Guideline I.5: Lighting and Daylighting

During schematic design, work with owner/client to understand electric lighting needs and develop a strategy to meet needs while conserving energy and maintaining a high environmental quality. For each regularly occupied interior space, establish and document the light levels recommended for primary (and secondary) use type using B3 Lighting Space Tracking Worksheet.

Calculate target levels to maintain contrast ratios between spaces and surfaces as described above. For contrast ratios between work surfaces and wall surfaces (excluding fenestration), use the following calculation for illuminance ratio:

1:(Average work surface illuminance / Average wall surface illuminance)

For example, if the target average work surface illuminance is 40fc, the target wall surface illuminance should be at least 13fc to maintain the desired 1:3 ratio.

For contrast ratios between work surfaces and ceiling surfaces (excluding fenestration) use the following calculation for illuminance ratio:

1:(Average work surface illuminance / Average Ceiling illuminance)

For example, if the target average work surface illuminance is 40fc, the target ceiling surface illuminance should be at least 4fc to not exceed the 1:10 ratio.

Establish criteria for and document the interior surface reflections, based on manufacturer cutsheets, reflectance chart, or by using the calculation methodology described in IES Lighting Handbook. Specify the light fixture direction and lensing if following Recommended Guideline I.5F, Light Direction and Glare.

During design development and in construction documents, simulate electric lighting to confirm desired light levels at appropriate height, including wall or ceiling illuminance to confirm contrast ratios, and document results. Simulation of light levels should be completed for all regularly occupied spaces, and simulations should accurately reflect interior surface reflectance and include permanently installed furniture that may affect light levels. If needed, adjust lighting strategy to meet goals established in previous step.

During schematic design and design development, simulate the daylighting utilization in main spaces. Ensure that daylight models accurately reflect room size, height, window placement, glazing properties, interior surface reflectance, and permanently installed furnishings. If none of the following targets can be met, adjust the design to ensure compliance.

There are several daylighting metrics that may be used to comply with the B3 Guidelines and which are available as outputs daylight modeling software:

1. 1. • Spatial daylight autonomy (sDA) is an annual measure that determines the percentage of the floor area that receives the minimum light level required for at least 50% of the occupied hours. The threshold for sufficient daylight will be determined based on the recommended IES light levels for the program of the space.
      • Point-in-time daylight calculations to confirm light levels within 20% of IES recommended levels for 75% of regularly occupied floor area should be done at 9 a.m. and 3 p.m. on the equinox.
      • Daylight factor is the ratio of the illumination available inside a structure to the illumination outside, based calculated or measured from an overcast sky condition.

Compliance with this guideline may be documented using simplified daylight modeling software (e.g., Sefaira) which does not permit reflectance of materials if the following minimum area-weighted surface reflectance is achieved:

1. 1. • 80% ceilings
      • 50% walls
      • 20% floors

When selecting and/or specifying light fixtures, ensure that the criteria of CRI and RoHS compliance are met or mandated in specifications. This information can typically be found on manufacturers cutsheets.

If following Recommended Guideline I.5E, evaluate lighting plans and identify spaces with direct-only overhead lighting. Calculate the total connected lighting load in area served by the direct-only overhead lighting, and if direct-only overhead lighting exceeds 25% of the total connected load, select different fixtures to meet the criteria.

If following Recommended Guideline I.5F, select or specify interior surfaces with reflectance to meet or exceed the values listed. This information can be found on manufacturer specifications, typically listed as a fraction of percentage light reflectance or light reflectance value. If the manufacturer’s data does not include reflectance, use the methodology described in the IES Lighting Handbook to calculate the surface reflectance with a product sample or installed product.

Design:

1. 1. • 5A: Submit preliminary list of space’s IES levels and achieved measurements and maximum identified contrast ratios.
      • 5C: Submit preliminary daylight map or table of regularly occupied spaces documenting compliance with one of the listed paths.

Final Design:

1. 1. • 5A: Submit final list of space’s IES levels and simulated lighting level achieved by the designed lighting, including maximum identified contrast ratios.
      • 5B: Submit lighting schedule and specifications including a requirement for CRI of 80 and RoHS compliant fixtures.
      • 5C: Confirmation of inclusion of required daylight control devices. Final design daylight map, graphic, or table of regularly occupied spaces documenting compliance with one of the listed paths, including a surface area calculation of average reflectance if using simplified daylight modeling.
      • 5D: Submit lighting schedule and specifications including requirement for CRI 90.
      • 5E: Submit a narrative describing location and amount of direct-only overhead lighting.
      • 5F: Submit a narrative describing interior surface reflectance for each item listed.

Closeout:

• • • 5B: Provide documentation of installed light fixtures and compliance with RoHS.

‘Design for Daylight Performance’ Training Session Slides (PDF)

Appendix I-5: Lighting Attributes Worksheet

Architecture 2030 Palette – Daylighting Patterns and Guidance: http://2030palette.org/.

Building Energy Software Tools Directory (lists several hundred types of building analysis tools available to the designer, with a section on lighting, many of which include daylighting capabilities): http://buildingenergysoftwaretools.com/.

Efficient Windows Collaborative (contains references, resources and simulation tools for window design and selection for daylighting): www.efficientwindows.org.

IES Lighting Handbook, 10th Edition – Electric Light Level Recommendations, Surface Reflectance Guidance: https://www.ies.org/lighting-library/.

Radiance Lighting Engine: https://www.radiance-online.org/ and https://www.energy.gov/eere/buildings/downloads/radiance.

Sefaira – Dynamic Daylighting Metrics (explanation of the calculation of dynamic daylighting metrics): https://blog.sketchup.com/article/measuring-daylight-dynamic-daylighting-metrics-what-they-mean-designers.

Windows for High Performance Buildings (contains references, resources and simulation tools for window design and selection for daylighting): www.commercialwindows.org.

Velux Daylight Visualizer: https://commercial.veluxusa.com/inspiration/daylight-visualizer.

Regularly Occupied Space:

Any space that is occupied by one or more persons for more than one hour during days the building is in use. Note that this includes spaces which may be irregularly occupied but, when occupied, a typical occupant would spend more than one continual hour in the space. Excluded from calculation of continuously occupied spaces are:

1. 1. • Spaces with uses that only require minimal lighting and in which the primary activity intended for the space would be harmed by daylight (this exclusion does not apply to spaces with ultraviolet light concerns) – note that this only applies to the calculation of regularly occupied spaces with respect to the daylighting requirements.
      • Spaces that do not meet the minimum occupancy outlined above during daylight hours – note that this only applies to the calculation of regularly occupied spaces for the daylighting criteria with respect to the daylighting requirements.
      • Spaces where no individual occupant spends at least one continual hour during days the building is in use.