What Is It and How Does It Work?
The windows on your house can be great energy-savers, but they can also contribute to inefficiencies if they are old, leaky, or unshaded. Well designed window apertures can provide daylighting that helps limit the use of electrical lights, views to the outside, natural ventilation for fresh air and passive cooling, and beneficial heat gain during the winter.
What Are the Options?
Windows have very different payback periods in new construction than old. In new construction, more effiecient windows will pay back the difference in cost quick quickly. However in existing buildings, replacing the windows will provide minimal returns compared to other methods, such as storm windows and window coverings. In addition, check for draftiness around the window. Sometimes great savings can come from just adding caulk to the window frame or adding foam between the window panes.
In new construction or when replacing windows consider High Performance windows. They have a series of upgrades over traditional single-pane or double-pane windows with clear glass that help conserve energy and save money. While you can expect to pay more for high performance windows, the cost difference between windows with clear glass versus windows with multiple panes, selective coatings, inert gas, and other technological upgrades, can be made up in a relatively short period of time through energy savings. Windows are tested for several factors, and you should consider their performance on these tests when selecting energy-efficient windows. The tests are conducted by the National Fenestration Rating Council (NFRC) and are then used by ENERGY STAR in order to determine which products meet energy-efficiency standards. These figures will show up on a window’s label.
The factors to consider when buying new windows include:
U-factor
Solar Heat Gain Coefficient
Air Leakage
Visible Transmission
Low-Emittance Coatings
Air gap with Inter Gas
Storm windows are single-pane glass or plastic panels that can be installed on either the inside or outside of your existing windows. They do not offer a significant upgrade in the insulation of old windows, but they have been shown to decrease leaking and air movement around existing windows. Usually they are installed in cold climates as an extra measure to keep buildings warmer during the winter.
Storm windows are a low-cost alternative to replacing your existing windows with energy-efficient windows. The long-term savings will be lower than if you replaced your windows, but you will see a greater pay back due to the significantly lower cost of installation of storm windows. If you are on a tight budget or live in a rental unit but still want to increase your apartment’s energy efficiency, storm windows may be the answer.
As part of a comprehensive strategy to make your window systems as energy-efficient as possible, you can add window treatments and coverings to reduce unwanted heat gain in the summer and heat loss in the winter. Window coverings can be a small, but effective step in reducing energy use when paired with other effective strategies. If you are considering adding window coverings to your windows, you may also want to think about caulking and weatherstripping to prevent infiltration, adding storm windows, or installing high performance windows with multiple panes and selective coatings to prevent even greater heat gains and losses.
Options for window coverings include:
Awnings
Interior and Exterior Blinds
Draperies
High-reflectivity films
Insulating Window Panels
Mesh Window Screens
Overhangs
Window Shades
Window Shutters