Choosing Energy Efficient Replacement Windows
Homes, no matter how old or new, suffer from the ineffectiveness of windows and glass in terms of protection from drafts and heat loss. As home energy costs continue to rise, concerned homeowners are becoming more interested in installing energy efficient building products.
The first thing you can do to improve the energy efficiency of your home is to install replacement windows; however, selecting the right window is not a simple process. There are several different types of energy efficient windows, each with its own thermal characteristics, glazing and frame type.
Glazing refers to the panes or layers of glass that fit into the frame. The more glazing a window has, the more energy efficient it is. Windows are classified as single- (one layer), double- (two layers) or triple-glazed (three layers). Manufacturers may hermetically seal air or gases between each glass layer, making it harder for heat to pass through. Coatings can also be applied either between the panes or on the exterior. The most energy efficient windows will have a barely visible low-emissivity or low-e coating that allows light though but blocks heat waves.
You can reglaze your old windows yourself rather than replacing them if you are comfortable with DIY home renovation projects. Get window glazing tips in this video by Columbia Water and Light:
Frames are commonly made from aluminum, vinyl (PVC) or wood. Each of these materials have its own strengths and weaknesses. Vinyl is the most popular window frame material due to its diversity, thermal properties and affordability.
Remember too that quality energy efficient windows will also carry the Energy Star label. This provides a fast, easy way to filter out competing brands.
The best way to compare different energy efficient windows is to look at four ratings that are grouped together on a sticker provided by the National Fenestration Ratings Council (NFRC). This NFRC sticker should be clearly visible on the window glass. The ratings include the following:
- Air Leakage (AL): This indicates the strength of the window seal. Air leaks are a major issue for windows and are obviously undesirable. Search for a replacement window with a low AL number.
- Solar heat gain coefficient: This measures the amount of heat the window lets in with the light. Ideally you want this number to be low, which indicates you are getting light without the heat.
- Visible Light Transmittance (0-1): This indicates the amount of visible light that passes through the window. The higher the number, the more light is transmitted.
- U-Rating (0.20-1.20): This measures the amount of heat that passes through the window per hour. The lower the number, the more efficient the window is.
