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Window coverings are considered any type of materials used to cover a window to manage sunlight, privacy, additional weatherproofing or for purely decorative purposes.
Window coverings comprise materials used to cover a window to manage sunlight, privacy, additional weatherproofing or for purely decorative purposes. Window coverings are typically used on the interior side of windows, but exterior solutions are also available.
Window coverings may be used to manage overheating and glare issues due to sunlight. Designers may consider these variables in the context of visual comfort indices, which include light quantity (sufficient light to perform tasks), direct sunlight (which may lead to overheating), light uniformity (light distribution over the task plane), and glare. [1] Window coverings can provide a sense of privacy. It is important to consider both privacy in terms of the view from the outside in and from the inside out. Poor privacy is often caused when windows are located on the ground floor, or face nearby neighboring high-rise buildings. [2] Nonetheless, if occupants are not satisfied with the privacy the window provides, window coverings will be used to avoid it. Window coverings can also be applied temporarily to protect windows in storm conditions (such as hurricane shutters) or for extra thermal performance in winter to protect against heat loss through windows (such as insulated blinds or window inserts). Window coverings may be selected by building usage and occupant activity in the room. The amount of daylight needed in the room will differ depending on room type. For information on daylighting metrics that may be affected by window covering use, please reference the daylighting page. Aesthetic qualities of window coverings should also be considered, such as how the color, material, and style match the rest of the interior space.
Window coverings can also affect view quality through the windows. View quality can be expressed through three main variables: content (what an occupant sees), access (how much view can be seen from the occupant's position), and clarity (how clearly an occupant can see the content). [3] [4] Partially closing curtains or pulling shades down part-way would affect view quality by limiting view access. Using small aperture shades such as fabric roller shades would primarily affect view quality through a change in view clarity. View clarity can be assessed by visual acuity, contrast sensitivity, and color perception. [3] The color, as well as aperture size, known as Openness Factor, or OF, are two variables of fabric shades that can change view clarity perception. Darker fabric shades with larger openness factors generally achieve higher view clarity. [5]
The impact of window coverings on view quality is of interest for designers, manufacturers, and researchers. However, there is limited research available on the topic of view quality, “due to its complex nature, insufficient funding, and a lack of coordinated effort to move the field forward.” [6]
Types of coverings include:
Window coverings can be static or dynamic. Static window coverings are fixed in place while dynamic window coverings can change their status manually or automatically. Dynamic window coverings can control daylight and solar energy entering the building. Dynamic window coverings are effective in adapting to changing outdoor and indoor conditions. Optimal control of window coverings can increase occupant comfort (visual and thermal comfort) while saving building energy use (lighting, cooling, and heating energy). [7] Typical dynamic window coverings include automated blinds and automatic shades.
Window blinds and shades can be controlled to avoid glare while introducing daylight to the building. The height of the blind and the angle of the slat can be determined by daylighting demand and solar positions (azimuth, altitude). By controlling the height of shades or blinds, the optimal amount of sunlight can be introduced to meet the target horizontal illuminance (work plane illuminance). The optimal angle of the blind slats can protect occupants from direct sunlight (cut-off angle strategy). Glare can also be controlled by glare index-based models, such as discomfort glare probability (DGP). [8]
Window coverings can be controlled to minimize overheating. When the sunlight is strong, fully closed window coverings can decrease the cooling load while maintaining occupants’ thermal comfort. When the outdoor temperature is extremely low, fully closed drapes or curtains can reduce the heating load. [9]
Control of window coverings can also be determined by occupants’ personal preferences. The occupant may prefer to close the window coverings due to privacy issues. Indoor conditions, such as furniture configuration or occupant position, may also affect the shade or blind control.
Dynamic window coverings are important in the area of building automation.
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.
Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight. Daylighting is sometimes used as the main source of light during daytime in buildings. This can save energy in place of using artificial lighting, which represents a major component of energy consumption in buildings. Proper lighting can enhance task performance, improve the appearance of an area, or have positive psychological effects on occupants.
A window blind is a type of window covering. There are many different kinds of window blinds which use a variety of control systems. A typical window blind is made up of several long horizontal or vertical slats of various types of hard material, including wood, plastic or metal which are held together by cords that run through the blind slats. Vertical blinds run along a track system which can tilt open and closed and move side-to-side. Window blinds can be manoeuvred with either a manual or remote control by rotating them from an open position, with slats spaced out, to a closed position where slats overlap and block out most of the light. There are also several types of window coverings, called shades, that use a single piece of soft material instead of slats.
Smart glass, also known as switchable glass, dynamic glass, and smart-tinting glass, is a type of glass that can change its optical properties, becoming opaque or tinted, in response to electrical or thermal signals. This can be used to prevent sunlight and heat from entering a building during hot days, improving energy efficiency. It can also be used to conveniently provide privacy or visibility to a room.
Building automation (BAS), also known as building management system (BMS) or building energy management system (BEMS), is the automatic centralized control of a building's HVAC, electrical, lighting, shading, access control, security systems, and other interrelated systems. Some objectives of building automation are improved occupant comfort, efficient operation of building systems, reduction in energy consumption, reduced operating and maintaining costs and increased security.
Building science is the science and technology-driven collection of knowledge in order to provide better indoor environmental quality (IEQ), energy-efficient built environments, and occupant comfort and satisfaction. Building physics, architectural science, and applied physics are terms used for the knowledge domain that overlaps with building science. In building science, the methods used in natural and hard sciences are widely applied, which may include controlled and quasi-experiments, randomized control, physical measurements, remote sensing, and simulations. On the other hand, methods from social and soft sciences, such as case study, interviews & focus group, observational method, surveys, and experience sampling, are also widely used in building science to understand occupant satisfaction, comfort, and experiences by acquiring qualitative data. One of the recent trends in building science is a combination of the two different methods. For instance, it is widely known that occupants' thermal sensation and comfort may vary depending on their sex, age, emotion, experiences, etc. even in the same indoor environment. Despite the advancement in data extraction and collection technology in building science, objective measurements alone can hardly represent occupants' state of mind such as comfort and preference. Therefore, researchers are trying to measure both physical contexts and understand human responses to figure out complex interrelationships.
Leadership in Energy and Environmental Design (LEED) is a green building certification program used worldwide. Developed by the non-profit U.S. Green Building Council (USGBC), it includes a set of rating systems for the design, construction, operation, and maintenance of green buildings, homes, and neighborhoods, which aims to help building owners and operators be environmentally responsible and use resources efficiently.
Thermal comfort is the condition of mind that expresses subjective satisfaction with the thermal environment. The human body can be viewed as a heat engine where food is the input energy. The human body will release excess heat into the environment, so the body can continue to operate. The heat transfer is proportional to temperature difference. In cold environments, the body loses more heat to the environment and in hot environments the body does not release enough heat. Both the hot and cold scenarios lead to discomfort. Maintaining this standard of thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC design engineers.
Glare is difficulty of seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Because of this, some cars include mirrors with automatic anti-glare functions and in buildings, blinds or louvers are often used to protect occupants. Glare is caused by a significant ratio of luminance between the task and the glare source. Factors such as the angle between the task and the glare source and eye adaptation have significant impacts on the experience of glare.
A light shelf is a horizontal surface that reflects daylight deep into a building. Light shelves are placed above eye-level and have high-reflectance upper surfaces, which reflect daylight onto the ceiling and deeper into the space.
Mixed-mode ventilation is a hybrid approach to space conditioning that uses a combination of natural ventilation from operable windows, and mechanical systems that include air distribution equipment and refrigeration equipment for cooling. A well-designed mixed-mode building begins with intelligent facade design to minimize cooling loads. It then integrates the use of air conditioning when and where it is necessary, with the use of natural ventilation whenever it is feasible or desirable, to maximize comfort while avoiding the significant energy use and operating costs of year-round air conditioning.
Daylight harvesting systems use daylight to offset the amount of electric lighting needed to properly light a space, in order to reduce energy consumption. This is accomplished using lighting control systems that are able to dim or switch electric lighting in response to changing daylight availability. The term Daylight Harvesting has become the standard in the fields of lighting, sustainable architecture, and active daylighting industries.
Sustainable refurbishment describes working on existing buildings to improve their environmental performance using sustainable methods and materials. A refurbishment or retrofit is defined as: "any work to a building over and above maintenance to change its capacity, function or performance' in other words, any intervention to adjust, reuse, or upgrade a building to suit new conditions or requirements". Refurbishment can be done to a part of a building, an entire building, or a campus. Sustainable refurbishment takes this a step further to modify the existing building to perform better in terms of its environmental impact and its occupants' environment.
Radiant heating and cooling is a category of HVAC technologies that exchange heat by both convection and radiation with the environments they are designed to heat or cool. There are many subcategories of radiant heating and cooling, including: "radiant ceiling panels", "embedded surface systems", "thermally active building systems", and infrared heaters. According to some definitions, a technology is only included in this category if radiation comprises more than 50% of its heat exchange with the environment; therefore technologies such as radiators and chilled beams are usually not considered radiant heating or cooling. Within this category, it is practical to distinguish between high temperature radiant heating, and radiant heating or cooling with more moderate source temperatures. This article mainly addresses radiant heating and cooling with moderate source temperatures, used to heat or cool indoor environments. Moderate temperature radiant heating and cooling is usually composed of relatively large surfaces that are internally heated or cooled using hydronic or electrical sources. For high temperature indoor or outdoor radiant heating, see: Infrared heater. For snow melt applications see: Snowmelt system.
In building engineering, a climate-adaptive building shell (CABS) is a facade 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.
Healthy building refers to an emerging area of interest that supports the physical, psychological, and social health and well-being of people in buildings and the built environment. Buildings can be key promoters of health and well-being since most people spend a majority of their time indoors. According to the National Human Activity Pattern Survey, Americans spend "an average of 87% of their time in enclosed buildings and about 6% of their time in enclosed vehicles."
The artificial sky is a daylight simulation device that replicates the light coming from the sky dome. An architectural scale model or 1:1 full-scaled aircraft is placed under an artificial sky to predict daylight penetration within buildings or aircraft that subjects to different situations, complex geometries, or heavily obstructed windows. The concept of the artificial sky was derived due to heliodon’s limitation in providing a stable lighting environment for evaluating the diffuse skylight component.
Occupant-centric building controls or Occupant-centric controls (OCC) is a control strategy for the indoor environment, that specifically focuses on meeting the current needs of building occupants while decreasing building energy consumption. OCC can be used to control lighting and appliances, but is most commonly used to control heating, ventilation, and air conditioning (HVAC). OCC use real-time data collected on indoor environmental conditions, occupant presence and occupant preferences as inputs to energy system control strategies. By responding to real-time inputs, OCC is able to flexibly provide the proper level of energy services, such as heating and cooling, when and where it is needed by occupants. Ensuring that building energy services are provided in the right quantity is intended to improve occupant comfort while providing these services only at the right time and in the right location is intended to reduce overall energy use.
Alan Kabanshi is an engineer, researcher and associate professor of energy systems at the University of Gävle, Sweden. His work focuses on resource efficient systems in built environments, specializing in energy systems, sustainable building systems, Heating Ventilation and Air Conditioning (HVAC), and cognitive psychology of climate change. He is currently serving as a co-Director for the research programme Urban Transition under the profile Urban Sustainability.
