The current energy shortage is having a major effect on what homeowners are looking for in their homes. Not only do they want something that fits their tastes and matches their styles, they also need for their homes to perform better than ever. In an effort to keep utility bills low, homeowners are selecting building materials carefully and depending upon builders for their expertise. As a result, it is extremely important that builders are educated as to the best possible choices for each individual homeowner.
In recent years, manufacturers have introduced a wide range of energy-efficient window products to the building industry - from insulated glass units and thermal spacers to tinted glass and low-emissivity coatings. With so many product options available in the marketplace today, selecting a window can be a difficult task. What types of windows perform best in warm climates? Which windows save the most energy?
When determining which window is best for a particular application, look to a window's U-value first. The U-value is a measure of how much heat escapes through a window unit. The lower the U-value, the more efficient the window. U-values generally range from .1 to .9, with .1 being the most efficient.
Most window manufacturers use U-values when rating their windows, but the rating may not be based on the same factors for different manufacturers. Some manufacturers may give you a rating for the center of the glass, while others may calculate the rating for the entire window, including the frame. The entire window rating is what you should look at when comparing ratings of different windows.
Another rating to look for is the solar heat gain co-efficient (SHGC). SHGC measures the sun-shielding properties of a window, particularly important in warm climates where a cool indoor temperature is desired. The lower the SHGC rating, the better the product will protect from solar heat entering a home. In southern regions, glass products with lower solar heat gain ratings help keep annual cooling costs low. When looking at SHGC ratings, clear glass typically carries a rating around .80, whereas tinted glass has a rating of approximately .11. Tinted glass offers a host of benefits. It absorbs heat, thereby minimizing solar heat gain, reduces interior damage caused by harmful ultraviolet rays, and adds an element of privacy by decreasing visibility to a home's interior.
Low-emissivity (low-E) glass is fast becoming the product of choice among builders, remodelers and consumers looking for new construction and replacement windows. Emissivity measures the amount of heat is emitted from a window. The lower the level of emissivity, the more efficient the window. Emissivity levels generally range from 0 to 1.
