In some cases, you might need a permit for a window replacement, which is hard to get if you’re not a professional contractor. You should probably just hire a window replacement company in the first place because the job is complicated and can be dangerous for the average DIYer. You may not even save any money doing it yourself because contractors purchase materials wholesale.

In short, it depends. After 20 years, the glass in your windows is less energy efficient, which can cause increased electricity bills. You might also see signs of water damage or natural wear and tear over the years. However, with proper maintenance, some window frames can last up to 50 years, so you may only need to replace the glass to save on energy. 

At the same time, window replacement is a major investment, so replacing the glass in rooms most impacted by outdoor temperatures is one way to avoid going all-in to replace your windows.

Look for stickers at the top or inside of the frame, like in the tracks when the window is open. Some brands also stamp their name onto the frame itself or place it between the panes of glass, although this is less common. If you can’t find the info on the window itself, consider asking your neighbors or HOA.

No, it isn’t necessary to have energy-efficient windows. However, if you care about your energy bill and making your windows more energy efficient, fixing any heat, UV, or air transfer issues is an excellent way to lower your bills and keep your house cooler in the summer and warmer in the winter.