Rating System

LEED BD+C: New Construction

Rating System Version

v2 - LEED 2.1, v2 - LEED 2.0

Inquiry

On this project, the space geometries are rather complex to allow a fair use of the calculation method using the geometry and height factors in Table 1 and Equation 1 described in the Reference Guide. Hence, we are using a daylighting simulation program (Radiance) to calculate the daylight factors for this project. The requirement for this credit states, "Achieve a minimum Daylight Factor of 2% (excluding all direct sunlight penetration) in 75% of all space occupied for critical visual tasks." To be able to assess the daylighting potential correctly as and as intended we would like to clarify the following: For any given space, should we calculate the daylight factors for points on a grid in the space and make sure that each and every point has at least a 2% daylight factor? OR For any given space, should we calculate the daylight factors for points on a grid in the space and make sure that the average of all the points is at least a 2% daylight factor? Which of the above calculation methods meets the intent of the credit? When we compared the daylight factors of a simple classroom design as calculated by the method outlined in the Reference Guide using Equation 1 and Table 1, with a simulation model of the space, we found that the results of Equation 1 are closer to the average daylight factor in the simulation as opposed to the minimum daylight factor in the simulation. When doing a simulation model to calculate the daylight factors: Do we lay out a grid of points across the entire space at the task height? OR Do we lay out the grid to reasonably exclude parts of the room that will not have tasks? For example in a classroom, the perimeter 2\' adjacent to the walls will never have a desk surface, so can we lay out the grid leaving out the 2\' perimeter of that room?