Like many architects who design homes, when clients ask for windows flanked by shutters, I shudder.

Shutters have long challenged the modernist aesthetic sensibility of American architects, primarily because architects view most shutters as fakery.

Shutters seem especially alien to contemporary facade compositions because non-traditional window and door patterns, state-of-the-art construction materials and details, and sometimes complex exterior wall "topographies" do not lend themselves to shutters.

So why are shutters so ubiquitous?

Chalk it up to popular taste. Most Americans prefer traditionally styled homes, no matter how historically incorrect. And shutters are among the enduring hallmarks of traditional residential architecture. Once, shutters served a function. Today, most are inoperative, a kind of non-functional, referential emblem whose purpose is solely decorative.

Take away the shutters, though, and most homeowners are likely to feel that their houses appear naked, cheap and deprived of style.

Shutters on today's houses often share common characteristics.

They are usually too narrow in relation to window size. Even if they could be closed, they would not fit over the windows properly. Often shutters are placed only on front facades facing streets, not on visible side facades, and rarely on rear facades. This saves money but serves to underscore the role of shutters as pure ornament. And most are made of vinyl or aluminum, not wood, the material from which shutters historically have been fabricated.

Thus the modernist critique of ersatz shutters is partly about authenticity. If you want to live in a dwelling that aspires to look as if it were built 200 years ago, why not correctly replicate shutters installed 200 years ago?

But the architectural critique also relates to the original function of louvered shutters: to simultaneously provide privacy and natural ventilation; to filter daylight; and to help insulate against summer heat and winter cold.

In fact, operable shutters have long been a simple and effective architectural element. Fundamentally, they are environmental control devices.

With architectural sustainability becoming a major issue for designers, developers and builders, and increasingly a government policy concern, it's time to rethink shutters.

Why not use shutters that really work? With 21st-century technology, a modern shutter could contribute significantly to improving energy efficiency and comfort.

Operable shutters -- pivoting, sliding or rolling -- could have arrays of adjustable louvers to respond to varying environmental and human needs. Shutters could be made of different materials, even glass, which today can range from transparent to translucent to opaque. And shutters also could be an integral component of pre-engineered window systems, well insulated and detailed to form tight seals when completely shut.

When it's cold, or at night, shutters could be closed, either manually or automatically, to substantially reduce heat loss -- via conduction, convection and radiation -- through window frames and glazing. By trapping a layer of still air between shutter and window, and by blocking the wind, a shutter can greatly enhance the comfort of occupants.

When it's hot, shutters could be positioned not only to shade windows from direct sunlight, but also to insulate against heat gain through thermal conduction, in turn reducing air-conditioning loads and increasing comfort.

Of course, shutters can be opened and closed at will to frame views or ensure privacy, purposes they have served for centuries. However, for modern shutters to succeed, they must be designed to be opened, closed and adjusted easily. And they must be easy to maintain.

I don't doubt that a 21st-century shutter could be fashioned to look either traditional or contemporary. But no matter what the style, let's at least make shutters that are real, that do some work for us, and that contribute something measurable to our planet's sustainability.

Roger K. Lewis is a practicing architect and a professor of architecture at the University of Maryland.