To connect building occupants with the outdoors, reinforce circadian rhythms, and reduce the use of electrical lighting by introducing daylight into the space.
Provide manual or automatic (with manual override) glare-control devices for all regularly occupied spaces. Select one of the following three options.
Option 1. Simulation: Spatial Daylight Autonomy (2–3 points)Demonstrate through annual computer simulations that spatial daylight autonomy300/50% (sDA300/50%) of at least 55%, 75%, or 90% is achieved. Use regularly occupied floor area. Points are awarded according to Table 1.
Table 1. Points for daylit floor area: Spatial daylight autonomyAND
Demonstrate through annual computer simulations that annual sunlight exposure1000,250 (ASE1000,250) of no more than 10% is achieved. Use the regularly occupied floor area that is daylit per the sDA300/50% simulations. The sDA and ASE calculation grids should be no more than 2 feet (60 cm) square and laid out across the regularly occupied area at a work plane height of 30 inches (760 mm) above finished floor (unless otherwise defined). Use an hourly time-step analysis based on typical meteorological year data, or an equivalent, for the nearest available weather station. Include any permanent interior obstructions and movable furniture and partitions.
Option 2. Simulation: Illuminance Calculations (1–2 points)Demonstrate through computer modeling that illuminance levels will be between 300 lux and 3,000 lux for 9 a.m. and 3 p.m., both on a clear-sky day at the equinox, for the floor area indicated in Table 2. Use regularly occupied floor area.
Table 2. Points for daylit floor area: Illuminance calculationCalculate illuminance intensity for sun (direct component) and sky (diffuse component) for clear-sky conditions as follows:
- Use typical meteorological year data, or an equivalent, for the nearest available weather station.
- Select one day within 15 days of September 21 and one day within 15 days of March 21 that represent the clearest sky condition.
- Use the average of the hourly value for the two selected days. Exclude blinds or shades from the model. Include any permanent interior obstructions and movable furniture and partitions.
Option 3. Measurement (2-3 points, 1-2 points Healthcare)
Achieve illuminance levels between 300 lux and 3,000 lux for the floor area indicated in Table 3.
Table 3. Points for daylit floor area: Measurement
- Measure at appropriate work plane height during any hour between 9 a.m. and 3 p.m.
- Take one measurement in any regularly occupied month, and take a second as indicated in Table 4.
- For spaces larger than 150 square feet (14 square meters), take measurements on a maximum 10 foot (3 meter) square grid.
- For spaces 150 square feet (14 square meters) or smaller, take measurements on a maximum 3 foot (900 millimeters) square grid.
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