A skylight (sometimes called a rooflight) is a light-permitting structure or window, usually made of transparent or translucent glass, [1] that forms all or part of the roof space of a building for daylighting and ventilation purposes.
A skylight (sometimes called a rooflight) is a light-permitting structure or window, usually made of transparent or translucent glass, [1] that forms all or part of the roof space of a building for daylighting and ventilation purposes.
Open skylights were used in Ancient Roman architecture, such as the oculus of the Pantheon. Glazed 'closed' skylights have been in use since the Industrial Revolution, when advances in glass manufacturing made them practical. Since the mid-20th century, mass production of skylights has brought them to many more uses and contexts. Energy conservation has brought new motivation for installing skylights, design innovations (including options in light transmission), and skylight efficiency ratings.
Skylighting types include roof windows, unit skylights, tubular daylighting devices (TDDs), sloped glazing, and custom skylights. Uses include:
An unglazed hole in a roof.
A fixed skylight consists of a structural perimeter frame supporting glazing infill (the light-transmitting portion, which is made primarily of glass or plastic). A fixed skylight is non-operable, meaning there is no ventilation.
An operable (venting) unit skylight uses a hinged sash attached to and supported by the frame. When within reach of the occupants, this type is also called a roof window.
A retractable skylight rolls (on a set of tracks) off the frame, so that the interior of the facility is entirely open to the outdoors, i.e., not impeded by a hinged skylight. The terms retractable skylight and retractable roof are often used interchangeably, though skylight implies a degree of transparency.
Active daylighting uses a tubular daylighting device (TDD). Solar tubes, sun tunnels, or tubular skylights consist of a roof-mounted fixed unit skylight element, condensing sunlight, distributed by a light conveying optic conduit to a light diffusing element. [3] Being small in diameter, they can be used for daylighting smaller spaces such as hallways, and bounce light in darker corners of spaces. TDDs harvest daylight through a roof-mounted dome with diameters ranging from about 10 inches for residential applications to 22 inches for commercial buildings. Made from acrylic or polycarbonate formulated to block ultraviolet rays, the dome captures and redirects light rays into an aluminum tubing system that resembles ductwork. [4] [5]
Sloped glazing differs from other "skylights" in that one assembly contains multiple infill panels in a framing system, usually designed for a specific project and installed in sections on site.
Pavement lights are walk-on skylights. They are set into sidewalks, open areas, and well-lit interior floors as laylights. [6]
Prism lights are sometimes used as skylights; they redirect the light passing through.
Solar architecture means designing buildings to use the sun's heat and light to maximum advantage and minimum disadvantage, especially in the sense of harnessing solar power. Skylights are widely used in designing daylighting for residential, public, and commercial buildings. Increased daylighting can result in less electrical lighting use and smaller sized window glazing (sidelighting), saving energy, lowering costs, and reducing environmental impacts. Daylighting can cut lighting energy use in some buildings by up to 80%. [7]
Toplighting (skylights) works well with sidelighting (windows) to maximize daylighting:
Even on overcast days, toplighting from skylights is three to ten times more efficient than sidelighting. [8]
Many recent advances in both glass and plastic infill systems have greatly benefited all skylight types. Some advances increase thermal performance, some are focused on preserving and utilizing daylight potential, and some are designed to enhance strength, durability, fire resistance and other performance measures.
Contemporary skylights using glass infill (windows) typically use sealed insulating glass units (IGU) made with two panes of glass. These types of products are NFRC-ratable for visible transmittance. Assemblies with three panes can sometimes be cost-justified in the coldest climate zones, but they lose some light by adding the third layer of glass.
Glass units typically include at least one low emissivity (Low-E) coating applied to one or more glass surfaces to reduce the U-factor and especially SHGC by suppressing radiant heat flow. Many varieties of Low-E coatings also reduce daylight potential to different degrees. High purity inert gas is frequently used in the space(s) between panes, and advances in thermally efficient glass spacing and supporting elements can further improve thermal performance of glass-glazed skylight assemblies.
Plastic glazing infill is commonly used in many skylights and TDDs. These assemblies typically contain thermally formed domes, but molded shapes are not uncommon. Domed skylights are typically used on low slope roofs. The dome shape allows for shedding of water and burning embers.
Plastics used in skylights are UV stabilized and may feature other advances to improve thermal properties. Lack of accepted standards for measuring light transmittance is a disadvantage for comparing and choosing skylights with plastic glazing.
Acrylic is the most common plastic glazing used for dome skylights. However, Polycarbonate and Copolyester materials are also used as glazing, where additional properties such as impact resistance may be required. [9]
NFRC: rating for visible transmittance
U-factor: expresses the heat loss performance of any building assembly.
SHGC–Solar Heat Gain Coefficient: measures the assembly's transfer of heat from outside to inside that is caused by sunlight.
These properties are labeled in the U.S. as a decimal between zero and one, with lower numbers indicating lower heat transfer rates. Depending on the geographic region, optimal U-factor and SHGC performance will vary. In the sunny southern climate zones, a lower SHGC is more important than lower U-factor. In the cooler northern climate zones, lower U-factor is more important, and higher SHGC can be justified.
In selection of skylights, a balance is sought between low U-factor and optimal SHGC values, while preserving enough daylight supply to minimize artificial light use. Automatic light sensing controls for electric lighting maximize energy savings.
A study concluded that students have significantly higher test scores in classrooms that optimize daylighting, than classrooms that do not. [10] Other studies show that daylight positively affects physiological and psychological well-being, which can increase productivity in many contexts, such as sales in retail spaces.[ citation needed ]
In terms of cost savings, U.S. DOE reported that many commercial buildings can reduce total energy costs by up to one-third through the optimal use of daylighting. The majority of commercial warehouses and 'big box stores' built in recent years have used skylights extensively for energy/costs savings.
A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent material, a sash set in a frame in the opening; the sash and frame are also referred to as a window. Many glazed windows may be opened, to allow ventilation, or closed to exclude inclement weather. Windows may have a latch or similar mechanism to lock the window shut or to hold it open by various amounts.
A Trombe wall is a massive equator-facing wall that is painted a dark color in order to absorb thermal energy from incident sunlight and covered with a glass on the outside with an insulating air-gap between the wall and the glaze. A Trombe wall is a passive solar building design strategy that adopts the concept of indirect-gain, where sunlight first strikes a solar energy collection surface in contact with a thermal mass of air. The sunlight absorbed by the mass is converted to thermal energy (heat) and then transferred into the living space.
In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unlike active solar heating systems, it does not involve the use of mechanical and electrical devices.
Daylighting is the practice of placing windows, skylights, other openings, and reflective surfaces so that direct or indirect sunlight can provide effective internal lighting. Particular attention is given to daylighting while designing a building when the aim is to maximize visual comfort or to reduce energy use. Energy savings can be achieved from the reduced use of artificial (electric) lighting or from passive solar heating. Artificial lighting energy use can be reduced by simply installing fewer electric lights where daylight is present or by automatically dimming or switching off electric lights in response to the presence of daylight – a process known as daylight harvesting.
A solar thermal collector collects heat by absorbing sunlight. The term "solar collector" commonly refers to a device for solar hot water heating, but may refer to large power generating installations such as solar parabolic troughs and solar towers or non-water heating devices such as solar cookers or solar air heaters.
A curtain wall is an exterior covering of a building in which the outer walls are non-structural, instead serving to protect the interior of the building from the elements. Because the curtain wall façade carries no structural load beyond its own dead load weight, it can be made of lightweight materials. The wall transfers lateral wind loads upon it to the main building structure through connections at floors or columns of the building.
Thermal transmittance is the rate of transfer of heat through matter. The thermal transmittance of a material or an assembly is expressed as a U-value. The thermal insulance of a structure is the reciprocal of its thermal transmittance.
Light tubes are structures that transmit or distribute natural or artificial light for the purpose of illumination and are examples of optical waveguides.
Building insulation is material used in a building to reduce the flow of thermal energy. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation. Often an insulation material will be chosen for its ability to perform several of these functions at once.
Solar gain is the increase in thermal energy of a space, object or structure as it absorbs incident solar radiation. The amount of solar gain a space experiences is a function of the total incident solar irradiance and of the ability of any intervening material to transmit or resist the radiation.
Shading coefficient (SC) is a measure of thermal performance of a glass unit (panel or window) in a building.
An Eco-house (or Eco-home) is an environmentally low-impact home designed and built using materials and technology that reduces its carbon footprint and lowers its energy needs. Eco-homes are measured in multiple ways meeting sustainability needs such as water conservation, reducing wastes through reusing and recycling materials, controlling pollution to limit global warming, energy generation and conservation, and decreasing CO2 emissions.
Glazing, which derives from the Middle English for 'glass', is a part of a wall or window, made of glass. Glazing also describes the work done by a professional "glazier". Glazing is also less commonly used to describe the insertion of ophthalmic lenses into an eyeglass frame.
Insulating glass (IG) consists of two or more glass window panes separated by a space to reduce heat transfer across a part of the building envelope. A window with insulating glass is commonly known as double glazing or a double-paned window, triple glazing or a triple-paned window, or quadruple glazing or a quadruple-paned window, depending upon how many panes of glass are used in its construction.
The Horizontal Skyscraper, designed by Steven Holl Architects and completed in 2009, is a mixed-use building located on the outskirts of Shenzhen, China. Situated in Dameisha, Yantian District, the complex includes offices for Vanke Co., a conference center, restaurant, an auditorium, a hotel, apartments and a large public park.
Passive survivability refers to a building's ability to maintain critical life-support conditions in the event of extended loss of power, heating fuel, or water. This idea proposes that designers should incorporate ways for a building to continue sheltering inhabitants for an extended period of time during and after a disaster situation, whether it be a storm that causes a power outage, a drought which limits water supply, or any other possible event.
In building engineering, a climate-adaptive building shell (CABS) is a façade or roof that interacts with the variability of its environment in a dynamic way. Conventional structures have static building envelopes and therefore cannot act in response to changing weather conditions and occupant requirements. Well-designed CABS have two main functions: they contribute to energy-saving for heating, cooling, ventilation, and lighting, and they induce a positive impact on the indoor environmental quality of buildings.
The David and Lucile Packard Foundation Headquarters is the corporate headquarters of the David and Lucile Packard Foundation, located in Los Altos, California. The Packard Foundation was created in 1964 by David Packard and his wife Lucile Salter Packard, one of the top 100 grant-making foundations in the United States, with the goals of improving the lives of children, enabling the creative pursuit of science, advancing reproductive health, and conserving and restoring the Earth’s natural systems. The David and Lucile Packard Foundation Headquarters is designed by EHDD to be the largest net zero energy building in California, and it has successfully reduced the energy use by 65% over conventional buildings.
Quadruple glazing is a type of insulated glazing comprising four glass panes, commonly equipped with low emissivity coating and insulating gases in the cavities between the glass panes. Quadruple glazing is a subset of multipane (multilayer) glazing systems. Multipane glazing with up to six panes is commercially available.
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