Building Better Performance
Glazing Can be a Key to Energy and Cost Savings
by Helen Sanders
According to the U.S. Department of Energy (DOE), windows
consume 30 percent of building heating and cooling energy and have an
even higher impact on peak demand and occupant comfort. Significant improvements
are needed in building façade performance, especially if the American
Institute of Architects’ 2030 commitment to carbon neutral buildings and
the DOE’s 2030 net zero energy goal are going to be met.
There has been some debate recently over whether we need to reduce the
use of glass in buildings. This is because, compared to walls, windows
have higher heat conduction and higher solar heat gain. However, the most
effective way of improving the energy efficiency of the façade
is not necessarily to reduce the window-to-wall ratio, but to implement
integrated façades that can save energy by optimizing the utilization
of natural daylight to offset electric lighting, which accounts for 20
percent of electrical energy usage in buildings. Integrated façades
combine automatically controlled dimmable lighting with the appropriate
amount of glass in the right locations on the building envelope.
To provide dynamic glare control, dynamic glazings or automated mechanical
shades with high-performance conventional glazing may be used. In fact,
integrated façades in combination with highly insulating windows
with dynamic solar control are key components of the DOE’s road map for
zero energy commercial buildings.
Glazing products with increasingly higher performance and capability are
becoming available, which allows for performance optimization of integrated
façade designs. For example, the use of triple glazing is becoming
more prevalent in northern states with U-factors in the range of 0.18-0.23
Btu/ft2.°F when one low-E coating is used (compared with ranges of
0.25-0.29 Btu/ft2.°F for dual pane low-E products with argon). The
performance can be increased further by using low-E coatings on two surfaces.
For further enhanced energy performance through variable solar control,
dynamic glazing products are available and cost competitive with conventional
solutions involving mechanical shading. These products provide a dynamic
response to the changing exterior environment, providing the means to
capture useful daylight when available, yet block the sun’s glare and
solar heat when required.
Even though it is not yet 2030, the high-performance glazing products
available today when combined with effective daylighting strategies already
have the potential to deliver high-performance façades, which maintain
the glazed area while improving energy performance and occupant comfort.
Additional information about energy-efficient glass and glazing is also
available on the Glass Association of North America’s website at www.glasswebsite.com/energy.
Dr. Helen Sanders is the vice president, technical business development
for SAGE Electrochromics and has served as the chair of the Glass Association
of North America’s Energy Committee.
Architects' Guide to Glass & Metal
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