Your windows are the source of most of the heat/cold loss in your home. While upgrading all of them at once is extremely expensive I propose only upgrading one window per year.

The reason is cost beneficial for you. For example, if you live in a home with single pane or old windows replacing 1 a year can save you 3 – 5% of your heating costs (which works out to $30 – $50 / year.

There are other ways to save energy in your home that will save you more so keep that in mind when making the decision to upgrade your windows.

Here’s the different aspects of windows that you need to know in order to educate yourself about energy efficient windows.

The Frame
You may not realize it, but the frame around your window is almost as important as the window itself. The reason is that there are several different materials that windows are made out of and different materials are more or less energy efficient.

If you look at the windows in your house you’ll probably notice that the frame is made with vinyl (most of the white framed windows are vinyl). Vinyl is cheap, but is only recommended for temperate climates because vinyl can expand or shrink when it gets hot or cold. If you have vinyl windows you probably notice that each year new drafts seem to pop up… that’s because the vinyl has expanded and shrank and the silicone around it that seals the window has become detached.

The best frame to use is a wooden frame because it doesn’t conduct heat, but windows with wood frames are expensive. Aluminum is also used in cheaper windows, but since it’s a metal that conducts heat extremely well I don’t recommend you use it.

Fiberglass window frames are a good compromise. They are energy efficient and they have the added plus of the fact that they don’t expand or contract in heat or cold. The downside is that they are more expensive than vinyl windows, but the added cost is worth it.

The Glass
When window shopping look for windows that have an energy star label. While this isn’t a guarantee that they are the most efficient windows it does mean that they meet or exceed the guidelines set by the Department of Energy.

You’re also going to be looking for glass that’s been coated in low-emissivity (low-e) coating. These coatings serve two purposes depending what climate you’re in. In cold climates they help keep the warm air inside (energy savings is about 30% over single pane windows) and in warm climates they can reflect the sunlight to keep the room cooler (energy savings are about 40% over single pane windows).

Make sure that you understand that windows are rated by how much heat they let out AND how much heat they reflect. In a cold climate you’ll want one that doesn’t let heat out and lets heat in and in a warm climate you’ll want one that lets heat out and also reflects sunlight away. Talk to your window guy about the best compromise for your climate.

Cost Considerations
I don’t want to tell you that replacing all of the windows in your home is going to save you a ton of money right now. Energy efficient windows are expensive which is why I recommend replacing one per year, but only if the windows in your home are older than 10 – 15 years or they are single paned windows. If you have newer windows– even if they’re vinyl– it will benefit you more to focus on other areas of energy savings in your home. Keep these considerations in mind when making your decision to replace your old windows with energy efficient windows.