Provide for the building occupants a connection between indoor spaces and the outdoors through the introduction of daylight and views into the regularly occupied areas of the building.
Option 1 — Calculation
Achieve a minimum glazing factor of 2% in a minimum of 75% of all regularly occupied areas. The glazing factor is calculated as follows:
[INSERT FIGURE HERE]
Option 2 — Simulation
Demonstrate, through computer simulation, that a minimum daylight illumination level of 25 footcandles has been achieved in a minimum of 75% of all regularly occupied areas. Modeling must demonstrate 25 horizontal footcandles under clear sky conditions, at noon, on the equinox, at 30 inches above the floor.
Option 3 — Measurement
Demonstrate, through records of indoor light measurements, that a minimum daylight illumination level of 25 footcandles has been achieved in at least 75% of all regularly occupied areas. Measurements must be taken on a 10-foot grid for all occupied spaces and must be recorded on building floor plans.
Option 4 – Prescriptive
Use a combination of side-lighting and top-lighting to achieve a total Daylighting Zone (that floor area meeting the following requirements) that is at least 75% of all the regularly occupied spaces.
Sidelighting Daylight Zone:
- Achieve a product of the visible light transmittance (VLT) and window to floor area ratio (WFR) of daylight zone between the values of 0.150 and 0.180. Window area included in the calculation must be of the portion of the window at least 2’-6” above the floor.
- 0.150 < VLT x WFR < 0.180
- Ceiling should not obstruct a line in section that joins the window-head to a line on the floor that is parallel to the plane of the window and is, in distance from the plane of the glass as measured perpendicular to the plane of the glass, two times the height of the window head above the floor. See diagram below.
- Provide sunlight redirection and/or glare control devices to ensure daylight effectiveness.
[INSERT DIAGRAM HERE]
Toplighting Daylight Zone:
- The daylit zone under a skylight is the outline of the opening beneath the skylight, plus in each direction the lesser of: 70% of the ceiling height, one half of the distance to the edge of the nearest skylight, or the distance to any permanent opaque partition (if transparent show VLT) which is farther away than 70% of the distance between the top of the partition and the ceiling. See diagram below.
- Achieve a skylight roof coverage that is between 3% and 6% of the roof area with a minimum 0.5 visible light transmittance (VLT) for the skylights.
- The distance between the skylights shall not be more than 1.4 times the ceiling height
- Skylight diffuser with a measured haze value of greater than 90% when tested according to ASTM D1003. Avoid direct line of sight to skylight diffuser.
Exceptions for areas where tasks would be hindered by the use of daylight will be considered on their merits.
[INSERT DIAGRAM HERE]
In all cases, only the square footage associated with the portions of rooms or spaces meeting the minimum illumination requirements can be applied towards the 75% of total area calculation required to qualify for this credit.
In all cases, provide daylight redirection and/or glare control devices to avoid high-contrast situations that could impede visual tasks. Exceptions for areas where tasks would be hindered by the use of daylight will be considered on their merits.