It's more than the roofline, building materials, chimney, front door, and floor plan that dictate a home's character and architectural style. The windows — the eyes of the house — give a home its special look from both the outside and the inside.

For example, symmetrical double-hung windows are a key element of a Colonial-style house; rows of small windows accentuate the strong horizontal lines so indicative of Prairie-style design; and Palladium windows suggest the classicism Thomas Jefferson favored.

From a buyer's perspective, the type of glass, framing, and window coverings also can add a layer of appeal to a home. With a general knowledge of windows and their detailing, you can help buyers pinpoint the features they love — and ensure that windows in your listings will get noticed.

Popular Window Styles

Windows have played a prominent role in architecture throughout history. Consider the Palladian-style window, introduced by and named after Andrea Palladio, a 16^th-century Italian architect. This three-part window topped with a semi-circular arch grew popular in this country with Thomas Jefferson's embrace of classic architecture. It instantly connoted status and stability.

More recently, the style became de rigueur on many two-story, traditional McMansions. However, in recent years, the Palladian window has lost favor as its form was watered down, used on homes where it didn't stylistically belong, and proved difficult to fit with a covering, says William Calligari, an architect in Great Barrington, Mass.

In addition to Palladian windows, here are some other styles you'll frequently see:

• -  Double-hung windows have two sashes of glass that slide up and down vertically. Early double-hung windows had many panes of glass per sash and were called "12 over 12," meaning 12 panes per sash. This is a common type of window that is quite versatile, as you can open it a bit or a lot from either the top or the bottom.
  
• -  Single-hung windows have a single sash of glass. Single- and double hung windows may have grilles, which create the look of multiple panes of glass, also termed "divided-lite." Without grilles, windows appear more modern.
  
• -  Bay windows project from the side of a house, adding light and extra square footage to a room. The area inside a bay window creates a cozy nook well-suited for a window seat or a dining area.
  
• -  Bow windows also project from the side of a building like bay windows, only with more of a curved shape. These, and bay windows, can be picture windows that can't be opened or casement windows that open like a door.

These and other window styles are explained, with illustrations, in REALTOR® Magazine Online's Architecture Guide.

Scale Matters

When working with buyers, encourage them to look at a home's façade and study whether the window's size and proportions match the scale of other elements. Also, look at the windows from the inside of the home to ensure the rooms get enough natural light, says home design expert Marc Vassallo.

In his own 1922 neocolonial house in New Haven, Conn., the double-hung windows that were added by a prior owner provide inadequate light. "I'd love to add transoms above," says Vassallo, author of The Barefoot Home (The Taunton Press, 2006). A transom is a window over another window or door.

Perfect Framing

Just as a nice frame can showcase a simple photograph, a high-quality window frame can turn a pane of glass into a piece of art. Evaluate the frames closely, as damaged framing is a red flag that windows are old or not well-maintained.

There are four main types of frames, according to Bill Lazor, senior product manager, Simonton Windows, Parkersburg, W.Va., and Brian Hedlund, product marketing manager at Jeld-Wen Inc., Klamath Falls, Ore.

• -  Wood is considered by most to be the crème de la crème. Wood frames offer a traditional architectural look, can be stained or painted, and are energy efficient. Sealing prevents warping over time. If clad in vinyl, they're easier to maintain. Wood is one of the priciest selections.
  
• -  Vinyl has gained popularity for window framing because it's durable, energy efficient, and less expensive than wood. However, it doesn't come in a wide variety of colors.
  
• -  Fiberglass frames aren't very popular — at least not yet — because they're a newer product and on the expensive side. Their chief advantage is their durability.
  
• -  Aluminum is strong, can be painted, and is less expensive than other options. The downside? It's not thermally efficient.

What Glazing Can Do

Glass choices vary, too, affecting the way the window looks and how well it insulates the home from outside weather conditions.

An antique look can be simulated with restoration glass, which has slight waves, or with seeded glass, which contains tiny air bubbles. Glass can also be tinted in various colors to create a mood. If your listing has any special glazing, be sure to emphasize that in your marketing, as it may be just the feature that attracts discerning buyers.

With rising energy prices, buyers also value energy efficiency. Low-E (low-emittance) coating on windows improves insulation. Internal layers of argon or krypton gas further improve efficiency, and may be a big plus for buyers.

But how efficient windows need to be depends on where your buyers live. Triple glazing and krypton may be wise in Minnesota but overkill in Georgia, Lazor says. To know which window makes sense, check the Web site, EfficientWindows.org. Also advise buyers to look for the U.S. government's EnergyStar designation. A perk for potential sellers considering a window upgrade: Through 2007, home owners who install energy efficient windows and skylights qualify for a $200 federal tax credit.

Low-E glass offers other advantages. It blocks light to protect furnishings and deadens noise, says Kathy Kraftka Harkema, with Pella Windows & Doors in Pella, Iowa. Impact-resistant glass is much sought-after in areas prone to hurricanes and strong winds. This glass, similar to glass used in a window shield, also can thwart intruders.

Window Coverings

Shutters, blinds, curtains, and shades can drastically change the look of a room. In a home that's for sale, less tends to be more. Make sure that windows are unobstructed and let in plenty of light. The heavy green draperies that Scarlett O'Hara transformed into a dress lost favor long ago, as more home owners began to seek natural brightness and views of their landscape.

Today, wood blinds and shutters in neutral hues appeal to a range of buyers because they suit most decors and don't camouflage windows, says John Barnes, vice president marketing for Sunburst Shutters in Las Vegas. Faux-wood variations are less expensive and won't warp in bathrooms, laundries, and other rooms with a lot of moisture.

Sheer curtains or shades are another good solution, as they don't add bulk or block light. Both are also affordable choices.

But, remember, there's one window covering that's never in style — grime. Sparkling windows are far more important than nice window coverings in a listing. Ask sellers to pay special attention to make their windows squeaky clean, even if it means hiring a professional to do the work.

Sellers, Don't Rush to Replace

New, high-quality windows certainly will increase a home's appeal to buyers. However, sellers must seriously consider this costly investment. They probably won't see a full return on their improvement at the time of sale, says Tom Hopper, a salesman with Long & Foster's Bethesda-Gateway, Md., brokerage. Home owners should make this change only if they plan to stay put for several years before selling, he says.