In climates such as southern and central Arizona, including Phoenix, replacement windows can certainly make a noticeable improvement in the comfort level of your household and in your utility bills. As well as the benefits associated with energy and money savings, energy efficient windows in Phoenix homes also improve the look of a home, make it quieter, allow less dust to enter a house, protect the interior (carpet, rugs, floors, furniture, window coverings, art, pictures) from fading caused by ultraviolet light, let more light in and cut down on condensation on the windows.
Window Ratings
With greater than three hundred days of sunlight each year, how effectively a window prevents the heat and ultraviolet rays from the sun is essential. Energy Star windows are rated in five categories. The U-Factor and the Solar Heat Gain Coefficient determine how much heat a window transfers and are the key scores to concentrate on when looking for replacement windows.
Solar Heat Gain
Solar heat gain represents the percentage of the sun’s energy which is transmitted through a window. The sun’s heat is passed through the glass and the window frame and sash. The frame and sash can comprise 10-30% of the area of a window so the frame construction is an important determinant. Windows utilize a number of techniques to inhibit solar gain.
Low-E Coatings
Low-E coatings minimize the heat and ultraviolet rays that pass through a window. Low-E coatings are quite thin, invisible metal layers attached to the glass. High, medium and low solar gain versions of Low-E coatings are available. To further inhibit solar gain, some double pane windows have Low-E coatings on both pieces of glass.
Gas Fillings
Dual pane windows have a space between the pieces of glass. This gap can be filled air or gas (Argon gas or Krypton gas). Being denser than air, the gasses make it more difficult for hot or cold air to pass through. Krypton is the denser of the two gasses and needs a narrower space between the panes but is more costly. The gasses are non-toxic so a damaged window does not cause a health risk.
Window Frames
Vinyl windows frames are made with hollow spaces inside which can be filled with insulation to boost their thermal performance. Aluminum transmits heat very efficiently so aluminum windows have poor thermal performance without a thermal break. A material which transmits heat very poorly is positioned between the aluminum pieces on the inside and exterior of the window to create a thermal break.