The need to conserve energy must start with each of us as individuals. The market can only function efficiently if we exercise our perogative within the system and demand building materials, technologies and systems that promote green building objectives and conserve energy.
Only 52% of windows used in new construction have windows that maximize energy conservation beacuse builders and consumers are unaware of the technologies that are available or fear that they are too costly. Some are, but glass technology has come a long way over the last 30 years and the cost of making energy efficient windows has come way down as the technologies have gained ground. There are also now rating systems and standardized tests developed by independent private associations and governmental agencies to guide the Architect, Builder and Consumer in selecting the window that will perform the best for the given locale you are building in.
Chief among these are the Energy Star Qualified products registry and the National Fenestration Rating Council. Energy Star ratings are supported and maintained by The U.S. Department of Energy. The NFRC registry is maintained by an non-profit industry organization that mandates testing protocols standards and designates independent labs to certify the performance of the windows of the participating manufacturers and Consumers and Building professionals can visit the sites to learn the specific attributes of a glazing system are most desirable for their location (what Zone they a are living in) so they can select a window that has been designed and engineered to best attain the desired levels of performance for their zone.
Each Energy Star Zone has specific minimum U-Values and Solar Heat Gain Co-efficients (SHGC) that they must meet in order to be listed as "Energy Star Qualified". There are also suggestions for specific optimum perfromance criteria there so that an individual can select windows that exceed the minimums and select the best combination of attributes for the windows in their home.
In general, those living in the Southern zones need to be more focused on SHGC measures because in these zones, cooling loads use the bulk of energy to regulate the homes temperature inside. In the Northern zones, U-Value is more important because heating uses more energy for keeping the home comfortable. If you live in Miami, it is more critical that you reduce the amount of heat gain coming through the glass and if you live in Detroit, it is more important to reduce the amount of heat loss through the glass. Fine tuning the glazing is important and can lead to reductions in heating or cooling costs of up to 30%.
Now most builders will choose the least expensive window they can to hold the price of the house down. It is up to the end consumer and local building codes to begin to consider life-cycle cost instead of initial cost in designating window performance levels. New technologies that make windows optimally efficient can be had for and average cost as low as $ 15.00 per window (source: Cardinal Industries, Inc.). The payback for a cost like this is less than a few years and has become very easy to consider given the rise in energy costs over the last few years.
So learn for yourself. Go to Energy Star Zones or Efficient Window Collaborative to learn what is the best combination of attributes and find a window that is best for your home.
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