Adding a storm door that costs about $200 or less is generally a good investment if your existing door is old, but still in good condition. However, adding a new (or more expensive) storm door to a modern foam core door is not generally worth the expense since the added energy saved is very small. But you may have aesthetic reasons for wanting a storm door anyway. In any case, never add a glass storm door if the door gets more than a few hours of direct sun each day. The glass will trap too much heat against the entry door and possibly damage it.

Storm doors for patio doors are hard to find but they are available. Adding one to a modern multi-glazed energy-efficient low-e door is seldom economic. Insulated drapes, when closed for the night in the winter (or on sunny days in the summer) are also a good idea.

High-quality storm doors and windows use low-e glass. Frames are usually made of aluminum, steel, fiberglass, or wood (painted or not). Wooden storm doors require more maintenance than the other types. Metal-framed storm doors and windows might have foam insulation in their frames.

Some doors have self-storing pockets for the glass in summer, and an insect screen for the winter. Some storm windows have fixed, full length screens and glass panels that slide out of the way for ventilation. Others are half screen and half glass; these two components slide past each other. Some are removable for cleaning, others are not. All of these features add some convenience and higher costs.