Daylight Option 2- Borrowing Light

Borrowed light scenarios are only accepted to demonstrate credit compliance when using either simulation or measurements. It has never been accepted in either version when using either the prescriptive method or the glazing factor calculations.

The prescriptive method in v3 and the glazing factor calculation in v2.2 is a simple geometry and there is no means with those calculations where you can consider the daylight illuminance levels with borrowed light levels.

The LEED v2.2 Reference Guide states that when analyzing complex geometries, simulation or measurements should be used. You may see a comment from a reviewer that says this,"However, the provided drawings indicate that some of the project's interior spaces are receiving daylight using borrowed light strategies (i.e. sidelights, glazed transoms, etc.) The glazing factor calculation is designed for simple geometries and provides default data to support a simplified analysis. As described in the LEED-NC v2.2 Reference Guide, when analyzing more complex geometries, it is necessary to use daylight simulation or light measurements to demonstrate meeting the credit's requirements."

Same with the prescriptive method in v3, where you may see a comment like this,"However, the provided drawings indicate that some of the interior spaces of this LEED-NC project are receiving daylight using borrowed light strategies (i.e. sidelights, glazed transoms, etc.). The prescriptive calculation is designed for simple geometries and provides default data to support a simplified analysis. For a more detailed analysis, a daylight simulation or light measurements are appropriate means to demonstrate meeting the requirements of this credit. To document compliance using a simulation model or light measurements, projects must document that a minimum of 75% (90% for two points) of the occupied space achieves a minimum 25 footcandleis at 30 inches above the floor.

At one time in the interpretation database, there was a LI that indicated that hand calcs cannot be used for borrowed light scenarios, i looked for it and it appears to be gone, or maybe I'm not putting the right parameters into the search column. It really is no longer an easy to use database.