Depending on what’s covering your windows, closing your window treatments can reduce heat loss between 10-40 percent. The US Department of Energy reports that windows can account for 10-25 percent of your home energy bill. Caulking and weatherstripping windows and installing storm windows are critical for conserving indoor heat and should be done. After sealing leaks, homeowners should look to their window treatments as the next line of defense.
When you sit next to a bare window during winter, you feel colder. What’s happening is the warmed indoor air is cooling next to the chilled window pane and circulating back into the room. To conserve heat and save on energy costs, you can slow this process by lowering your window treatments.
Not all window treatments are created equally when it comes to energy conservation. Insulation is measured by R-value, which indicates the material’s resistance to heat flow. The higher the R- value a material has the greater the insulation. A bare, low-e, double-glazed window has a R-value around 3.5. Adding a window treatment can improve that number by as little as 10 percent and as much as 50 percent.
Cellular shades are ideal insulators and provide the highest R-value of window coverings available. Each cell traps warm air before it reaches the glass. The more cells, the better the insulation; but multiple cells reduce the amount of light that is filtered into the room, so it’s darker.