Windows, if they are in relatively good condition, can be made more efficient by sealing the edges with caulk to prevent air leaks.  You can also weather strip doors to prevent drafts.  Storm windows and doors are also effective in keeping warm air in and cold air out during the winter months, and vice versa in the summer months.  Blackout curtains or insulating curtains also act as a barrier against drafts.

Replacing Windows

If your windows are old, you may be better off replacing them with energy efficient windows.  New technologies in recent years have allowed for increased indoor comfort level, decreased condensation, and decreased heat loss and air leakage.  In addition, windows glazed with low emissivity reduce solar heat transfer, but do not alter visibility through the window.

New Windows

If investing in new windows, energy savings can reach as much as 39%, depending on the window chosen, according to Efficient Windows Collaborative.  Not only do efficient windows reduce heating and cooling bills, they also allow for a reduction in the size of your HVAC system, which saves you money initially as well as from running a smaller system.

Tips

A few tips to keep in mind when choosing windows:

• Materials
• Resistance to interior condensation
• Window fit and dimensions

Resources

• Energy Efficiency and Windows (PDF)
• Choosing the Appropriate Windows for You (PDF)