Create an ideabook for your next remodeling project!
Browse more than 1,000,000 photos from top designers and save your favorites
Energy-Efficient Windows: Understand the Parts
You can save money and energy with today's windows — but first you need to know all the window parts and types
I write about interior design and architecture, and take what I learn into my own home (you may find me sanding and painting a kitchen table on the weekends). You can find my articles, published in Apartment Therapy, Architect, Eco-Structure, GRAY, Preservation, The Washington Post and more, at lindseymroberts.com.
I write about interior design and architecture, and take what I learn into... More »
Windows are the charmer of a house. They add that last touch of character that completes the house's style, especially if they're older windows.
But if your windows are a little gray around the edges, and it's impossible to update them for efficiency, then it's time to choose new windows. And because you're already replacing them, you might as well choose energy-efficient ones that will save you money.
The first step is deciphering all the acronyms regarding energy-efficient windows. The second step is understanding all the parts of a window — frame, glazing and operation — and how they contribute to a window's efficiency.
But if your windows are a little gray around the edges, and it's impossible to update them for efficiency, then it's time to choose new windows. And because you're already replacing them, you might as well choose energy-efficient ones that will save you money.
The first step is deciphering all the acronyms regarding energy-efficient windows. The second step is understanding all the parts of a window — frame, glazing and operation — and how they contribute to a window's efficiency.
Like it? Save it to your Ideabook »
Window Frames
A window's frame can be made out of aluminum or another metal, composite, fiberglass, vinyl or wood.
All have their advantages and disadvantages, but the U.S. Department of Energy (DOE) recommends vinyl, wood, fiberglass or composite. (Aluminum is easily heated, so it isn't a great insulator.) Wood has efficiency problems due to expansion and contraction, so consider aluminum- or vinyl-clad windows. But if you choose vinyl, consider an insulated version, depending on your climate and house requirements, for better thermal insulation.
A window's frame can be made out of aluminum or another metal, composite, fiberglass, vinyl or wood.
All have their advantages and disadvantages, but the U.S. Department of Energy (DOE) recommends vinyl, wood, fiberglass or composite. (Aluminum is easily heated, so it isn't a great insulator.) Wood has efficiency problems due to expansion and contraction, so consider aluminum- or vinyl-clad windows. But if you choose vinyl, consider an insulated version, depending on your climate and house requirements, for better thermal insulation.
Like it? Save it to your Ideabook »
Our acronym guide didn't tell you about all the parts of a window. Here's a diagram from the DOE.
|
by Tracy Stone AIA
»
Like it? Save it to your Ideabook »
|
| Window Glazing There are a variety of options for your window glass, too: gas fills, heat-absorbing tints, insulated (double- or triple-glazed), low-E coatings, reflective coatings and spectrally selective coatings. Gas fills. The most common gasses used are argon, which is relatively less expensive, and krypton, which is more expensive but has a better ability at decreasing a window's U-factor. Heat-absorbing tints. These come in colors such as blue, green, gray, bronze or black. Tint doesn't lower a window's U-factor, but inner glass layers or spectrally sensitive coatings can be added to help with that. Gray and bronze reduce heat and light; blue and green allow more visible transmittance (VT) but only slightly reduced heat transfer. |
| Like it? Save it to your Ideabook »
|
| Insulated. Double-glazed, triple-glazed, or storm windows allow space and air between panes (see the above diagram.) This lowers the U-factor as well as the solar heat gain coefficient (SHGC). In addition to air, space can also be added to lower the U-factor more. Gas fills or low-E coatings can also be added to insulated windows to further increase efficiency. Low-E coatings. These coatings increase a window's cost by 10 to 15 percent, the DOE says, but they can reduce energy loss by about 30 to 50 percent. The coatings reduce the U-factor but can also reduce visible transmittance unless it's spectrally selective. For hot climates or windows that get a lot of sun, the low-E coating should be on the outside of the glass. For keeping heat inside the house in the winter, the coating should be on the inside of the glass. |
| Like it? Save it to your Ideabook »
|
| Reflective coatings. These coatings block solar radiation but also VT and glare. They do reduce SHGC, though, which is a plus. The DOE says that this kind of glazing works better in hot climates, but since it does increase the need for indoor lighting, the energy savings can be minimal. This type of coating is good for special applications. Spectrally selective coatings. These coatings are great because they cut out 40 to 70 percent of the heat but still allow the light through. That means a low U-factor and SHGC but high VT. Spectrally selective coatings can be used to reduce the electric-based cooling needs of new houses in hot climates by more than 40 percent, the DOE says. |
Like it? Save it to your Ideabook »
Window Types
Last, consider the type of window you want in terms of how it operates, as some window types allow more air leakage than others.
Awnings, casement and hopper windows have lower air leakage than sliding windows. Fixed windows have no air passage at all, which isn't good if you occasionally want ventilation.
And for the future, keep your eye out for windows that pop out of the wall entirely. I recently talked to Denis Hayes, one of the organizers of the first Earth Day, and he has recently discovered that windows that pop out have the least air leakage, especially because the seal won't wear down over time like the other windows. He worked with a window manufacturer to produce some of these windows on a one-off basis, but they may be on store shelves in a few years.
Last, consider the type of window you want in terms of how it operates, as some window types allow more air leakage than others.
Awnings, casement and hopper windows have lower air leakage than sliding windows. Fixed windows have no air passage at all, which isn't good if you occasionally want ventilation.
And for the future, keep your eye out for windows that pop out of the wall entirely. I recently talked to Denis Hayes, one of the organizers of the first Earth Day, and he has recently discovered that windows that pop out have the least air leakage, especially because the seal won't wear down over time like the other windows. He worked with a window manufacturer to produce some of these windows on a one-off basis, but they may be on store shelves in a few years.
| Like it? Save it to your Ideabook »
|
| After you've made it through learning all the window jargon, you can go out and choose the style of your new windows to match the style of your house. All of these explanations won't make you an expert, but they should give you the vocabulary you need to talk to the window experts. |
| Are you replacing or repairing your old windows? Please tell us about them. More: Replace vs. Restore: The Great Window Debate Update Historic Windows for Charm and Efficiency Energy-Efficient Windows: Decipher the Ratings Contractor Tips: How to Choose and Install Windows |
Comments
mrsben Thanks Lindsey! Have bookmarked this for future reference as extremely informative.
12 months ago · Like
CoorItalia Excellent article. Please remember to check with your local building code what requirements exist in your county. We have done projects where the use of gas was not recognized, so money spent on Argon or krypton might have gone to waste. Other counties will give you a U-value target that must be achieved to pass final inspection.
12 months ago · Like
Lindsey M. Roberts Excellent point, CoorItalia. Always check your local building code and check with the proper building professionals before embarking on a project.
12 months ago · Like
Window Depot USA Central Ohio/ Conte Remodelers A home owner does well to understand U Value Ratings when comparing windows. The lower the U Value, the better for Northern climates. Southern climates use Solar Heat Gain data to compare. This is equivalent to MPG rating when buying a new car. Sorts out the 'hype' of Window marketers. Cuts to the chase quickly. Lots of great windows at fair prices with great energy ratings. 
2 months ago · Like
Ideabook updated on Sept. 24, 2012.
What are you working on?
News From Our Partners
Latest Ideabooks
People found the photos in this ideabook after searching for:
View over a million photos:
basements · bedrooms · dining rooms · entries · family rooms · garage and sheds · halls · home offices · landscapes · laundry rooms · powder rooms · wine cellars and more.
