GreenYour Air conditioning
Lower the shades
Lowering the shades, drapes, or blinds can prevent unwanted heat gain through windows on hot days or help retain interior warmth on cold nights. It's a simple—but often overlooked—measure that anyone can take to reduce the energy costs and emissions associated with heating and cooling their home.
How to lower your shades effectively
In warm weather, cooling-intensive climates
- Lower your shades each day to provide more insulation against heat gain from outdoors, especially in south and west-facing windows.
- Keep shades down at night when attempting to preserve cooler interior temperatures.
- Choose light-colored shades to most effectively reflect sunlight during the day.
In colder, heating-intensive climates
- Keep shades open to admit heat from direct sunlight during the day, particularly in east-facing windows during the early morning hours.
- Leave drapes closed to retain interior warmth on cold nights or sunless days.
- Lower your shades to prevent unwanted heat loss through windows that receive no direct sunlight.
In all climates
- Lower your shades to provide additional privacy and noise reduction.
- Keep blinds, shades, and drapes open to take advantage of daylighting.
- Consider purchasing insulating shades to significantly improve resistance to heat transfer.
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Lowering the shades helps you go green because…
- It reduces the demand on your heating and cooling systems during peak usage periods.
- It requires no additional materials, expenditures, or construction.
- It can be employed as part of passive solar design solutions in many homes.
While interior shades are admittedly less effective at limiting heat transfer than exterior shading options, they offer a readily available, low- or no-cost means to improve a home's energy efficiency; however, taking advantage of this strategy requires daily effort and attention. Window shades can both reflect incoming solar heat (radiation) and insulate against conductive heat loss or gain. The US Department of Energy (DOE) warns that sunny windows can force your air conditioner to work two to three times harder than if no shading measures are taken; Light-colored shades reflect enough incoming solar radiation to effectively improve a window's solar heat gain coefficient (SHGC) by as much as 43 percent during warm summer months, while darker window shades tend to absorb solar energy and emit it as heat inside the home.
What if I want to upgrade my current window shades?
Lowering your existing window shades offers an accessible, inexpensive option for increasing energy efficiency; however, because conventional shades and drapes tend to be hung out away from windows, large gaps at the top and bottom of the drapes prevent them from reducing heat loss by more than 10 percent in most cases. Eliminating such gaps at the top and bottom—as well as at the sides and in the middle—of window shades boosts potential heat reduction to 25 percent, and employing multi-layered, insulated curtains or drapes will further reduce heat loss. Snug-fitting roller shades sit flush against the window pane and create an insulating layer of air, the effects of which can be enhanced by sealing the shade against the window frame on all sides, reducing heat transfer by approximately 45 percent.
Related health issues
Shades that are tightly sealed around a window frame may inhibit adequate ventilation and air flow, leaving windows more vulnerable to moisture condensation and mold growth.
- insulating shades: Heavy cloth or insulated panels used to cover an interior window opening and seal against heat loss.
- solar heat gain coefficient: Measures the fraction of solar radiation transmitted through a window. A SHGC rating between 0 and 1—the lower the rating, the less solar energy admitted—is assigned to either the glass alone or the window assembly as a whole.
- Lawrence Berkeley Labs - Using Windows Wisely
- Weather.com - Troubleshooting & Energy Efficiency
- US Department of Energy - Keep Your Cool and Save Money Too: Summer Energy-Saving Tips from the Department of Energy
- Alliance to Save Energy - Window Treatments for Energy Savings (pgs 7-8)
- Nelson-Young Lumber Co. - Guide to Understanding Condensation
- The Efficient Windows Collaborative - Glossary