Older sliding glass patio doors might be costing you money..

Older sliding glass doors were usually one pane of glass and lacked a thermal break — an insulator between the inside and outside parts of the frame. Also, because they slide, sliding glass doors tend to leak air around their weather-stripping and that weather-stripping tends to break down over time. This means that older sliding glass doors often let in hot air in the summer and cold air in the winter, increasing your energy costs and creating drafts in their vicinity.

New patio door designs solve many of these problems. They insulate better, because they're usually double-paned glass with an inert gas such as argon in between the panes. They have low-emissivity (low-e) coatings, which reduce heat flow through the glass. New energy-efficient metal doors have a thermal break between the inside and the outside, so that the metal doesn't get cold and "sweat" condensation.

In addition to sliding doors, French-type patio doors are increasingly popular. Both traditional French doors — two doors that both open - and doors that have one fixed panel and one panel that opens are available. Either type of door is generally more energy efficient than a sliding glass door, because the weather-stripping can seal more effectively. The new sliding glass doors slide more easily and provide better protection from intruders. The better quality new doors have locking systems that latch the door in several places. The multipoint locks also hold the door more firmly in place, helping to reduce air leakage.

Traditional-style windows have true divided lights made of separate panes of glass. This style is less energy efficient, and many manufacturers no longer make patio doors in this style. Divided lights can be simulated by a grid attached outside of the window or between the two panes in double-paned glass.

Installing a patio door can be a do-it-yourself project, but you need to measure correctly and follow the manufacturers' instructions. Trimming parts of the door to make it fit could also remove some of its energy-efficiency features.

The main factor in patio door efficiency is the type of glass. Look for an Energy Star® label, showing that the door meets the U.S. Department of Energy's energy-efficiency standards. A door meeting those standards will generally at least have double-paned windows with low-e glass. Some manufacturers offer tinting and coatings that help the glass stay clean. You can compare the energy efficiencies of different patio doors using the rating system of the National Fenestration Ratings Council (www.nfrc.org).

Take a look at the new styles of patio doors. You might find one that improves the look of your home — and your energy bill.

New Materials for Patio Doors

A variety of materials are now available for patio doors. While aluminum used to be standard for sliding doors and wood for French-style doors, these doors are now also available in vinyl, steel and fiberglass. Many doors are available with these low maintenance materials on the outside and traditional wood on the inside.

The newest material for patio doors is fiberglass, which is durable and energy-efficient and can be painted or stained. Solid vinyl-frame patio doors offer the virtues and vices of vinyl siding - it can't be painted, but it looks good for years.