Windows are a beautiful and essential part of any home, but they also contribute to higher energy costs by heat gain in the summer and heat loss in the winter. This article explores ways to reduce heat gain and loss with window technology, window film and window coverings to help save you money.

 Window Technology: The two most important terms to know when buying windows are the U-Factor and Solar Heat Gain Co-efficient; both are measures of the window’s energy efficiency. The U-factor rates heat loss. The lower the U-Factor, the better the rating. The Solar Heat Gain Co-efficient measures heat gain by how much UVA and UVB light can pass through the window. Generally, the lower the number, the better the rating – depending on where you live.

While the Energy Star rating of a window starts at a U-Factor of .35, the current tax stimulus credit is for a U-Factor of .30 or less and a Solar Heat Gain Co-efficient of .30 or less. Those lower numbers are best in warmer climates. But in the Northeast, a Solar Heat Gain Co-efficient of .35 is more cost-effective because the cold-weather season is longer than the warm-weather season. In turn, more heat gain equals lower heating costs.

The construction material of the window is also important. The most energy efficient material is fiberglass because of its inherent ability to be a non-conductive material. The next best material is natural wood. Avoid vinyl and aluminum products, which transmit temperatures directly through their materials.

The type of window, whether encasement or double hung, contributes to energy efficiency. Encasement windows have a better seal than double hung windows.

Window Film: Window films block up to 99% of UV light that comes through windows, helping to cut down on heat gain. In summer, the ambient inside temperature can be up to 15 degrees cooler with treated windows. In winter, the window surface remains warmer, reducing the amount of heat lost through convection. Depending on the window film, there is a 15 – 25% difference in heat loss.

Window films can be tinted or clear, giving them the ability to block heat without blocking light.

Window Coverings: Like windows, window coverings have a rating value. The energy efficiency of window coverings is measured in R-value, like insulation. The higher the R-value, the more it will protect your home from heat loss in the winter. Shading Co-efficient is an important measurement for summer cooling, and it indicates the window covering’s ability to shade against heat gain. The lower the number, the more effective the shade.

Draperies and fabric Roman Shades create thermal resistance, with R-values ranging from 3.0 to 6.0. The R-values depend on fabric, lining, pleating and fit. For fabric, look for a tighter weave and thicker fabrics. Also, certain materials are inherently better at insulating. For example, wool insulates better than sheer fabric or cotton. Adding lining and interlining can significantly increase a shade or drape’s energy efficiency. There are many lining options, but thermal lining is created for energy efficiency. With a layer of acrylic foam, thermal lining keeps rooms warm in the winter and cool in the summer. Some thermal linings are also UV resistant and provide a degree of opacity to block sunlight. Consider pleating the curtains. The closer the pleats, the better insulation.

Finally, custom-fitted or air-tight shades and draperies are more effective because they create a dead air space between themselves and the glass.

Whether you plan on using window technology, film or coverings to reduce energy costs, consulting a professional will help you make the right decision for you and your home.

by Carrie Purcell, Contributing Writer

Special thanks:

Regina Sirico from Essential Glass Coatings, LLC,

www.essentialglass.com 866.264.8468

Matt Schardan from A.W. Hastings & Co.,

www.mschardan@awhastings.com 203.814.2236

Grace Horelik, from Window Expressions by Grace, LLC., 860.674.0587

Things To Know About Energy Efficiency

Understanding these common terms will help you select the right windows and doors.

U-factor – This measures the rate of heat loss and how well a product insulates. The lower the number, the better a product is at keeping heat inside a building. The U-factor is key in the winter months, and important to consider in choosing a window.

Solar Heat Gain Coefficient (SHGC) – This measures how well a product blocks heat from the sun. The lower the number, the better. In southern climates or high sun intensity areas, you might actually want to keep the sun’s heat out of your house. Windows can help do that.

R-value – This measures resistance to heat loss. Many people are familiar with the R-value because of its use in home insulation. But actually, for windows and doors, U-factor and solar heat gain coefficient are more important measurements.

Design Pressure Rating – The “DP” measures the amount of pressure a door or window will withstand when closed and locked. Each DP rating also establishes other performance factors such as water penetration; air infiltration; structural pressure; forced entry; and operational force. The higher the DP numbers, the better the performance. Look for the certified hallmark of the Window and Door Manufacturers Association.

Thanks to Marvin Windows at www.marvin.com and A.W. Hastings for the images used in this story and for this list of terms.