Have a combination of side-lighting and/or top-lighting that meets the LEED definition of a daylighting zone in at least 50% of all regularly occupied spaces. Given that this path is based on prescriptive design requirements that an existing building obvi

Have a combination of side-lighting and/or top-lighting that meets the LEED definition of a daylighting zone in at least 50% of all regularly occupied spaces. Given that this path is based on prescriptive design requirements that an existing building obviously would not have been designed and constructed to, buildings that comply via this path do so accidentally, and assessing the design against these prescriptive requirements would be difficult and time-consuming for most project teams. For example, the team would need to assess potential sidelighting daylight zones by:

• a) Determining which spaces within the building meet the LEED definition of “regularly occupied” for this credit
• b) Tracking down visible light transmittance value (VLT) for the installed glazing in the regularly occupied spaces, which is likely a difficult value to access in existing buildings
• c) Measuring the floor area and sidelighting glazing area (only glazing 30 inches above the floor) in the space to develop the window-to-floor area ratio (WFR). If electronic floor plans and interior elevations that allow for area take-offs are not available, all of these measurements would need to be performed manually.
• d) Multiplying the VLT by WFR. Spaces with values between 0.150 and 0.180 contribute to the credit if the other requirements are met
• e) Verifying that the ceiling does not obstruct a line in section that joins the window-head to a line on the floor that is parallel to the plane of the window. Without electronic design documents, this assessment would not be easy to perform or document. 
• f) Verifying that the ceiling does not obstruct a line in section that is twice the height of the window-head above the floor in distance from the plane of the glass as measured perpendicular to the plane of the glass. Again, this assessment would be nearly impossible to perform and document if electronic design documents are unavailable.
• g) Finally, the team would need to verify or install sunlight redirection and or glare control devices
• h) The above steps would need to be performed in and show compliance for at least 50% of regularly occupied spaces based on floor area. Where toplighting (e.g., skylights) contributes to daylighting zones, a separate, similarly arduous assessment must be performed.