Editing Daylighting (architecture) (section)

==Types==
'''Passive daylighting''' is a system of both collecting [[sunlight]] using static, non-moving, and non-tracking systems (such as windows, [[sliding glass door]]s, most [[skylight]]s, [[light tube]]s) and reflecting the collected [[daylight]] deeper inside with elements such as [[light shelves]]. Passive daylighting systems are different from '''active daylighting''' systems in that active systems track and/or follow the sun, and rely on mechanical mechanisms to do so.

===Windows===
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{{Main|Window}}

Windows are the most common way to admit daylight into a space. Their vertical orientation means that they selectively admit sunlight and diffuse daylight at different times of the day and year. Therefore, windows on multiple orientations must usually be combined to produce the right mix of light for the building, depending on the climate and latitude. There are three ways to improve the amount of light available from a window:<ref name="Building for Energy Independence: Sun/Earth Buffering and Superinsulation">{{cite book |date= 1983 |title= Building for Energy Independence: Sun/Earth Buffering and Superinsulation |publisher= Community Builders |isbn= 978-0960442249 |url-access= registration |url= https://archive.org/details/buildingforenerg0000boot }}</ref> (a) placing the window close to a light colored wall, (b) slanting the sides of window openings so the inner opening is larger than the outer opening, or (c) using a large light colored window-sill to project light into the room. Besides permitting daylighting into the building, windows serve another function in daylighting practice, providing views out.<ref>{{cite journal |last1= Kent |first1= Michael |last2= Schiavon |first2= Stefano |date= 2020 |title= Evaluation of the effect of landscape distance seen in window views on visual satisfaction | url= https://escholarship.org/content/qt6gd9t8pj/qt6gd9t8pj.pdf?t=qf0euu |journal= Building and Environment | volume= 183 |  pages= 107160 | doi= 10.1016/j.buildenv.2020.107160 |bibcode= 2020BuEnv.18307160K |s2cid= 221935768 | access-date= 2021-08-11}}</ref> To enhance the quality of the view seen from a window, three primary variables need to be ensure: view content (what can be seen in the view), view access (how much of the window view can be seen), and view clarity (how clearly the view can be seen).<ref>{{cite journal |last1= Ko |first1= Won Hee |last2= Kent|first2= Michael | last3= Schiavon | first3= Stefano | last4= Levitt | first4= Brendon | last5= Betti | first5= Giovanni | date= 2021 |title= A Window View Quality Assessment Framework | url= https://www.tandfonline.com/doi/full/10.1080/15502724.2021.1965889?scroll=top&needAccess=true |journal= LEUKOS |volume= 18 |issue= 3 |pages= 268–293 | doi= 10.1080/15502724.2021.1965889 |arxiv= 2010.07025 |s2cid= 222341349 | access-date= 2021-11-30}}</ref> View clarity is often influenced by the amount of shading provided by blinds or devices used to protect occupants from harsh daylight (e.g. [[Glare (vision)|glare]]) or for reasons of [[visual privacy]]. Environmental criteria serve as important criteria to gauge the quality of window view content.<ref>{{cite journal |last1= Kent |first1= Michael |last2= Schiavon|first2= Stefano | date= 2022 |title= Predicting Window View Preferences Using the Environmental Information Criteria | url= https://escholarship.org/content/qt7rv6936v/qt7rv6936v.pdf?t=rgtbft |journal= LEUKOS |volume= 19 |issue= 2 |pages= 190–209 | doi=10.1080/15502724.2022.2077753 |s2cid= 251121476 | access-date= 2022-11-09}}</ref> These criteria can be distilled into five important factors, namely: Location, time, weather, people, and nature. Notably, views that are able to provide building inhabitants with content of [[nature]] far outweigh the other four Environmental Information Criteria.

Different types and grades of [[glass]] and different window treatments can also affect the amount of light transmission through the windows. The type of [[Glazing (window)|glazing]] is an important issue, expressed by its VT coefficient (Visual Transmittance),<ref>{{cite web|url = http://www.nfrc.org/energy-performance-label/|title = Energy Performance Label|website = The National Fenestration Rating Council|date = 20 July 2016|access-date = 4 March 2019}}</ref> also known as visual light transmittance (VLT). As the name suggests, this coefficient measures how much visible light is admitted by the window. A low VT (below 0.4) can reduce by half or more the light coming into a room. But be also aware of high VT glass: high VT numbers (say, above 0.60) can be a cause of glare. On the other hand, you should also take into account the undesirable effects of large windows.

Windows grade into translucent walls (below).

====Clerestory windows====
Another important element in creating daylighting is the use of [[clerestory]] windows. These are high, vertically placed windows. They can be used to increase direct solar gain when oriented towards the equator. When facing toward the sun, clerestories and other windows may admit unacceptable [[Glare (vision)|glare]]. In the case of a [[passive solar]] house, clerestories may provide a direct light path to polar-side (north in the northern hemisphere; south in the southern hemisphere) rooms that otherwise would not be illuminated. Alternatively, clerestories can be used to admit diffuse daylight (from the north in the northern hemisphere) that evenly illuminates a space such as a classroom or office.

Often, clerestory windows also shine onto interior wall surfaces painted white or another light color. These walls are placed so as to reflect indirect light to interior areas where it is needed. This method has the advantage of reducing the directionality of light to make it softer and more diffuse, reducing shadows.

====Sawtooth roof====
Another roof-angled glass alternative is a [[saw-tooth roof|sawtooth roof]] (found on older factories). Sawtooth roofs have vertical roof glass facing away from the equator side of the building to capture diffused light (not harsh direct equator-side solar gain).<ref name="LG10">{{cite book |date=1999|title= CIBSE Lighting Guide 10: Daylighting and window design |publisher= CIBSE |isbn= 978-0-900953-98-9}}</ref> 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 "solar furnace" skylight problem, but still allows warm interior air to rise and touch the exterior roof glass in the cold winter, with significant undesirable heat transfer.<ref>{{cite journal | first = F. | last = Asdrubali | year = 2003 | title = Lighting Research and Technology: "Daylighting performance of sawtooth roofs of industrial buildings "| journal=Lighting Research and Technology | volume = 35 | issue = 4| pages = 343–359 | doi = 10.1191/1365782803li094oa| s2cid = 109902823 }}</ref>

===Skylights===
{{Main|Skylight}}
[[File:Skylight w cuppola.jpg|thumb|right|Modern [[skylight]]]]

A skylight or rooflight is a light-permitting structure or window, usually of transparent or translucent glass, that forms part (or all) of the roof area of a building for daylighting or ventilation.

===Laylights===

[[File:Skylights at Lyme Art Association.jpg|thumb|right|Skylights above [[Daylighting (architecture)#Laylights|laylights]] at the Lyme Art Association Gallery]]As an element of [[architecture]], a laylight is a [[Glazing (window)|glazed]] panel usually set flush with the [[ceiling]] for the purpose of admitting natural or artificial light.<ref>{{Cite web|url=https://www.merriam-webster.com/dictionary/laylight|title=Definition of LAYLIGHT}}</ref> Laylights typically utilize stained glass or lenses in their glazing, but can also use alternative materials.<ref>{{Cite web|url=https://www.athleticbusiness.com/rec-center/single-laylight-combines-natural-artificial-light-in-seating-area.html|title=Single Laylight Combines Natural, Artificial Light in Seating Area|date=9 June 2016}}</ref><ref>{{Cite web|url=https://www.johnjermain.org/2012/03/30/librarys-historic-laylight-removed-for-restoration/|title=Library's Historic Laylight Removed for Restoration|date=30 March 2012|access-date=19 October 2021|archive-date=23 October 2022|archive-url=https://web.archive.org/web/20221023165020/https://www.johnjermain.org/2012/03/30/librarys-historic-laylight-removed-for-restoration/|url-status=dead}}</ref> For example, the [[Lyme Art Association|Lyme Art Association Gallery]] utilizes translucent white [[muslin]] laylights below its skylights.<ref>{{cite journal|title=A Museum owned by Artists|journal=Museum Work: Including the Proceedings of the American Association of Museums|date=1921|volume=4|issue=1|pages=47|url=https://books.google.com/books?id=dn5PAQAAMAAJ&q=lyme+gallery+charles+a+platt&pg=RA1-PA47|publisher=American Association of Museums}}</ref> A laylight differs from a glazed (or closed) [[skylight]] in that a skylight functions as a roof [[window]] or aperture, while a laylight is flush with the ceiling of an interior space.<ref>{{Cite web|url=https://bmroofers.co.uk/difference-between-skylights-veluxes-and-roof-windows/|title=What is the Difference Between Skylights, Veluxes, and Roof Windows? &#124; Information Blog Post &#124; First Class Roofing Service|access-date=2021-10-19|archive-date=2022-10-23|archive-url=https://web.archive.org/web/20221023165017/https://bmroofers.co.uk/difference-between-skylights-veluxes-and-roof-windows/|url-status=dead}}</ref><ref>{{Cite web|url=https://northeasttimes.com/2015/12/02/the-future-is-bright/|title = The future is bright|date = 3 December 2015}}</ref> When paired with a [[roof lantern]] or skylight on a sloped roof, a laylight functions as an interior light diffuser.<ref>{{Cite web|url=https://www.wbdg.org/guides-specifications/building-envelope-design-guide/fenestration-systems/sloped-glazing |title=Sloped Glazing |work=WBDG - Whole Building Design Guide }}</ref> Before the advent of electric lighting, laylights allowed transmission of light between floors in larger buildings, and were not always paired with skylights.<ref>{{cite news |url=https://www.washingtonpost.com/local/answer-man-sheds-some-light-on-curious-glass-panels-at-the-us-capitol/2017/03/25/1b06f2f0-0fee-11e7-9b0d-d27c98455440_story.html |title=Answer Man sheds some light on curious glass panels at the U.S. Capitol |date=25 March 2017 |newspaper=[[The Washington Post]]}}</ref>

===Atrium===
{{main|Atrium (architecture)}}
An atrium is a large open space located within a building. It is often used to light a central circulation or public area by daylight admitted through a glass roof or wall. Atria provide some daylight to adjacent working areas, but the amount is often small and does not penetrate very far.<ref name="The SLL Lighting Handbook">{{cite book |title=The SLL Lighting Handbook |publisher=Chartered Institution of Building Services Engineers; 1st edition |date=2009 |isbn=9781906846022}}</ref> The main function of an [[atrium (architecture)|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.<ref name=" Daylighting in atrium buildings">{{cite book |last1=Littlefair |first1=P.J. |last2=Aizlewood |first2=M.E. |title=Daylighting in atrium buildings |publisher=BRE Information Paper IP3/98 |date=1998 |isbn=9781860811944}}</ref> Light from the sky can easily penetrate the upper storeys but not the lower, which rely primarily on light reflected from internal surfaces of the atrium such as floor-reflected light.<ref>{{cite journal |last=Sharples |first=S. |title=Reflectance distributions and atrium daylight levels: a model study |journal=Lighting Research and Technology |volume=31 |issue=4 |pages=165–170 |year=1999 |s2cid=110668116 |doi=10.1177/096032719903100405}}</ref> The upper stories need less window area than the lower ones, and if the atrium walls are light in color the upper walls will reflect light toward the lower stories.<ref name="LG10"/>

===Translucent walls===
[[File:Glass block wall on the campus of the University of Texas-El Paso LCCN2014631180.tif|thumb|Glass brick wall, outdoors]]
[[File:House of Arts in Gödöllő. Glass bricks.JPG|thumb|Glass brick wall, indoors]]
[[File:Interior Jacobsen House Bathroom Earthship 2009.JPG|thumb|Bottle wall]]
Walls made of [[glass brick]] are translucent-to-transparent. Traditionally they are hollow and [[grout]]ed with a fine concrete grout, but some modern glass brick walls are solid cast glass<ref>{{cite web|url=https://archpaper.com/2016/04/mvrdv-integrates-terra-cotta-brick-and-glass-for-a-facade-in-amsterdam/|title=MVRDV integrates terra-cotta brick and glass for a facade in Amsterdam |website=archpaper.com |access-date=2017-11-06|date=2016-04-21}}</ref> grouted with a transparent glue.<ref>{{cite news|url=https://www.dezeen.com/2016/04/20/crystal-houses-amsterdam-chanel-store-mvrdv-glass-facade-technology/|title=MVRDV replaces traditional facade with glass bricks that are stronger than concrete|date=2016-04-20|work=Dezeen|access-date=2017-11-06}}</ref><ref>{{cite news |url=https://inhabitat.com/glass-bricks-stronger-than-concrete-clad-chanels-crystal-houses/|title=Glass bricks "stronger than concrete" clad Amsterdam's Crystal Houses|access-date=2017-11-06 }}</ref> If the glue matches the [[refractive index]] of the glass, the wall can be fairly transparent.

Increasing the amount of concrete, bottle walls embed bottles that run right through the wall, transmitting light. Concrete walls with glass prisms running through them have also been made. With the advent of cheaper [[optical fiber]]s and [[translucent concrete|fiber-optic concrete]] walls, daylight (and shadow images) can then pass directly through a solid concrete wall, making it translucent; fiber optics will lead light around bends and over tens of meters.<ref>{{cite web|url=https://www.tfod.in/art-design-articles/22/see-through-concrete-litracon|title=See-through concrete: LiTracon|date=14 November 2014|website=The Future of Design}}</ref> Typically only a few percent of the light is transmitted (the percent transmittance is about half the percent of the surface that is fibers, and usually only ~5% fibers are used).<ref>{{cite journal|url=http://www.ijsrp.org/research-paper-1013/ijsrp-p2283.pdf|journal= International Journal of Scientific and Research Publications|volume=3|date=October 2013|issn=2250-3153|title=TRANSLUCENT CONCRETE|author1=SOUMYAJIT PAUL|author2=AVIK DUTTA}}</ref><ref>{{cite web|url=http://sinberbest.berkeley.edu/sites/default/files/Anilodic%2BDaylight%2BConcentrator%2Bof%2BStructural%2BTranslucent%2BConcrete%2BEnvelope_%2BBaofeng%2BHuang.pdf|title=Anidolic Daylight Concentrator of Structural Translucent Concrete Envelope|website=Sinberbest.berkeley.edu|access-date=4 August 2018}}</ref>

Both glass and concrete conduct heat fairly well, when solid, so none of these walls [[insulation value|insulate well]]. They are therefore often used outdoors, as a divider between two heated spaces (see images), or in very [[temperate climates]].

[[Greenhouse]] walls (and roofs) are made to transmit as much light and as little heat as possible. They use a variety of materials, and may be transparent or translucent.

===Remote distribution===
{{main|Anidolic lighting}}
It is possible to provide some daylight into spaces that have low possibility of windows or skylights through remote distribution devices such as mirrors, [[Prism (optics)|prisms]], or [[light tube]]s. This is called [[anidolic lighting]], from [[nonimaging optics|anidolic (non-image-forming) optics]]. The non-linear response of the human eye to light means that spreading light to a broader area of a room makes the room appear brighter, and makes more of it usefully lit.

Remote daylight distribution systems have losses, and the further they have to transmit the daylight and the more convoluted the path, the greater the inefficiency.<ref>{{cite journal |last=Littlefair |first=P.J. |year=1990 |title=Review Paper: Innovative daylighting: Review of systems and evaluation methods |journal=Lighting Research and Technology |volume=22 |pages=1–17 |doi=10.1177/096032719002200101 |s2cid=108501995}}<!--|access-date=November 17, 2015--></ref> The efficiency of many remote distribution systems can also vary dramatically from clear to overcast skies. Nonetheless, where there is no other possibility of providing daylight to a space, remote distribution systems can be appreciated.<ref name="The SLL Lighting Handbook"/>

====Light reflectors and shelves====
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{{see also|Architectural light shelf}}
Once used extensively in office buildings, the manually adjustable light reflector is seldom in use today having been supplanted by a combination of other methods in concert with artificial illumination. The reflector had found favor where the choices of artificial light provided poor illumination compared to modern electric lighting.

Light shelves are an effective way to enhance the lighting from windows on the equator-facing side of a structure, this effect being obtained by placing a white or reflective metal light shelf outside the window.<ref name="The SLL Lighting Handbook"/> Usually the window will be protected from direct summer season 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.<ref>{{cite journal |last=Littlefair |first=P.J. |title=Light shelves: Computer assessment of daylighting |journal=Lighting Research and Technology |volume=27 |issue=2 |pages=79–91 |year=1995 |s2cid=111215708 |doi=10.1177/14771535950270020201}}</ref>

In the cold winter, a natural light shelf is created when there is [[snow]] on the ground which makes it reflective. Low winter sun (see [[Sun path]]) 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. Glare control (drapes) may be required.

====Prisms====
{{main|Prism lighting}}
[[File:Daylight Redirecting Film.jpg|thumb|Daylight redirecting film bending light upwards]]

The oldest use of prisms for daylighting may well be [[deck prism]]s, let into the decks of ships to transmit light below. Later, [[pavement light]]s or [[vault light]]s were used to light basement areas under sidewalks.<ref name="glassian">{{cite web|url=http://www.glassian.org/Prism/|title=Prism Glass {{!}} glassian|website=Glassian.org |access-date=2017-11-06}}</ref>

Prisms that used [[total internal reflection]] to throw light sideways, lighting the deeper portions of a room, later became popular. Early thick, slow-cooling cast glass prism tiles were often known as "luxfer tiles" after a major manufacturer.<ref name=glassian/> They were and are used in the upper portions of windows, and some believe that they contributed to the trend from dark, subdivided Victorian interiors to open-plan, light-coloured ones.{{citation needed|date=September 2017}}

[[Daylight redirecting window film]] (DRF) is a thin plastic version of the old glass prism tiles. It can be used as a substitute for opaque blinds.<ref>{{cite web|url=https://www.serdp-estcp.org/Program-Areas/Energy-and-Water/Energy/Conservation-and-Efficiency/EW-201014|title=EW-201014 Fact Sheet|last=Noblis|website=Serdp-Estcp.org |access-date=2017-11-06}}</ref>

====Light tubes====
{{Main|Light tube}}
[[File:Solatube 160 DS rafter cutaway.jpg|thumb|Tubular daylighting devices harvest sunlight and transmit it through a highly reflective tube into an interior space at the ceiling level]]
[[File:Sonnenrohr.svg|thumb|Diagram of a [[light tube]]]]

Another type of device used is the light tube, also called a tubular daylighting device (TDD), which is placed into a roof and admits light to a focused 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.

TDDs 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 fiber optic bundle. It is frequently capped with a transparent, roof-mounted dome "light collector" and terminated with a diffuser assembly that admits the daylight into interior spaces and distributes the available light energy evenly (or else efficiently if the use of the lit space is reasonably fixed, and the user desired one or more "bright-spots").

The tubular daylighting device was invented by [[Solatube|Solatube International]] in 1986 and brought to market first in Australia in 1991.{{dubious|date=October 2017}}

===Active daylighting===
'''Active daylighting''' is a system of collecting sunlight using a mechanical device to increase the efficiency of light collection for a given lighting purpose. Active daylighting systems are different from passive daylighting systems in that passive systems are stationary and do not actively follow or track the sun.<ref>[http://www.tpub.com/content/UFC2/ufc_3_530_01/ufc_3_530_010046.htm Active Daylighting] {{webarchive |url=https://web.archive.org/web/20100202004451/http://www.tpub.com/content/UFC2/ufc_3_530_01/ufc_3_530_010046.htm |date=February 2, 2010}} retrieved 9 February 2009</ref> There are two types of active daylighting control systems: '''closed loop''' [[solar tracker|solar tracking]], and '''open loop''' solar tracking systems.
* '''Closed loop''' systems track the sun by relying on a set of [[lens (optics)|lens]] or sensors with a limited field of view, directed at the sun, and are fully illuminated by sunlight at all times.  As the sun moves, it begins to shade one or more sensors, which the system detect and activates motors or actuators to move the device back into a position where all sensors are once again equally illuminated.<ref name="inspira">{{Cite web |url=http://www.inspira.es/newsroom/981130.html |title=A new strategy for EUCLIDES subdegree solar tracking |access-date=2020-09-12 |archive-date=2010-04-06 |archive-url=https://web.archive.org/web/20100406130743/http://www.inspira.es/newsroom/981130.html |url-status=dead }}</ref>
* '''Open loop''' systems track the sun without physically following the sun via sensors (although sensors may be used for calibration).  These systems typically employ electronic logic which controls device motors or actuators to follow the sun based on a mathematical formula.  This formula is typically a pre-programmed sun path chart, detailing where the sun will be at a given latitude and at a given date and time for each day.