Daylighting Resources – Healthy K12

Build your understanding of daylighting, factors, a more in-depth explanation of standards, and strategies to improve your high-performance learning environment.

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Glossary Terms

Color Rendering Index (CRI)	Color Rendering Index (CRI) measures the color of objects illuminated by a lamp compared to objects illuminated by a reference lamp of the same color temperature.
Color Temperature	Color temperature, measured in units Kelvin, estimates the color distribution a light source emits. The higher the color temperature, the bluer the light.
Daylight	Daylight is the volume of natural light that enters a building between sunrise and sunset.
Daylighting	Daylighting is the controlled admission of natural light into a building to create a visually stimulating and productive environment for building occupants, reduce electric lighting, and save energy. More importantly, daylighting is an essential environmental feature for creating a healthy learning space by triggering a hormonal response in people.
Direct Sunlight	Daylight received directly from the sun.
Diffuse Skylight	All skylight and diffuse-reflected sunlight.
Glare	It shows us areas of high brightness right next to areas of low brightness cause glare, making people uncomfortable.
Illuminance	Illuminance or light levels refer to the magnitude of light per unit area in a room.
Non-visible Light
Visible Light
Controls
Age Appropriate
Balance

Key Factors

Temporality

Uniformity

Controls

Age Appropriate

Balance

Factors for Achieving Good Lighting Performance

Windows	The number, size, and placement of windows in your child’s classroom could determine their class participation and ability to sleep that night. If possible, in the design of a new school, place fewer but larger glazing apertures to improve the amount of daylight admission into a classroom. In addition to windows, a classroom may also use provide other aperatures like skylights.
Location	The geographical location considers climate and seasonality.
Shading Devices	A classroom design may feature exterior horizontal window overhangs and vertical fins that project beyond the window, minimize solar heat gain and lower excessive illumination levels onto desk surfaces.
Glazing Construction Materials	The glazing materials can feature films that reduce solar heat gain and lower the amount of visible light in the classroom.
Interior Space Configruation	The location of moveable partitions and furniture in the classroom improves the helpful daylight illuminance in the school.
Materials	The construction materials of the furniture, walls, floors, and ceilings reflect light in different ways. The classroom can feature interior finishes that balance the distribution of daylight in the classroom.
Daylight Sensors	Daylight sensors control the lighting system's responsiveness to respond to the dynamic changes in daylight in the classroom.
Occupant Sensors	Occupant sensors automatically turn on and turn off the lighting in a classroom to provide security and energy savings.
Operations	The hours that the school doors open and close in the fall, winter, spring, and summer significantly impact the energy usage for lighting loads necessary for teachers and students in a classroom.

Standards and Metric

Illuminance	Illuminance is a daylight metric that shows us high brightness areas right next to low brightness cause glare, making people uncomfortable.
Daylight Factor (DF)	The daylight factor is the most dominant daylight metric used today due to its simplicity. The daylight factor is the ratio of the light level inside a building to outdoors during an overcast sky condition.
Daylight Autonomy (DA)	Daylight autonomy is the percentage of the operating period (or the number of hours) that a particular daylight level is exceeded throughout the year.
Useful Daylight Illuminance (UDI)	UDI is a location-based dynamic daylight metric that uses actual weather data to produce hourly annual results. UDI measures daylight lux levels deemed 'useful' for occupancy use.
Spatial Daylight Autonomy (sDA)	Spatial daylight autonomy is a dynamic daylight metric that measures the amount of space that receives sufficient daylight. More specifically, it examines the percentage of area that receives 300 lux for at least 50% of the total operational hours measured at working plane ⁵. What sets sDA apart from other dynamic daylight metrics is the incorporation of window blinds. These blinds are set to close and open depending on the amount of direct sunlight the space receives.
Annual Sunlight Exposure (ASE)	Annual sunlight exposure is a dynamic daylight metric that measures the amount of space that receives too much daylight.
Daylight Glare Probability (DGP)	Daylight glare probability quantifies occupants' perceived Glare from daylight at a point-in-time, position in space, and occupant view angle. It is calculated by evaluating the entire visual field of a potential occupant, taking into account the light intensity, size of the glare source, contrast, and position in the field of view. Expressed from 0 to 1, it ranges from Imperceptible Glare (0.45).
Spatial Daylight Autonomy (sDA), 300lux/50%	We assess the design for daylight autonomy to understand the light quality in regularly occupied spaces at a point in space. Spatial Daylight Autonomy sDA 300, 50% provides the daylight illuminance for a given area to report the portion of floor area that exceeds 300 lux for a percentage of time such as 50% of the annual occupied hours.
Annual Sunlight Exposure (ASE), 1000, 250	We assess the design for illuminance levels above 3000 lux to understand the light quality in regularly occupied spaces at a point in space. Annual Sun Exposure requires that the project design maintain 10% of the floor area with more than 1,000 lux and less than 250 hours under the ASE requirement.
LEED Version 4.1 for Schools	LEED Version 4.1 for Schools requires an analysis for sDA where An average value of at least 55% (2 pts), 75% (3 pts), 40% (1 pt) for the regularly occupied floor area. In addition, an analysis for ASE requires no more than 10% of the area can receive more than 1,000 lux (93 fc) for 250 hours each year.
Well Building Standard V3 for Schools	Similarly, the Well Building Standard requires an analysis for sDA where an average value of at least 55% at least 55% for regularly occupied space; ASE with no more than 10% of the area can receive more than 1,000 lux (93 fc) for 250 hours each year; and illuminance with an average of 175 lux (16 fc) or more measured on the horizontal plane 0.76 m (30 inches) above the finished floor.
U.S. California Title 24, 2019 Building Energy Efficiency Standards	Title 24 requires a daylit zone of 75% of the floor area within the primary side-lit daylit zone or skylit daylit zone.
U.S. Collaborative for High-Performance Schools (CHPS)	CHPS requires daylight excess, an annual daylight autonomy analysis with the Illuminance target multiplier of 10x (i.e., a 30fc classroom target would use 300fc for Daylight Excess). School performance also requires a spatial daylight saturation (sDS) where it is greater than 50 to 90% sDS 300/50%.
U.K. Education Funding Agency (EFA)	EFA requires an useful daylight illuminance analysis with an average of 80% UDI-a (100 to 3,000 lux). Additionally, there are criteria for daylight autonomy (DA) with a minimum of 50% of the time for 50% of the working plane, with a target illuminance of 300 lux.
U.K. Building Research Establishment Environmental Assessment Methodology (BREEAM)	BREEAM requires the following daylight analysis and evaluation: Daylight Factor (DF) with an average of 1.5 to 2.25 (depending on latitude) for 60 to 80% area; Daylighting uniformity with a ratio of at least 0.3, at least 80% of the room has a view of the sky from desk or tabletop height, and room depth criteria to be satisfied; and daylight illuminance for average and minimum where a ratio of at least 0.3, at least 80% of the room has a view of the sky from desk or tabletop height, and room depth criteria to be satisfied.

References

School Design	Tanner, C.K. (2009), "Effects of school design on student outcomes", Journal of Educational Administration, Vol. 47 No. 3, pp. 381-399.
Circadian Light	Stephanie J Crowley, Sean W Cain, Angus C Burns, Christine Acebo, Mary A Carskadon (2015), "Increased Sensitivity of the Circadian System to Light in Early/Mid-Puberty", J Clin Endocrinol Metab.100(11):4067-73.
Physical Activity	Daniel Aggio, et.al. (2015). "Association of Light Exposure on Physical Activity and Sedentary Time in Young People", Int J Environ Res Public Health. 12(3): 2941–2949.
Performance	Mariana G. Figueiro, Mark S. Rea, "Short-Wavelength Light Enhances Cortisol Awakening Response in Sleep-Restricted Adolescents", International Journal of Endocrinology, vol. 2012, Article ID 301935, 7 pages, 2012.
Classroom Lighting	Oliver Keis, Hannah Helbig, Judith Streb, Katrin Hille (2014), "Influence of blue-enriched classroom lighting on students׳ cognitive performance", Trends in Neuroscience and Education, Volume 3, Issues 3–4, pp. 86-92.
Visual Comfort	Shamsul, B., Sia, C. , Ng, Y. , & Karmegan, K. (2013). Effects of Light's Colour Temperatures on Visual Comfort Level, Task Performances, and Alertness among Students. American Journal of Public Health Research, 1(7), 159-165.
Student Learning	Michael Mott, et.al. (2012), "Illuminating the Effects of Dynamic Lighting on Student Learning", SAGE Open 2(2), pp.1-9.
Impact on Reading Fluency Scores	Mott, M.S., Robinson, D.H., Williams-Black, T.H. et al. The supporting effects of high luminous conditions on grade 3 oral reading fluency scores. SpringerPlus 3, 53 (2014).