Energy Saving Windows
|Energy Saving Replacement Windows|
|Identifying high quality energy-saving windows is a serious concern for homeowners who are preparing to purchase replacement windows for a home.|
Windows provide warmth, light and ventilation for homes. They can also enhance or negatively impact on a home's energy efficiency. Energy-efficient replacement windows create a more comfortable home environment and reduce the costs of heating and cooling a home. While steps can be taken to improve the performance of old, leaky windows, selecting high energy performing windows is the most effective way to improve energy efficiency. These windows, when properly selected and installed, minimize lighting and climate-control costs.
 Considerations for Selecting Replacement Windows
Selecting the right energy saving window option for a home involves considerations of architectural design, manufacturers, framing material, glazing options, window styles and installation requirements.
 Architectural Design
When choosing new windows, homeowners should consider which types of windows will work best in each area of the home. These considerations involve the question of whether the window faces the sun, whether rain and wind tend to blow against a particular side of the house, and into which room the windows will be installed. Specific window solutions exist to enhance different areas of the house including bedrooms, bathrooms, living rooms, kitchens, garage, garden room, home office, basements and attics.
There are dozens of window manufacturers who produce replacement windows. Identifying a window manufacturer who will provide the highest level of energy efficient windows for a specific window replacement job involves reviewing the manufacturer's standing in the American Architectural Manufacturers Association listings, reviews of Consumer Reports and other consumer advocacy organizations, evaluation of the percentage of the manufacturer's replacement windows which meet Energy Star qualifications and an examination of the manufacturer's standing in the home building and remodeling industry.
 Framing Materials
One of the most important aspects of a window's ability to withstand weather conditions and heat transfer is the window's frame material. Available framing materials include wood and wood-clad frames, vinyl, aluminum, composite and fiberglass frames. Wood frames are good thermal insulators but require frequent maintenance to withstand weather conditions. Aluminum or vinyl cladding can be attached to the exterior of the window frame to provide a window that offers thermal insulating properties as well as weather resistance. Fiberglass and composite frames are strong and durable frames which do not require any maintenance. Vinyl and aluminum frames are lower-cost frames but do not necessarily present the energy efficiency of the other frames, though the addition of foam filling and thermal breaks can enhance the energy efficiency of vinyl and aluminum frames.
 Glazing Options
There are a wide variety of glazing options that can enhance the energy efficiency of replacement windows. Many window manufacturers offer double glazing and triple glazing options in addition to the lower-grade single glazing alternatives. The multi-pane glazing often includes argon or, less frequently, krypton gas fills which enhance the insulating capabilities of the window. Additional glazing options include the glass itself which may be coated with a microscopic layer of Low E coating to inhibit the transfer of UV rays, help maintain a room's temperature in hot weather and protect a room's furnishings from harmful solar rays. There are a number of different types of strengthened glass alternatives for energy efficient windows as well as heat absorbing glass and self-cleaning glass.
 Energy Efficient Labels
Labels for rating the energy performance of replacement windows take into account a broad range of criteria. The Energy Star program was created by the United States Department of Energy which recognizes the importance solar energy in heating, cooling and lighting a home. Window labels and ratings provide a tool by which homeowners can review the available glazing options to ensure that their new replacement windows can maximize solar heat gain in the winter and minimize it in the summer.
 National Fenestration Ratings Council
The National Fenestration Ratings Council is charged with rating windows for the Energy Star program. The NFRC includes assessments of a window's U-Factor and solar heat gain coefficient in its ratings which are used when calculating Energy Star compliance. In addition, the NFRC also rates for visible transmittance, air leakage and condensation resistance.
The window U Factor measures the rate at which heat transfers through a window. The lower the U-factor, the higher a window's capacity to resist heat flow which provides a higher rate of insulation. The NFRC program uses this rating to measure the rate at which windows conduct non-solar heat flow as represented by the entire window unit including the including frame, glass and spacer material.
 Solar Heat Gain Coefficient
The solar heat gain coefficient (SHGC)measures the amount of solar gain that enters a house through a window's glass panel. This rating relates to the cooling season when solar energy can create a thermal heating load. Thermal insulated replacement window units allow the homeowner to reduce the energy needs and costs of cooling a home by blocking a portion of the solar heat gain. Different types of window enhancements, including Low E glazing, shade a window unit to lower the energy needed to cool a room.
 Visible Transmittance
The visible transmittance (VT) of a window unit indicates the amount of visible light that the window allows to be transmitted into a room. The VT measures the impact that the window's frame and glass has on this transmittance, with general VTs measuring between 0.30 and 0.70. High VTs transmit the most light so a homeowner who wants to maximize daylight will choose a window with a high VT rating.
 Air Leakage
Air leakage refers to drafts and air currents that seep into a house through a window. The Air Leakage measurement assesses the rate at which air leaks into or out of a room due to unsealed gaps that surround a window. The air leakage rating offers customers an opportunity to purchase a window that blocks air leakage to the highest possible degree. Air leakage ratings are expressed in units of cubic feet per minute. Windows which display low air leakage ratings are tighter than windows which have a higher air leakage rating.
 Condensation Resistance
Condensation forms when a light coating of water such as frost, water droplets, ice or a combination of these elements form on a window's surface. Condensation occurs when the exterior temperature drops significantly below the interior temperature of the home in conjunction with a high level of humidity. This "dew point" is the ideal environment for condensation to form on the window's glass surface. This is even more common in rooms that have humid conditions such as bathrooms and kitchens where condensation along a window's edge is more common. Condensation can damage home furnishings as well as the window itself, reduce visibility and add to moisture build-up within the house. The condensation resistance rating measures the rate at which a window will resist condensation.
 Tax Rebates and Refunds for Energy Efficient Windows
Many national and regional governments offer tax credits and/or rebates for energy efficient replacement window purchases. The goal of these programs is to encourage consumers to reduce energy consumption and expenses. The National Fenestration Ratings Council ratings are generally accepted as the standard by which the tax credits and rebates are awarded. Each national and regional authority offers its own tax incentive programs. These programs can often be used in conjunction with one another as well as in addition to other incentive programs. The qualifications are climate-specific, meaning that homeowners must purchase energy efficient windows which meet the needs of their specific climate.
 General Suggestions for Energy Efficient Replacement Windows
Strategies for purchasing energy efficient windows vary by window orientation, building location and regional climate. Homeowners should review these strategies before they purchase replacement windows.
 Southern-Facing Windows
Overhangs and other shading devices can prevent excessive heat gain in cooling-dominated climates and during hot seasons. For heating dominated climates southern-facing windows can be maximized with large glazing areas to enable the window to collect solar heat. These southern-facing windows should feature a solar heat gain coefficient of 0.6 or greater and a U-factor of 0.35 or less to enable the windows to maximize the solar heat gain and reduce conductive heat transfer during the wintertime. A high visible transmittance of between 0.30 and 0.70 will provide optimal daylighting.
 North, East and Western-Facing Windows
Windows on west-, east-, and north-facing walls should be minimized while still allowing for adequate light. Low solar heat gain coefficient rated-windows will help to control heat gain through these windows. SHGC can be lowered through a Low E coating which helps to control solar heat gain and loss in heating climates and with spectrally selective glazing and |reflective glazing. These low SHGC windows are also effective in keeping a room cool during the hot seasons and in hot climates.