FRAME MATERIAL OPTIONS
Windows frames come in a number of different materials, including wood, vinyl aluminum, fiberglass and composite plastic.
Vinyl-frame windows are the most affordable. They're also especially energy efficient due to the honeycomb of chambers that boost insulating ability by trapping air. They can be built to fit any size opening. They never need repainting, though colors are limited.
Wood-frame windows are still an option. They're strong, beautiful and relatively energy efficient. As might be expected, good ones also cost the most.
They do require periodic maintenance.
They must be painted or stained periodically to look good and remain protected from against the elements.
Some manufacturers address that required upkeep by cladding the wood with vinyl or aluminum. The result is a tough, maintenance-free exterior and a natural-wood interior that you can paint or stain.
Aluminum-frame windows offer the low cost and low maintenance of vinyl versions; they're also durable. Aluminum-frame windows conduct heat easily, earning them a high U-value. The higher the U-value, the more heat a frame loses. Compared with vinyl or wood frames, which fall within the 0.3 to 0.5 range, aluminum frames can have a U-value as high as 2.
FIBERGLASS AND COMPOSITE
Fiberglass and composite-frame windows are the newest options. Made from materials similar to those on car bumpers, both are strong, maintenance-free and more energy efficient than vinyl.
Double-hung windows offer a classic look. They have operable upper and lower sashes. Lowering the top sash and raising the lower sash can allow warmer air near the ceiling to move out through the top while cooler air can flow in through the bottom. Many double-hung windows have sashes that tilt inward, allowing you to clean the exterior surfaces from inside your home. This feature is particularly valuable if the windows are on a second story.
Single-hung windows look similar to double-hung models, but only the lower sash is operable. As with double-hung windows, some models allow you to pivot the sash inward to clean the exterior.
Sliding windows have one or more panels that move horizontally along upper and lower tracks, allowing you to open up to half of the window for ventilation. They're easy to open and allow good ventilation.
Accent windows are available in a standard rectangular design or shapes that offer more visual variety, such as an octagon. These windows are usually fixed and don't allow ventilation.
Additional options are Sky Lights, Casement, Awning, Storm, Picture windows.
Some windows feature two layers of glass — double-pane — or three layers — triple-plane. Air or argon gas — which has better insulating properties — is sealed between the panes as an insulator.
Low-emissivity (Low-E) glass has a coating that allows light in, but blocks much of the heat that contacts it. A Low-E coating can help keep your home cool on a hot day by reducing the exterior heat entering your home.
The U-Value or U-Factor of the window indicates the rate at which heat flows through the window and frame and measures overall energy efficiency. A lower U-value means the window will insulate better.
Solar Heat Gain Coefficient (SHGC) is a specification that indicates how much solar energy passes through the window. A higher number means the window allows a higher percentage of solar heat to pass through.