight is taken from one point, collected and distributed to the spaces.

1 - Light Tubes emitting of daylight from one optical staff and transmitting to the spaces. This system is successful at especially deep spaces such as large office buildings. made up in three parts; Collector; positioned on rooftops. Hemi sphere shaped optics or a tube take in or collects the daylight. Transmitter Distributer

Diagram of Light tube system. diagram Daylight in taking and illumination Compare with the light shelves, light tubes have more complex mechanisms and they need more structural spaces such as small skylight etc. In spite of this when it is thought in a long term, light tubes can be economic and effective for the wide and multiple spaces than the light shelves.

Parts of typical Light tube system Light Tubes on roof Illumination with Light tube system Polycarbon Optic Light Tubes

2 - Fiber Optics Fiber optics are, optical specified fibers that can transmit and lead the light rays even through the long ranges. Basic principle of fiber optic based lightning is close to the light tube systems. Solar panels or heliostatic units that are positioned on the roof tops collect daylight that is transmitted with fiber optic cables, then daylight is transmitted to light tubes. These tubes are directly related with special lightning source to illuminate the spaces at day times.

Solar panels or heliostatic units that are positioned on the roof tops collect daylight that is transmitted with fiber optic cables, then daylight is transmitted to light tubes. These tubes are directly related with special lightning source to illuminate the spaces at day times. Fiber optic daylight systems are more efficient than many daylight in take systems. Also there is occurred less light losses so more daylight is used for illumination as much as possible. However, sensitive structures of fiber optic cables may occur some problems and cost of treatment can be higher than the other systems. Solar panels of fiber optic system Illumination with fiber optic system

3 - Anidolic Systems Different from the light tubes, anidolic systems do not collect the sun light. Their work principle is; absorbing sunlight with a glass semi optics unit than transmitting to the ceiling system. In this system sunlight is transmitted directly, there are no collectors, reflectors or mirrors. Altough their simple mechanism anidolic systems must be used with their special ceiling systems, for this reason their field of use is limited and sometimes that can be less economical than the other systems.

Altough their simple mechanism anidolic systems must be used with their special ceiling systems, for this reason their field of use is limited and sometimes that can be less economical than the other systems. Illumination principle of Anidolic system Anidolic Sytem on the upper side of a window

4 - Other Systems Besides of commonly used daylight in take systems, also there are new designed daylight in take systems that are used in sustainable architecture. Some of them are; Holographic optic panels, prismatic panels, special glass types etc… Holographic panels are; carving of special designed textures to a laminated glass with laser technology. These panels have specific features to emit sunlight as much as possible. Holographic panels are assembled on the facades of the buildings, they take the daylight with two ways and directly transmitted to ceiling and illumination system. As a light emitting system holographic panels are efficient, however cladding of hole surfaces with these panels and maintenance problem may limit the using of this system. Prismatic featured panels, special glass panels have similar features with holographic panels. They have same advantages or disadvantages however many of types are suitable for using in hot climate conditions.

Prismatic featured panels, special glass panels have similar features with holographic panels. They have same advantages or disadvantages however many of types are suitable for using in hot climate conditions. Holographic Panel Prismatic Panel cladding

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