Window treatments can obviously enhance the decor of your home, but they can also play an important role in reducing your energy bill. This article describes how blinds, drapes, and shades can each save you money.
 

Blinds

Window blinds have slats that can be horizontal or vertical, which can be adjusted to allow more or less light and air flow to come through (see types, costs, and reviews of window blinds). When fully closed, lightly-colored blinds can block and reflect sunlight from coming into the room, and therefore reduce heat gain by up to 45%.

If you have horizontal-type slats in your blinds, then you can adjust the angle of the slats so that they reflect light up onto your ceiling, which can bring light into the room without much heat or glare. However in the wintertime, because there are gaps between the closed slats, blinds don’t control heat loss as well as drapes or shades.
 

Drapes

During the summer, medium-colored draperies with white-plastic backings can reduce heat gains by up to 30%. And the pleats and folds of typical draperies can also help keep drapes cooler, because the pleats and folds lose heat through convection.

And during the winter, closing your drapes at night (or on windows which don’t receive much sunlight during the daytime) can reduce heat loss from a warm room by up to 10%.

To reduce heat losses by up to 25%, drapes should be hung as close to windows as possible, and should be allowed to fall tight onto a windowsill or floor. And similarly, you should install a cornice at the top of a drapery or place the drapery tightly against the ceiling. Further, the drapes should be sealed against the wall at both sides, and the drape material should overlap in the center. To attach the drapes tightly at the bottom, top, and sides, you can use Velcro or magnetic tape.

A drape's ability to impact heat loss and gain depends on several factors, including fabric type, thickness, color, numbers of layers of drape, etc. (see types, costs, and reviews of drapes).
 

Window Shades

Window shades can be one of the most effective window treatments for saving energy. For best performance, shades should be mounted as close to the glass as possible, and the sides of the shade should be tight to the window frame, to create a sealed air space which acts as insulation.

Quilted roller shades and some types of Roman shades feature several layers of fiber batting and sealed edges, and these work well for creating insulation and blocking the movement of air (see types, costs, and reviews of roller shades). Pleated or cellular-style shades create dead air spaces, which can increase their insulating value.

A somewhat more elaborate approach is to have two sets of shades, one dark and one white. During the winter the white shade is placed facing the inside of your home (to reflect heat back into the room), and during the summer the white shade is placed on the outside to reflect heat away from your home.
 

In General

Regardless of whether your window treatments are blinds, drapes, or shades, during the summer you should close your window treatments during the day to block heat from coming into your home, and you should open them at night (where practical) to allow heat from your home to radiate out. And it is just the opposite in the winter, when you should open your window treatments during the day to allow sunlight to come in to heat your home, and they should be closed at night, to help keep heat in.