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Dear Jim: I want a sunroom, but I cannot afford one so I thought about installing a bow or bay window. Is it better to buy a premade unit or assemble one from separate windows? What are important efficiency features?

-- Colin W.

Dear Colin: Installing a bay or bow window can be a relatively inexpensive improvement as compared to adding a sunroom. Depending upon its height and depth, it can dramatically increase the perceived size of a room and can function as shelf space for plants or even as a bright breakfast bar.

I recommend installing a complete bay or bow window unit as opposed to having one built from individual windows. The complete units seal well and are less expensive to install. You may even be able to install one yourself because the installation process is similar to any replacement window.

Another advantage of installing a complete unit is energy efficiency.The tight seals not only eliminate rainwater leaks, but also block air leakage. Most of the complete units have insulation built into the head and seatboards to reduce heat loss. This is also a plus if you plan to place potted plants on the seatboard because it keeps the soil near room temperature.

Bay windows are more commonly installed than bow windows. A bay window consists of glass on three planes. These are usually constructed from angled casement or double-hung windows on each side with a fixed picture window between them. The side windows are usually angled at 30 or 45 degrees from the wall. A 45-degree model provides a deeper seatboard. A bow window is typically constructed using four or more windows all tilted at different angles to create a curved, circular appearance. Just two or all the windows are operable and can be opened. Since more windows are used with a bow design, the installed cost is often higher than with a bay window. The complete bow units will be as efficient as the bay ones.

You will have a choice of the type of windows you want to use in a complete window unit. Casement windows are the best choice for several reasons. They are the most energy efficient because they close and compress the weatherstripping for an excellent seal. Double-hung windows use a sliding type of weatherstripping which is good, but not as effective as casements.

Casement windows also can be opened to any angle. This allows them to catch even slight breezes for better natural ventilation during the summer. Choose high-efficiency glass. Be sure it has a low-emissivity coating to save energy and reduce the fading of your carpeting. To block more outdoor noise, select glass with argon or krypton gas in the gap between the panes.

The following companies offer bay and bow windows: Andersen Windows (888-888-7020, Crestline (800-552-4111, Marvin Windows (800-346-5128,Simonton Windows (800-746-6686, and Weather Shield Windows (800-222-2995

Send inquiries to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit