Editing Daylighting (architecture) (section)

==LEED documentation==
The [[Leadership in Energy and Environmental Design|LEED]] 2009 daylighting standards were intended to connect building occupants with the outdoors through use of optimal daylighting techniques and technologies. According to these standards, the maximum value of 1 point can be achieved through four different approaches. The first approach is a computer simulation to demonstrate, in clear sky conditions, the daylight illuminance levels 108–5,400 lux on, September 21 between 9:00&nbsp;a.m. and 3:00&nbsp;p.m. Another prescriptive approach is a method that uses two types of side-lighting, and three types of top-lighting to determine if a minimum of 75% daylighting is achieved in the occupied spaces. A third approach uses indoor light measurements showing that between 108 and 5,400 lux have been achieved in the space. The last approach is a combination of the other three calculation methods to prove that the daylight illumination requirements are achieved.<ref>{{cite web |title=Daylight and views - daylight |url=http://www.usgbc.org/node/1732577?return=/credits/healthcare/v2009 |website=U.S. Green Building Council |access-date=10 December 2014}}</ref>

The LEED 2009 documentation is based upon the [[daylight factor]] calculation. The daylight factor calculation is based on uniform overcast skies. It is most applicable in [[Northern Europe]] and parts of [[North America]].<ref name="IESNA">{{cite book |last=Rea |first=Mark |date=July 2000 |title=IESNA Lighting Handbook |edition=9th |publisher=Illuminating Engineering |isbn=978-0879951504 |url-access=registration |url=https://archive.org/details/iesnalightinghan00ream }}</ref> Daylight factor is "the ratio of the illuminance at a point on a plane, generally the horizontal work plane, produced by the luminous flux received directly or indirectly at that point from a sky whose luminance distribution is known, to the illuminance on a horizontal plane produced by an unobstructed hemisphere of this same sky."<ref name="IESNA" />

LEED v4 daylighting standards are the most current as of 2014. The new standards are similar to the old standards, but also intend to "reinforce circadian rhythms, and reduce the use of electrical lighting by introducing daylight in the space.<ref name="USGBCV4">{{cite web |title=Daylight |url=http://www.usgbc.org/node/2614120?return=/credits/healthcare/v4 |publisher=USGBC |website=U.S. Green Building Council |access-date=10 December 2014}}</ref> Two options exist for achieving the maximum value of these two most recent points. One option is to use a computer simulation to demonstrate that a spatial daylight autonomy of 300 lux for at least 50% of the time, and an annual sunlight exposure of 1,000 lux for 250 occupied hours per year, exists in the space. Another option is to show that illuminance levels are between 300 lux and 3,000 lux between 9:00&nbsp;a.m. and 3:00&nbsp;p.m. on a clear day at the equinox for 75% or 90% of the floor area in the space.<ref name="USGBCV4" /> The overall goal of the LEED v4 daylighting metrics is to analyze both the quantity and quality of the light, as well as to balance the use of glazing to ensure more light and less cooling load.