A fan to stir up the whole outdoors? Not quite. But people who live in the Sunbelt, particularly, have discovered the distinct advantages of a whirling ceiling fan installed on a porch or patio, in a gazebo or summerhouse.Patricia Brandon, an ASID interior designer in Houston, says, ''People in this part of Texas love to enjoy their patios and gardens, but the weather is very hot, still and humid, and we have a big problem with bugs and insects. We do sometimes get a southeasterly breeze, but when people fence in their gardens for privacy they also cut down on the natural wind flow.''She recommends a ceiling fan for roofed-over outside living areas as well as for inside use. A ceiling fan also makes it possible for young children to play during the day, out of the sun, in an enclosed patio area that might be a dead spot for natural air movement.Jerry McAlpin, a designer of ceiling fans, says fans installed in a gazebo or outdoor structure should always have a protective roof over them so rain cannot come straight down into the fan. The connecting wiring should also be protected, he says, so it cannot be a direct source for rain to run down through the tube and into the fan. The motors of ceiling fans are coated in such a way that they can normally withstand the elements, but the above precautions must be taken.Mr. McAlpin claims it is not necessary to hire an electrician to install a ceiling fan, either inside or out. ''A do-it-yourselfer with any mechanical aptitude at all can install a ceiling fan,'' he says.Mr. McAlpin says surveys made by his company show that circulation of air, and the resultant energy savings, appear to be the most powerful motivations for buying indoor ceiling fans. Their use in outdoor living areas is more novel, but is increasingly recommended by designers , architects, and landscape planners. Wood-bladed fans dominate the market, he says, followed by wood/cane combinations, metal, and plastic.He contends that, to get the best usage, consumers should be willing to pay at least $150 for a quality fan, and that it should come with an optional light kit, so it can illuminate as well as create a breeze.Ceiling fans, first introduced nearly a century ago because they offered a dependable and durable way to circulate air around a room, have enjoyed a revival in recent years. Early models were heavy and noisy, and they almost disappeared when air conditioning came on the scene.Because of recent developments in solid-state electronics, ceiling fans today may be nostalgic, but many are also quiet, reliable, and energy-efficient. They are available in a wide range of styles.