22 August 2006
Minimize infrared transmittance by specifying a moderate to low shading
coefficient (SC) or low solar heat gain coefficient (SHGC) (50% or
Use high transmittance glazing greater than 60% to maximize daylight.
Glazing should also have a high thermal resistance ratio in order to
minimize heat gain.
Use clear glazing. Do not use tinted or mirrored coatings.
Table 4-1. Comparison of glass types. (from AlpenGlass Heat Mirror)
Sample Glass Types
Clear Double Insulating Glass
Laminated Glass (1/2" clear)
QUANTITY OF GLAZING. Through simple tools and modeling, glazing
quantities can be optimized in order to provide maximum daylight potential while
minimizing economic costs. Bring daylight in high through clerestories and top-lighting,
yet provide view windows for occupant benefits. Also, bring daylight in from two
directions if possible for balanced, uniform lighting.
Toplighting optimization varies between 3% and 9% skylight to floor area
ratio. The optimal amount of toplighting area factors in daylight contribution, cooling
loads, and potential energy savings. In order to calculate toplighting area optimization,
use a calculation program similar to "SkyCalc"13. Sunny climates with a cooling load
dominated environment will require less toplighting area than a cooler overcast
Ernest Orlando Lawrence Berkeley National Laboratory, "Glazing Selection", Tips for Daylighting with
Windows, The Integrated Approach, Section 4, p. 4-1.
New Buildings Institute, Inc. "Luminaires and Light Distribution, Daylight Systems", Advanced Lighting
Guidelines, Chapter 7. 2001 Edition, p. 7-31
The Heschong Mahone Group, "Optimizing Your Design", Skylighting Guidelines, Chapter 1, 1998, pp.
The Heschong Mahone Group, "Optimizing Your Design", Skylighting Guidelines, Chapter 5, 1998, pp.