Looking at (Not Through) the Window
Windows account for up to 30% of all residential heat gain and loss. The Department of Energy estimates that old, outdated windows result in some $35 billion in waste in the United States alone!
Who wants to be a part of that?
If you’re an average family, save up to nearly $600/year and eliminate more than 6,000 pounds of CO2 annually with new windows or repairs. Renovations also increase the value of your home.
When you’re ready to upgrade, keep these things in mind:
U-factor and SHGC
U-factor is a measure for how easily heat escapes. The numbers range from 0.2 to 1.2 -- the lower the score, the better in terms of insulation.
SHGC (Solar Heat Gain Coefficient) measures a window’s ability to avoid heat gain. This scale runs from 0 to 1 and, once again, a lower number is better.
Energy Star has put together a map to indicate the suitable U-factor and SHGC for windows depending on location.
Window Design
Design factors include shape, number of panes and type of glass. Beyond appearance, which is best? Fixed pane, casement, hopper and awning windows provide more energy efficiency than hung or sliding windows.
When it comes to panes, the more the merrier. Most windows in older homes only have one pane. Doubling or tripling the panes increases insulation and energy efficiency. Windows treated with glazes or multi-panes with gas infusions make them even more efficient. And, the better the window, the quieter your home.
Installation
The effectiveness of your installation will vary depending on the type of frame and type/extent of sealant.
There are five common framing materials: fiberglass, wood, vinyl, aluminum, and composite frames. Fiberglass lasts a long time but has air cavities (they can be filled with insulation,however, to maximize efficiency).
Wood frames are very high-quality and provide natural insulation, but they can warp with the weather -- which reduces their insulation value.
Vinyl frames often are more efficient than wood because they tend to contain insulation and are treated to resist moisture and UV damage; but, vinyl is made from crude oil.
Aluminum and other metal frames are extremely sturdy, require little maintenance and last a long time. But, because metal is a natural conductor, they don’t offer efficient insulation. And, the metal has to be mined.
Composite frames can be a good in-between choice for many because they are sturdier than wood, treated to resist moisture and reduce warping, yet do not conduct heat and cold like metal frames do.
Replace or repair?
No doubt about it, replacing windows costs a lot of money, creates a lot of waste, and requires that you consume a lot of resources. In the long run, it may be worth it. But, before going that extra mile, you might want to see what you can do to improve or repair the windows you have.
Inspect them for signs of mold or decay. Look for sagging, condensation accumulating in the winter, rattling with the wind, and any noticeable difference in temperature directly in front of a window.
If you see problems, try weather stripping and caulk -- it’s cheap and easy. The Department of Energy has a nifty guide to help you choose the right weather stripping material.
And, think about adding storm windows to achieve an effect similar to window replacement but with less cost. They’re less effective than having new dual or triple panes, but might be a reasonable next step after weighing all the factors.
Learn more ways to save on power with LADWP.
Learn more about the assumptions behind Magenta House water and power savings calculations.
DETAILS
Upgrade: Double-pane windows
Goal: Repair existing windows or install double-panes.
Potential Savings*: 830-3,500 KWH (kilowatt hours)/yr, $101-$583/yr after installation.
Skill level: ★★★
SAVINGS*
The average home savings calculation is based on the usage needs of a family of four and includes the following assumptions:
the home is switching from single to double pane, ENERGY STAR certified windows;
and all are installed and sealed properly.
Based on these assumptions, new windows can cost $3,000-$7,000 depending on the home.
Yearly energy savings amount to 830-3,500 KWH per house, or $101-$583 after installation and eliminate 1,006-6,205 pounds of CO2.
