8.5 Interior Lighting and Daylight
Key Takeaways
- Interior Lighting (1-2 points) splits into Option 1 (lighting controls providing 3 levels - on/off/midlevel - for at least 90% of individual occupant spaces) and Option 2 (4 of 8 lighting quality strategies).
- Acceptable lighting quality strategies include luminaires with luminance under 2,500 cd/m² between 45 and 90 degrees, light sources with CRI ≥80 (or IES TM-30 Rf ≥78), high surface reflectances (ceiling ≥85%, walls ≥60%, floor ≥25%), and lamps with CCT 2,700-3,500 K for at least 75% of total lamp power.
- Daylight (1-3 points) Option 1 uses simulation: spatial daylight autonomy 300 lux/50% (sDA300/50%) ≥55% earns 2 points, ≥75% earns 3 points, paired with annual sunlight exposure 1,000 lux/250 hours (ASE1000,250h) ≤10%.
- Daylight Option 2 uses simulation showing 300-3,000 lux for at least 75% (1 pt) or 90% (2 pts) of regularly occupied floor area on the equinox at 9 a.m. and 3 p.m. under clear sky conditions.
- Daylight Option 3 uses measured illuminance at 9 a.m. and 3 p.m. on a clear day in any month, with the same 300-3,000 lux thresholds applied to floor-area percentages.
EQ Credit: Interior Lighting (1-2 Points)
Intent: Promote occupants' productivity, comfort, and well-being by providing high-quality lighting.
Projects may pursue Option 1, Option 2, or both for a combined 2 points.
Option 1 - Lighting Control (1 Point)
For at least 90% of individual occupant spaces (private offices, workstations), provide individual lighting controls that enable adjustment to meet individual tasks and preferences with at least three lighting levels:
- On (full output)
- Off
- A midlevel between 30% and 70% of full lighting (continuous dimming or stepped switching)
For all shared multi-occupant spaces, provide presets, scene controls, or dimmable lighting accessible to the occupants of that space (not facility staff only).
Option 2 - Lighting Quality (1 Point)
Select 4 of the following 8 strategies:
| # | Strategy | Threshold |
|---|---|---|
| 1 | Limit luminaire luminance | ≤2,500 cd/m² between 45 and 90 degrees from nadir for 75% of installed connected lighting load |
| 2 | Light source color quality | CRI ≥80 (or IES TM-30 Rf ≥78 with Rg ≥95) for 75% of total connected lighting load |
| 3 | Surface reflectances | Ceilings ≥85%, walls ≥60%, floors ≥25%, work surfaces ≥45%, movable partitions ≥50% |
| 4 | Lamp life | Lamps with rated life ≥24,000 hr at 3-hour cycle for 75% of total connected lighting load |
| 5 | Direct/indirect lighting | At least 25% of total connected lighting load from luminaires with ≥25% indirect output |
| 6 | Lamp color appearance | CCT 2,700-3,500 K for 75% of total connected lighting load |
| 7 | Daylight responsive controls | Provide daylight-responsive controls in regularly occupied perimeter zones |
| 8 | View glazing for lighted spaces | At least 75% of regularly occupied floor area within 24 ft of view glazing wall |
EQ Credit: Daylight (1-3 Points)
Intent: Connect occupants with the outdoors, reinforce circadian rhythms, and reduce electric lighting use.
Use Option 1, 2, or 3. All options exclude furniture-mounted task lighting and assume blinds are open.
Option 1 - Simulation: Spatial Daylight Autonomy and Annual Sunlight Exposure (2-3 Points)
Use annual computer simulation to demonstrate:
| Metric | 2 Points | 3 Points |
|---|---|---|
| sDA300/50% (spatial daylight autonomy at 300 lux for 50% of occupied hours) | ≥55% | ≥75% |
| ASE1000,250h (annual sunlight exposure - 1,000 lux for 250+ hours) | ≤10% | ≤10% |
The sDA metric ensures enough daylight; ASE ensures not too much direct sun (glare control). Both must be satisfied simultaneously.
Option 2 - Simulation: Illuminance Calculations (1-2 Points)
Demonstrate through computer simulation that illuminance levels fall between 300 and 3,000 lux at 9 a.m. and 3 p.m. on both the vernal and autumnal equinoxes, modeled with clear-sky conditions:
- 75% of regularly occupied floor area meets the range → 1 point
- 90% of regularly occupied floor area meets the range → 2 points
Option 3 - Measurement (2-3 Points)
Measure illuminance on the floor plane after occupancy at 9 a.m. and 3 p.m. on any clear day in any month:
- 75% of regularly occupied floor area in 300-3,000 lux → 2 points
- 90% of regularly occupied floor area in 300-3,000 lux → 3 points
Provide automatic glare-control devices (blinds, shades, electrochromic glazing) for all regularly occupied spaces. The measurement option is typical when the design is unique enough that simulation models would be unreliable.
Choosing the Option
- Option 1 is the most rigorous and the easiest to defend with reviewers because it uses annual climate-based daylight modeling.
- Option 2 is a cheaper snapshot using two days a year. It still requires a simulation but uses simpler tools.
- Option 3 is the only path that requires post-construction site visits with calibrated illuminance meters.
An office project simulates daylight and reports sDA300/50% of 78% and ASE1000,250h of 7% across the regularly occupied area. How many Daylight credit points does the project earn under Option 1?
Which set of Interior Lighting Option 2 strategies meets the credit requirements?