The climate in Southern Nevada can be beautiful and also very harsh. From scorching summer afternoons to surprisingly cold winter nights, our homes shelter us from a wide variety of conditions. Many elements must come together in the creation of a comfortable and energy-efficient dwelling. Among the most important are windows.

Window technology has come a long way. In the not-too-distant past, windows were simply a way to let light in and keep wind out. They were not very good at keeping temperatures at bay, hot or cold. The overall effect of low-performance windows in an older home can be the equivalent of having a huge open hole in the side of the house. Technology has greatly improved the performance of modern windows, and they play a very important role in building efficiency.

New construction of an entire house or a room addition is the best opportunity for installing quality windows. Replacing windows in an older home can improve efficiency but may not be as cost effective as other strategies. Make your decision carefully. Sometimes, just the aesthetic improvement of new windows is enough of a reason. Others may do so when maintenance of the home becomes an issue. Whatever the reason, investing in good windows makes sense.

The simplest way to gauge a window's performance is the Energy Star label. They are about twice as efficient as the average window made a decade ago. The Energy Star window rating system varies by product and geographic location. Some windows are rated for the entire U.S. while others are considered Energy Star compliant only in certain areas of the country. Make sure you get the proper window for your area.

It can be helpful to know what makes an efficient, long lasting window. Manufacturers create various levels of performance and quality through selection of frame material and insulation, double or triple panes, inert gas fillers, special coatings and other technologies.

New homes commonly use dual-pane, low-e, vinyl-frame windows. Using two panes of glass, with a sealed air space between them, helps insulate the window. The term low-e refers to a special coating on one or more surfaces of the glass. The "E" in low-e stands for emissivity, which is a measure of heat transfer. low-e coatings actually block infrared or heat energy, while allowing visible light to pass.

Vinyl frames are very common because they are durable and relatively inexpensive. Frames are also made from wood, aluminum and fiberglass, or a hybrid of two or more of these materials. Looking at the life cycle and environmental costs is important. While vinyl may be cheap, it is toxic and not good for our environment.

Manufacturers can boost window performance by filling the gap between panes with an inert gas like Argon or Krypton. This strategy requires good seals to keep the gas from leaking out over time.

Ultra-efficient windows are now available that add an additional component called a Heat Mirror. This is a thin, transparent film mounted on the interior of the window. Super windows are now available that have insulation performance almost as good as a typical code-compliant wall.

No matter what kind of window you plan to install, in our climate it's a good idea to minimize them on east- and west-facing walls. If they already exist, shielding them from the direct sun is the next best thing. I prefer the natural approach with strategically planted, drought-tolerant shade trees, but awnings, porches and other methods are effective as well.

For more information about window technology and tips on selecting what's best for you, visit the Efficient Windows Collaborative Web site at www.efficientwindows.org. High-performance windows provide a good view toward the worthy goal of green living.

Steve Rypka is a green living consultant and president of GreenDream Enterprises, specializing in renewable energy, green building, alternative transportation and lifestyle choices for both residential and commercial clients. The company is committed to helping people live lighter on the planet. Steve can be reached via email at steve@greendream.biz or at www.greendream.biz.