855773520-LEED-v5-ID-C-Reference-Guide-Launch-Edition-1 - Page 340

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Occurrences of direct sunlight can be minimized with thoughtful design, but daylight glare and reflections will likely still be needed and desired by occupants for certain parts of the day or year. For this reason, it is highly recommended to also pursue Option 5. Path 1. Solar Glare.

This path uses a tiered point system with four thresholds of increasing stringency based on spatial Daylight Autonomy (sDA) calculations, indicating how much of a space receives sufficient daylight throughout the year. According to research conducted under the Illuminating Engineering Society’s LM-83 standard, spaces with sDA values of 75% or higher provide “preferred” levels of daylight, while spaces with sDA values between 55% and 75% achieve “nominally acceptable” daylight levels. The credit’s highest point threshold aligns with this research by requiring the preferred sDA level of 75% or greater.

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 [142], section 4. Details include but are not limited to:

• Exterior details, such as neighboring buildings/obstructions, trees, and ground plane.

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

• The geometry of the space being accurately modeled (wall thicknesses, angled ceilings, walls, fenestration surfaces, interior partitions and furniture, etc.).

• Blinds, window groupings, and glazing properties.

• Interior surface reflectance/material properties.

• Local climate data (TMY weather data files).

Daylight performance metrics There are two daylight performance metrics that must be calculated: sDA and annual sunlight exposure (ASE). Both metrics are outlined in the IES standard LM 83-23: Approved Method: IES sDA and ASE.

sDA assess 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 — for LEED associate 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 (see below).

142 IES Standard LM-83, https://store.ies.org/product/approved-method-ies-spatial-daylight-autonomy-sda-and-annual-sunlightexposure-ase/?v=0b3b97fa6688

U.S. Green Building Council LEED v5 Reference Guide for Interior Design and Construction, April 2025 Launch Edition 329