Rating System

LEED BD+C: New Construction, LEED BD+C: New Construction, LEED BD+C: Core and Shell

Rating System Version

v2 - LEED 2.2, v3 - LEED 2009, v3 - LEED 2009

Inquiry

This project is pursuing EA Credit 1, Option 2. We are using the "Advanced Energy Design Guide for Small Office Buildings" (Achieving 30% Energy Savings over ASHRAE 90.1) in lieu of energy modeling, as allowed in LEED NC-2.2. Under the section for "Envelope / Vertical Glazing / Exterior Sun Control (S, E, and W only)", the recommendation for our climate zone (5) is a projection factor of 0.5 for a window with an SHGC of 0.46. Rather than providing exterior shading, we are proposing to use a window with a lower SHGC that will achieve similar performance. This approach is based upon Table 5.5.4.4.1 "Solar Heat Gain Coefficient Multipliers for Permanent Projection" from ASHRAE 90.1-2004, that lists multipliers for projection factors to meet Solar Heat Gain Coefficient requirements. To achieve a Projection Factor of 0.50, Table 5.5.4.4.1 gives an SHGC multiplier of 0.67 to arrive at the adjusted SHGC. The design guide requires an SHGC of 0.46 with a projection factor of 0.5 for our climate. Multiplying the SHGC of 0.46 by 0.67 gives an adjusted SHGC of 0.28. This project is proposing to use a window that meets the SHGC of 0.28 and eliminate the need for exterior projections.