South-facing windows let in the most sunlight and are desirable in all but the hottest climates.

North-facing windows provide soft, diffuse light.

Because of the low angle of the sun in the morning and late afternoon, light from east- and west-facing windows may be intense.

Glass isn’t good at conserving energy as an insulated wall, so glazed windows should be chosen carefully to preserve the home’s energy.

Storm windows and window coverings can help lessen heat movement, but the surest and most effective way to save energy is to utilize high-performance glazing. Look for windows that are Energy Star-compliant.

There are two ratings to look for: the R-value and the overall U-factor.

An R-value measures a material’s resistance to heat transfer. The higher the R-value, the better the insulating properties of the glazing.

The U-factor measures overall energy efficiency. It tells you the rate at which most heat flows through the entire window, door, and frame. The lower the U-factor, the more energy-efficient the window or door.

Insulating glaze typically has two, or sometimes three, panes of glass sealed together with either air or argon gas trapped between the two, which acts as an insulator. Some units have a plastic film suspended between two glass panes.

If the unit is properly sealed, condensation shouldn’t occur between the panes. Sometimes a drying agent called a desiccant is used in the spacer (the strip inside the panes, which helps keep them apart) as added insurance against condensation.

Low-Emissive (or Low-E) glazing has a film applied to one of the glass surfaces or is suspended between the panes. This coating or film allows light in, but prevents some solar rays from being transmitted through the glass.

A Low-E coating can help keep your home feel cool on a hot day by blocking longer-wave radiant heat from entering. On a cold day, it can prevent the radiant interior heat from escaping through the glass.

Tinted glass is given either a bronze or grey casts. It reduces glare and limits the amount of light and heat from the sun (solar gain) in your home.

Safety glass is a good option if there’s any risk of a person walking through a window. Tempered glass is heat-treated during the manufacturing process and crumbles, not shatters, if broken. Laminated glass has a film of plastic that holds the glass together if broken.