Adding Storm Windows

Even though storm windows add little to the insulating performance of single-glazed windows (that are in good condition), field studies have found that they can help to reduce air movement into and out of existing windows. Therefore, they help reduce heating and cooling costs.

Storm windows are available for most types of windows. They can be installed on the interior or exterior of the primary window. They range from the inexpensive plastic sheets or films designed for one heating season, to triple-track glass units with low-emissivity coatings that offer many years of use. Mid-priced storm windows may use glass, plastic panels, or special plastic sheets that have specific optical qualities. Those made of polycarbonate plastic or laminated glass also offer a high degree of resistance to breaking during storms and/or from intruders.

For the most part, interior storm windows offer greater convenience than exterior storm windows. They're easier to install and remove; they require less maintenance because they're not exposed to the elements; and, because they seal tightly to the primary window, they're more effective at reducing air infiltration. Interior storm windows also are often the best choice for apartments and houses with more than one floor. If you can afford exterior storm windows, you can probably afford some newer, more energy-efficient windows, which will be a better investment.

Glass pane types offer better visibility and longer life than plastic pane types, but glass is heavy and fragile. In general, plastics are most economical for people with small budgets or who live in apartments. However, while inexpensive and relatively easy to install, they are easy to damage. Plastic panels, such as Plexiglas and acrylics are tougher and lighter than glass, but may scratch easily. Some may turn yellow over time as well. Some plastic films may significantly reduce visibility and degrade over time when exposed to sunlight.

Wood, aluminum, and vinyl are the most common storm window frame materials. There are advantages and disadvantages to all types of frame materials. Although very strong, light, and almost maintenance free, aluminum frames conduct heat very rapidly. Because of this, aluminum makes a very poor insulating material.

Wood frames insulate well, but they weather with age. They also expand and contract according to weather conditions. Wood-frame storm windows installed during the winter may not close easily during the summer, and those installed during the summer may fit loosely in the winter. They can also be quite heavy and thicker than metal frames. This can make storage difficult, reduce the view out the window, and reduce the amount of natural light in the room. Wood frames also require the most maintenance. There are, however, aluminum- or vinyl-clad wood frames that reduce maintenance requirements.

Vinyl frames are usually made of polyvinyl chloride (PVC) with ultraviolet light (UV) stabilizers to keep sunlight from breaking down the material. They, however, may expand and warp at high temperatures, and crack in extremely low temperatures. Also, if sunlight hits the material for many hours a day, colors other than white will tend to fade over time.

Installation

No matter what type you choose, the storm window frame must be hung square with the primary window and sealed to the opening. You should also consider the fact that they should be easy to move to allow for cleaning and ventilation.

Exterior-mounted storm windows must have weep holes at the bottom of the frame to allow any moisture that collects between the primary window and the storm window to drain out. Even though these drainage holes subtract from energy savings, not having them will eventually cause the primary window frame to rot, and possibly make them impossible to operate.

Caulking and Weatherstripping

Most experts agree that caulking and weatherstripping—two simple air sealing techniques—will pay for themselves in energy savings within one year. Applying these techniques will also alleviate drafts and help your home feel warmer when it's cold outside.

Before you use any air sealing technique in your home, you need to detect any air leaks. Then, you can select and apply either caulk or weatherstripping materials.

Window Treatments and Coverings

You can choose window treatments or coverings not only for decoration but also for saving energy. Some carefully selected window treatments can reduce heat loss in the winter and heat gain in the summer. They include:

Awnings

Window awnings can reduce solar heat gain in the summer by up to 65% on south-facing windows and 77% on west-facing windows. You can use an awning to shade one window or have an awning custom-made to shade the entire side of your house.

Blinds

Window blinds—vertical or horizontal slat-type—are more effective at reducing summer heat gain than winter heat loss.

Draperies

A drapery's ability to reduce heat loss and gain depends on several factors, including fabric type (closed or open weave) and color. With such a wide variety of draperies available, it's difficult to generalize about their energy performance.

In the summer during the day, you should close draperies on windows receiving direct sunlight to prevent heat gain.

Solar screens

Mesh window screens can diffuse solar radiation, reducing heat gain in the summer. Screens should be mounted in an exterior frame and should cover entire windows. They are particularly effective on east- and west-facing windows.

Window Shades

When properly installed, window shades can be one of the simplest and most effective window treatments for saving energy.

Shades should be mounted as close to the glass as possible with the sides of the shade held close to the wall to establish a sealed air space. You should lower shades on sunlit windows in the summer. Shades on the south side of a house should be raised in the winter during the day, then lowered during the night.

For greater efficiency, use dual shades—highly reflective (white) on one side and heat absorbing (dark) on the other side—that can be reversed with the seasons. The reflective side should always face the warmest side: outward during the cooling season and inward during the heating season. They need to be drawn all day to be effective.

Quilted roller shades, and some types of Roman shades, feature several layers of fiber batting and sealed edges. These shades act as both insulation and air barrier. They control air infiltration more effectively than other soft window treatments.

Pleated or Cellular Shades

Several manufacturers have designed two- or three-cell pleated or cellular shades with dead air spaces, which increase their insulating value. These shades, however, provide only slight control of air infiltration.

Window Shutters

Window shutters—both interior and exterior—can help reduce heat gain and loss. Interior shutters need a clear space to the side of the window when they're opened. They also require hardware that is fastened to the window jams or trim. Properly designed exterior shutters may provide the best possible window insulation system. Exterior shutters must be integrated into your home's architecture. Their mounting, drainage, and hinging will require special consideration, and it's easier to address these design issues in new construction.

Source: www.eere.energy.gov