Windows provide views of our outdoor surroundings, allow natural light to brighten our homes, and enhance the architecture of our homes.  In addition to all these great benefits, windows can generally account for up to 30% of the annual energy consumed in a home. Considering the fact that glass makes up almost 80% of a window, and dictates how that window will perform, it's important to choose the right glass when replacing windows in your home.

Look for Low-Emissivity (Low-E) Glass, which is treated with thin, transparent coatings of metal oxide and silver. Low-E glass does the following:

(1) Allows natural light to freely enter your home.

(2) During winter months, long-wave heat energy radiating from indoor objects is reflected back into the house keeping your home warm while lowering heating costs.

(3) In the summer, outdoor long wave heat energy, radiating from objects is reflected back outside, lowering cooling costs. It also reduces the penetration of ultra-violet rays to minimize fading of carpet and draperies.

Also look for glass options that offer gas fills. Argon and Krypton are colorless gases that are denser than air. They increase the insulating value of the glass unit as well as providing insulation from outside noise. These gases are odorless, colorless, and non-toxic.

A major contributor to your primary window wintertime condensation, beyond excessive home humidity, can be its insulating glass spacer. Just as important as the glass itself is the spacer that seals the edges of the glass panes. Traditional metal spacers can conduct heat and cold, causing condensation at the edge of glass. Warm edge spacers keep the panes of glass separated without acting as a conductor to help fight heat loss and reduce condensation.

Furthermore, all-foam warm-edge spacers, typically available in advanced triple-glazed systems (see diagram at right), can offer additional insulating U-value and R-value benefits.  Foam spacers inhibit heat escape paths at the glass edge, providing the best thermal performance. All-foam spacers also transmit very little sound compared to conventional metal spacers, keeping noise outside your home.

For vinyl windows, some manufacturers offer insulated mainframes and sashes to increase the window's insulating value. Look for an Expanded Polystyrene Insulation (EPS) option.

EPS is a thermoplastic, closed cell, lightweight, rigid foam plastic. It is the same material used in food industry packaging for its superior thermal insulating properties, and its solid form is used in rigid durable products such as TV and computer cabinets, appliances, toys, compact disc and audiocassette cases. EPS is also used for protective packaging and shipping of fragile items. As insulation in residential and commercial building products, EPS can provide an R-Value of 4 per inch (.25 U-Value per inch).

With today's high-performance window technology, you can have a proven solution to resist the sun's heat in the summer, and welcome it in the winter! There are energy-efficient windows on the market that are engineered to accommodate almost any budget, while providing the highest levels of year-round comfort and energy savings, making them well suited for virtually any climate. These high-performance windows are ?Green' because they use technology that helps lower your energy use. Lowering your energy use reduces air pollution, such as CO₂, that is emitted from power plants, thereby making a greener environment for everyone.

Green Frame Materials
PVC (vinyl) frame materials can be considered ?green' because they are recyclable and have a sustainable lifespan, keeping them out of landfills. Today's vinyl production is now sodium-based, not petroleum-based. PVC production does not require burning or generate harmful gases. Once they are installed in your home, vinyl windows are environmentally friendly due to their maintenance-free composition; they never require painting, sanding or refinishing.

Look for vinyl windows that are custom-made to fit the exact openings in your home, and ones that employ fusion-welded construction. Fusion welding prevents air leakage, water infiltration, and energy loss that are common with other frame materials on the market that are mechanically (screwed) or chemically (glued) fastened. Fusion welding also provides the best structural integrity.

Green Glass Solutions
When replacing windows, look for double pane or triple pane windows. Just upgrading your single pane windows to double pane can improve the R-value, or insulating value by 200%. But, the greatest thermal improvement comes with the addition of low-emissivity coatings, insulating gases, and warm-edge technology.

Low-emissivity coatings (Low-E) act like a filter. In summer, Low-E glass allows ample visible light to pass through while blocking infrared and ultraviolet radiant solar energy. The result? Rooms stay cooler in the summer. In the winter months, the glass helps to keep rooms warmer by reflecting heat back into the home. Adding Low-E glass to your double pane windows improves the R-value by 300% over single pane glass.

Air trapped between two or three panes of glass acts as an insulator. But for improved energy saving performance, the addition of Argon or Krypton gas to the air space provides greater insulating values. Argon and Krypton are non-toxic, odorless and colorless gases that create a thermal barrier between your home's interior and the fluctuating conditions outside. Dual pane windows with Low-E glass and Argon gas provide four times the insulating value of single pane glass. For the ultimate in energy saving performance, triple pane glass with Low-E and Krypton gas provides nine times the insulating performance of inefficient single pane glass.

Also, look for windows that utilize warm-edge technology. Warm-edge spacer systems seal the insulating glass units and flex with the glass in hot or cold temperatures to help prevent seal failures. These insulating spacer systems also keep the edges of the glass warmer, dramatically reducing condensation while keep warm air in and cold air out.