Editing Daylighting (architecture) (section)

==Daylighting metrics and analyses==
Daylight autonomy is the percentage of time that daylight levels are above a specified target [[illuminance]] within a physical space or building.<ref name="Reinhart"/> The calculation is based on annual data and the predetermined lighting levels. The goal of the calculation is to determine how long an individual can work in a space without requiring electrical lighting, while also providing optimal visual and physical comfort.<ref name="Reinhart">{{cite journal |last1=Reinhart |first1=Christoph |last2=Mardaljevic |first2=John  |last3=Rogers |first3=Zach |name-list-style=amp |date=2006 |title=Dynamic Daylight Performance Metrics for Sustainable Building Design |url=http://isites.harvard.edu/fs/docs/icb.topic256760.files/DynamicDaylightPerformanceMetricsInLeukos.pdf |journal=Leukos |volume=3 |issue=1 |pages=7–31 |doi=10.1582/LEUKOS.2006.03.01.001 |s2cid=18653435 |access-date=December 11, 2014}}</ref>

Daylight autonomy is beneficial when determining how daylight enters and illuminates a space. The drawback, however, is that there is no upper limit on [[luminance]] levels. Therefore, a space with a high internal heat gain deemed uncomfortable by occupants, would still perform well in the analysis. Achieving daylight autonomy requires an [[integrated design]] approach that guides the building form, siting, climate considerations, building components, lighting controls, and lighting design criteria.

===Continuous===
Continuous daylight autonomy, is similar to daylight autonomy but partial credit is attributed to time steps when the daylight illuminance lies below the minimum illuminance level.<ref name="ReferenceA">{{cite journal |last1= Jakubiec |first1=J.A. |last2=Reinhart |first2=C.F. |year=2012 |title=The 'adaptive zone' – A concept for assessing discomfort glare throughout daylit spaces |journal=Lighting Research and Technology |volume=44 |issue=2 |pages=149–170|doi=10.1177/1477153511420097 |s2cid=110072060 }}</ref> For example, if the target illuminance is 400 [[lux]] and the calculated value is 200 lux, daylight autonomy would give zero credit, while continuous daylight autonomy would give 0.5 credit (200/400=0.5). The benefit of continuous daylight autonomy is that it does not give a hard threshold of acceptable illuminance. Instead, it addresses the transition area—allowing for realistic preferences within any given space. For example, office occupants usually prefer to work at daylight below the illuminance threshold since this level avoids potential [[glare (vision)|glare]] and excessive contrast.<ref name="ReferenceA"/>

===Useful illuminance===
Useful daylight illuminance focuses on the direct sunlight that falls into a space. The useful daylight illuminance calculation is based on three factors—the percentage of time a point is below, between, or above an illuminance value. The range for these factors is typically 100–2,000 lux. Useful daylight illuminance is similar to daylight autonomy but has the added benefit of addressing glare and thermal discomfort.<ref>{{cite journal |last1=Nabil |first1=Azza |last2=Mardaljevic |first2=John |year=2006 |title=Useful daylight illuminances: A replacement for daylight factors |journal=Energy and Buildings |volume=38 |issue=7 |pages=1858–1866 |doi=10.1016/j.enbuild.2006.03.013 |bibcode=2006EneBu..38..905N }}<!--|access-date=December 10, 2014--></ref> The upper threshold is used to determine when glare or thermal discomfort is occurring and may need resolution.

===Illuminance distribution===
Besides determining how much illuminance is received on a horizontal surface, a method that analyses annual illuminance distributions for daylight has been developed.<ref>{{cite journal |last1=Kent |first1=Michael |last2=Schiavon |first2=Stefano |last3= Jakubiec |first3=Alstan |year=2020 |title=A dimensionality reduction method to select the most representative daylight illuminance distributions |journal=Journal of Building Performance Simulation |volume=13 |issue=1 |pages=122–135 |doi=10.1080/19401493.2019.1711456 |s2cid=211093664 |url=https://escholarship.org/uc/item/04x6v86j }}<!--|access-date=November 08, 2021--></ref> Every annual illuminance distribution is compared against each other using [[principal components analysis]]. This compares the relationship between each pattern. Daylight patterns that are more similar to each other due to architectural features and the time of the year the illuminance are produced are grouped together. Groups are used to form the most representative patterns for that given building. This method can be used to easily interpret how daylight is spread across the space throughout the entire year in any building.