| NZB: DAYLIGHTING |
Diversity Good in Solar Control Too The benefits of the sun and natural light are many, but as with anything, there is a downside, notably glare and solar heat gain. Glazing can go a long way toward achieving desired daylighting effects, but more than not, integrated shading systems are necessary to manage the latter issues.
Barbara HorwitzBennett has been reporting on the architectural industry for the past 15 years. She covers glazing and daylighting for Architectural Products, and in 2011 contributed to an important industry white paper on net-zero buildings.
hile glazing technologies continue to offer better performing solar heat gain coefficients (SHGC) with better visible light transmission (VLT), glazing alone is often insufficient to deliver the daylighting levels, heat gain and glare control desired by most building owners and architects. Yes, glazing can be specified to promote daylighting and either optimally block solar heat gain in the summer when it is unwanted, or promote it in the winter when it is desired, but not both. Furthermore, it is difficult to control glare as the path and direction of the sun is constantly changing throughout the seasons. “Glazing alone will generally not provide effective glare control and address the issues arising from low sun angles to the east and west and during the winter months,” explains UK-based Draper Consultant Richard Wilson, B.Sc. While an impressive SHGC of 0.20, or even lower, can be achieved with high-performance glazing, this also means that the VLT will need to be in the range of 10%–30%. The downside is that optimized solar control comes at the expense of natural lighting, explains Wilson. Furthermore, a low SHGC means that the benefits of solar heat gain will not be realized during the winter months.
Daylighting Team Coordination In order to ensure that daylighting performance and comfort is optimized, according to Christopher Hagen, regional sales manager, southwest region, Hunter Douglas Architectural Window Coverings, San Diego, it is essential for the design team to work closely with glazing and shading manufacturers. Through this process, the team should initially consider factors such as climate and geography. “Next, we’ll often discuss the levels of glare control and thermal comfort someone needs, including a look at how interior spaces will be used, and consider the aesthetics/ curb appeal of the exterior,” he explains.
Abudant natural light has its benefits, but with anything, there are drawbacks, most notably glare and solar heat gain. Glazing and integrated shading systems are necessary, and It is imperative to work closely with glazing and shading manufacturers.
“In our experience, designs that attempt to achieve desired thermal and visual comfort through glass selection alone, generally fail to meet the mission, and often result in spaces with significant glare and/or thermal discomfort,” relates Dr. Brent Protzman, LC, CEM, director, building science and standards development, Lutron Electronics, Coopersburg, Pa. “The overall thermal and visual performance of an integrated façade is dependent upon a combined glazing and shading solution.”
34 | 03.18 | NET ZERO BUILDINGS
Highlighting the Path Toward Net Zero Building Design.