In the past, effectively improving the quality and quantity of natural
light in your home often meant adding skylights or windows--but at the expense
of energy loss or heat gain. But now glazing technologies have begun to
catch up with the energy efficiency movement. Today you can use more glazing
to capture more light without yesterday's heat loss or heat gain problems.
The trick with glazing is usually to admit as much light as possible without
causing excessive winter heat loss or summer heat gain or glare--the factors
that, in the past, have limited window numbers and sizes. Heat moving through
windows destroys a building's energy efficiency and wastes our natural resources.
In fact, according to the Rocky Mountain Institute, a nonprofit research
and educational organization that fosters efficient use of resources, more
energy is lost through American windows every year than flows through the
Trans-Alaska oil pipeline.
The good news is that many new types of high-performance glazing have been
developed in recent years that make it possible to use a lot more glass
while minimizing heat loss, heat gain and glare. If you're building a house,
remodeling or replacing windows, you can choose from a wide range of options,
selecting glazing best suited to a particular window.
Talk with a window dealer about the specific properties and values available.
Generally speaking, if you want to minimize heat transfer, pick high-performance
glazing that has a high R-value. For maximum light, choose a type with a
high visual light transmittance value or, to cut glare, with a lower light
transmittance value. To cut heat gain, select glazing with a high shading
coefficient. Glazing with a high UV value will block nearly all furniture-fading
ultraviolet rays.
--Don Vandervort
