Health experts have been warning us in recent years to stay out of direct sunlight whenever possible because of the possible long-term ill effects. But bringing the sunshine into the house can have some real health benefits.

A sunspace - a room that can be added on as a do-it-yourself project - brings added sunlight, reduces fuel costs and provides a growing environment for plants, said Lee Stanley, a designer at Solar Additions Inc., of Greenwich, N.Y.Sunspaces offer an excellent way to expand a house for a variety of uses - a work place for business or a hobby, a private retreat, an entertainment center - and are energy efficient because they capture and trap solar heat, he said.

Some scientific research has shown that people who own greenhouses and sunrooms can be healthier than those who don't have access to a steady supply of outdoor light, said Ken Bondi, a physiologist who also owns a Four Seasons Greenhouses Design and Remodeling Center franchise in Norwich, Conn.

"Natural daylight is a very beneficial `drug-less' therapy for conditions ranging from gloomy moods on cloudy days to colds, muscular aches and pain, and even, in some cases, migraine headaches," he said.

"The depressed, lethargic feelings that people suffer during the drab days of winter are not merely psychological. The listless, down-in-the-dumps sensation is directly related to the body's level of melatonin, a hormone created by the brain.

"Melatonin induces sleep and alters the secretion of other hormones essential to an energetic, bright outlook. Again, generous exposure to natural light can be very helpful in reversing the chemical effects brought on by gray days."

Standing on its own foundation, a sunspace attaches directly to a home. For gaining heat and light, it should face no more than 30 degrees to east or west of true south.

The outside wall of the home becomes the back wall of the new room. An existing door can provide access or you can expand a window into a door. Panels of front glass capture solar energy for winter heating. An insulated roof and side and knee walls allow for storage and utilization of heat.

However, do-it-yourselfers must think before they buy and build a sunspace, said Stanley, citing the "all glass greenhouse-type sunroom" as "an egregious example of lack of common sense that will provide anything but year-round comfort."

"A greenhouse simply does not make a good sunroom," he said. "Glass captures heat easily and loses it just as easily. So the all-glass uninsulated sunroom will be too hot on warm sunny days and too cold at night and on cool days.

"Common sense tells you not to put a glass roof over your home but some people buy them and build them - then discover the mistake too late."

Stanley had several suggestions for home remodelers considering a sunroom:

- USE WOOD. Sunrooms face higher than normal humidity levels, wide temperature fluctuations and extreme snow loads. Redwood and Southern yellow pine perform well in framing and support structures under such conditions. Metal doesn't.

- SLANTED GLASS will collect more sunlight than vertical glass. "The sun's rays hit slanted glass directly," said Stanley. "They hit vertical glass at an angle. Thus vertical glass reflects sunlight more than slanted glass. Yet people build vertical glass sunspaces and expect them to be as energy efficient as those featuring slanted glass."

- HIGH TOLERANCES. Because sunrooms face huge fluctuations in temperature and humidity, construction components must fit together at high tolerances. "Lacking proper tolerances, sunrooms will open up when they begin to heat up and cool down, resulting in water and air leaks," Stanley said.

- INSULATION AND VENTING. While a sunroom requires insulation, it also needs proper venting, said Stanley. "In recent years, construction has often erred on the side of over-insulating," he said. But a home must breathe, both for itself and for occupants who need fresh air.