855773644-LEED-v5-BD-C-Reference-Guide-Launch-Edition - Page 512

Extracted Content

Building Model

The model must be sufficiently detailed and complete to ensure accurate predictions of daylight performance. A simulation checklist must be used to support high-quality modeling practices. Checklist details are outlined in LM-83, Section 4. Details include but are not limited to:

• Exterior details, e.g., neighboring buildings/obstructions, trees, ground plane

• The orientation of the building, in relation to true north, is as designed.

• The geometry of the space is accurately modeled, i.e., wall thicknesses, angled ceilings, walls, fenestration surfaces, interior partitions and furniture.

• Blinds and window groupings and glazing properties

• Interior surface reflectance/material properties

• Local climate data, e.g., TMY weather data files

Daylight Performance Metrics

There are two daylight performance metrics that must be calculated: spatial daylight autonomy (sDA) and annual sunlight exposure (ASE). Both metrics are outlined in the Illuminating Engineering Society (IES) standard LM 83-23: Approved Method: IES Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE).

The sDA method assesses the prevalence of daylight over the course of a year. Calculate sDA for each regularly occupied space and calculate an average sDA across the total regularly occupied floor area. Include all regularly occupied spaces regardless of the ASE results. This approach intentionally differs from the calculation procedure outlined in the LM-83 standard to accommodate the wide range of project types and locations that pursue LEED. LEED associates points to daylit areas, despite the glare risk. Some designers find it confusing to exclude overlit areas from daylight calculations. Use sDA300/50%. for all spaces except areas without visual tasks.

REGULARLY OCCUPIED AREAS WITHOUT VISUAL TASKS Some spaces in the indoor environment are used for less critical visual tasks like walking through spaces or performing non-visually demanding activities. Adequate daylight in these spaces is 150 lux in LM-83 . These spaces may be identified by reviewing IES horizontal ambient illuminance design targets for spaces with illuminance targets of 225 lux or less. For these spaces, calculate sDA using sDA150/50% as an alternative to the standard sDA300/50%.

ASE assesses the risk of visual discomfort from too much sunlight in the space. There are two variations of ASE introduced in the 2023 version of the LM-83 standard. ASEnet is used for this LEED credit to encourage LEED projects to use automated glare control

U.S. Green Building Council LEED v5 Reference Guide for Building Design and Construction, April 2025 Launch Edition 502