Daylighting Methods in Architecture
There are many different types of daylighting as mentioned in my previous post. I thought that I would ellaborate a little more on yesterday and it will also help me get a better understanding or make a decision on the type of daylighting that I would like to use in the design of my building.
Windows are the most common method of admitting light into a space. Their vertical orientation means that they selectively admit sunlight and diffuse daylight at different times during the day and the year. Therefore, windows on multiple orientations must usually be combined to produce the right combination of light for the building, depending on the climate and geographical location. Different types and grades of glass with different window treatments can also affect the amount of light transmission through the windows into a space. The type of glazing is an important issue to consider when designing or changing a building.
Another important element in daylighting is the use of clerestory windows which are high, vertically placed windows. They can be used to increase direct solar gain when oriented towards the equator. When facing toward the sun, clerestory windows and other windows may admit unacceptable glare. Alternatively, clerestory windows can be used to admit diffuse daylight that evenly illuminates a space such as an office or studio. Quite often, clerestory windows also shine onto the interior wall surfaces painted white or another light colour. These walls are placed so as to reflect indirect light to interior areas where it is required. This method has the advantage of reducing individual directions of light to make it softer and more diffuse which reduces shadows.
Skylights and Roof Lanterns
Skylights are light transmitting fenestration which is glazing products filling openings in a building which also includes windows, doors, etc. forming all, or a portion of, the roof of a building space. Skylights are often used in the daylighting design of residential and commercial buildings, mainly because they are the most effective source of daylight based on unit area. There is an alternative to a skylight which is a roof lantern that sits above the roof as opposed to a skylight which is fitted into the construction of the roof. Roof lanterns serve as both an architectural aesthetic feature and a method of introducing natural light into a space, and are typically wooden or metal structures with glazed glass panels.
Another roof-angled glass alternative is a sawtooth roof (which is usually found on older factories). Sawtooth roofs have vertical roof glass facing away from the equator side of the building to capture diffused light (as opposed to the more harsh direct equator-side solar gain). The angled portion of the glass-support structure is opaque and well insulated with a cool roof and radiant barrier. The sawtooth roof’s lighting concept partially reduces the summer skylight problem, but still allows the warm interior air to rise and meet the exterior roof glass in the cold temperature, with a significant undesirable heat transfer.
An atrium is a large open space located within a building. It is often used to light a central circulation or public area by natural daylight admitted through a glass roof or wall. An Atrium provides some daylight to adjacent working areas, but the amount is often small and does not penetrate the other spaces very far. The main function of an atrium is to provide a visual experience and a degree of contact with the outside for people in the working areas. The daylighting of successive storeys of rooms adjoining an atrium is interdependent and requires a balanced approach. Light from the sun and sky can easily penetrate the upper storeys but is more difficult for the lower, which rely primarily on light reflected from internal surfaces of the atrium such as floor-reflected light, so reflective materials need to be considered within the design. The upper floors need less window area than the lower ones, and if the atrium walls are light in colour, the upper walls will reflect light toward the lower floors.
It is possible to provide some daylight into spaces that have low possibility of windows or skylights through remote distribution devices such as a light tube. Remote natural daylight distribution systems could be inherently inefficient and the further they have to transmit the daylight and the more convoluted the path, the inefficiency is increased. The efficiency of many remote distribution systems can also vary dramatically from bright sunny clear to overcast skies. Nevertheless, where there is no other possibility of providing natural daylight into a space, remote distribution systems can be appreciated as an alternative.
Light Reflectors and Shelves
Light shelves are an effective way to enhance the lighting from windows on the equator-facing side of a building, this effect being obtained by placing a white or reflective metal light shelf outside the window. Usually the window will be protected from direct summer sun by a projecting eave. The light shelf projects beyond the shadow created by the eave and reflects sunlight upward to illuminate the ceiling. This reflected light can contain little heat content and the reflective illumination from the ceiling will typically reduce deep shadows, reducing the need for general illumination. In cold temperatures, a natural light shelf is created when there is snow on the ground which makes it reflective. Low winter sun reflects off the snow and increases solar gain through equator-facing glass by one- to two-thirds which brightly lights the ceiling of these rooms. For glare control blinds may be required.
Daylight Redirecting Window Film (DRF)
The Daylight Redirecting Window Film (DRF) applied to windows is a relatively new alternative to Light shelves. DRF is applied to the upper section of a window (clerestory or daylighting position). The principle method of light redirection is by Total Internal Reflection (TIR) of light transmitted through the microscopic elements of the film. When sunlight or skylight penetrates the film, internal microscopic “louvers” redirect the incoming light upward to the ceiling, where the typical ceiling redistributes the diffused daylight deeper into the interior space. As the window film does not alter the architectural nature of the building, Daylight Redirecting Film is an elegant and easy upgrade.
Another type of device used for daylighting a space is the light tube, also known as a tubular daylighting device (TDD), which is placed into a roof and admits light to a focused specific area of the interior. These somewhat resemble recessed ceiling light fixtures. They do not allow as much heat transfer as skylights because they have less surface area. These light tubes use modern technology to transmit visible light through opaque walls and roofs. The tube itself is a passive component consisting of either a simple reflective interior coating or a light conducting fibre optic bundle. It is frequently capped off with a transparent, roof-mounted dome “light collecting dome” and finished with a diffuser assembly that allows the daylight into interior spaces and distributes the available light energy evenly around the space.
Fibre Optic Concrete Wall
Another method of daylighting a space is to make a secure structural concrete wall translucent by embedding optical fiber cables into it. Daylight (and shadowy images) can then pass directly through a thick solid-concrete wall allowing natural daylight into the space.
Smart glass is the name given to a class of materials and devices that can be switched between a transparent state and an opaque state, translucent, reflective, or retro-reflective. The switching is done by applying a voltage to the material, or by performing some simple mechanical operation. Windows, skylights, etc., that are made of smart glass can be used to adjust indoor lighting, compensating for changes of the brightness of the light outdoors and of the required brightness indoors.
Which are Present in the Building and What will be used in the Design?
As it is important for the design to get a lot of natural light into the building where possible due to its use, it is important to look at the current daylighting methods within the building and my intentions for daylighting methods within the design.
Currently, within the structure of the building, there are windows throughout all floors, with not much natural light able to enter the basement. These windows are of different sizes and are single glazed glass, so are not particularly energy efficient. On the roof of the North side of the Second floor of the building, there is a space with windows surrounding it on three sides and the central part of the roof is a large skylight. There are a couple of smaller skylights in the building also.
All of the windows will be changed to triple glazed glass which will be discussed more in the sustainability post, this will make the building more energy efficient. Additionally, the size of some of the windows at the front of the building will be increased to allow more light into the building. I am also considering using the Daylight Redirecting Window Film (DRF) which has the internal louvres to redirect incoming light. Louvres were originally used in the building, so would be a modern link back to the old. There is also a the new addition of the glazed circulation space which forms and extension and insertion to the building to get light into all levels of the building. This will have the addition of possibly some aluminium fins to prevent too much heat gain. I am also considering using smart glass for the glazed element to compensate for changes in the light.