When trying to find ways to live a ‘green’ lifestyle you can spend hours searching for ways to produce less waste and use less energy. Replacing your windows is actually a great way to reduce our energy expenditure. On average, windows take up 15 to 20 percent of the surface area of the walls. Because of this, windows are a very important component of home heating and cooling costs. What many may not realize is that windows lose more heat per square foot of area in winter and gain more heat in summer than any other surface in the home.
When you think about just how much heating and cooling can be flying out your windows, it’s no surprise why you’d be looking to replace them. Replacing your old, single paned windows with new high efficiency windows can actually save you $126 to $465 depending on your location and average energy usage.
Every window on the market today comes with a National Fenestration Rating Council Label. The label includes four ratings that all factor into the overall performance of the windows.
- U-Factor measures the rate of heat transfer and tells you how well the window insulates. U-factor values generally range from 0.25 to 1.25 and are measured in Btu/h·ft²·°F. The lower the U-factor, the better the window insulates.
- Solar Heat Gain Coefficient (SHGC) measures how well the product blocks heat caused by sunlight. SHGC is measured on a scale of 0 to 1; values typically range from 0.25 to 0.80. The lower the SHGC, the less solar heat the window transmits.
- Air Leakage (AL) measures the rate at which air passes through joints in the window. AL is measured in cubic feet of air passing through one square foot of window area per minute. The lower the AL value, the less air leakage. Most industry standards and building codes require an AL of 0.3 cf·m/ft².
- Visible Transmittance (VT) measures the amount of light the window lets through. VT is measured on a scale of 0 to 1; values generally range from 0.20 to 0.80. The higher the VT, the more light you see. Higher light transmittance can help if you are looking to also lower your lighting bills. You can swing open those curtains to allow plenty of light in and avoid turning on a light switch.
- Condensation Resistance measures how well the window resists water build-up. Condensation Resistance is scored on a scale from 0 to 100. The higher the condensation resistance factor, the less build-up the window allows. While this is not displayed on most windows it is still important to know. Built up condensation can not only be unsightly but lead to warming of wooden frames and mold growth.
In your search for energy saving windows, it is just as important to take the frame into account as well. If you have windows with great efficiency ratings but then pair them with a leaky frame that is prone to losing heat, you won’t be getting the most out of your investment. Not only do windows come with different efficiencies but they also have varying impacts on the environment during their construction.
Efficiency of Frames
Installing an energy-efficient window is necessary for saving energy, but it won’t do you much good if the window frame isn’t efficient as well. Generally, aluminum windows are the least efficient, even when they have a thermal window break in them. These windows simply conduct heat too well to be very efficient.
When searching for an efficient frame, there are four options available including composite, wood, vinyl, and fiberglass. Each frame type has advantages and disadvantages, so do your research to find out which frame will work best for you.
Materials used to construct window frames do have an impact on the environment. For example, wood windows raise concerns about forest management, because trees have to be cut down to make them. Plus, the frames require periodic painting and maintenance. Aluminum windows are energy-intensive to manufacture. They conduct heat readily but are easy to recycle.
Some environmental groups argue that vinyl is too toxic to be considered green. Vinyl is very stable, and there’s really not any human health risk to the homeowner. However, some of the chemicals that are made in the process of making vinyl and concern about its disposal at the end of its use.
The environmental impact of all of the window frames, including fiberglass and composites, is secondary to the thermal performance of the entire window. However if you are extremely concerned with your impact on our earth you may want to take these into consideration.
The Bottom Line
No matter which way you spin it, replacing your windows can have a huge impact on how much energy you use and save. There are plenty of options available today that feature some of the highest energy ratings ever seen.
To better determine what style of window works for you and to find replacement windows, talk to your local window professionals. Not only can they help you find the most efficient windows for you, but they can also ensure that they are installed correctly to prevent heat loss. Remember that window glass, frame and installation all matter when it comes to saving as much energy as you possibly can.