As the name suggests, a three-season room, or a sunroom, is a porch which has been altered in order to keep the weather out. Three-season rooms are specifically designed to protect you from the wind, rain, and snow, but they are not heated or cooled. Not only does a sunroom keep the elements out, but it also offers a heated and cooled environment similar to any other room in your house. If you want a protected spot to breathe fresh air, but don't mind what the weather is like, consider a three-season room. Consider an all-season sunroom instead of a three-season room if you prefer to enjoy the sun in cold or hot weather.
The most cost-effective way to convert a porch or three-season room is to install glass and screen panels and a storm door between posts or columns. In addition, you can construct a three-season room with floor-to-ceiling windows and screens.
During the winter months in cold climates, a three-season room won't get much use since it is not insulated or heated. On those chilly days, late in the fall or early in the spring, when a porch would be uncomfortable, a three-season room can be heated by the radiant heat from the sun. Summer may be the off-season in some cases, since uninsulated, unaired spaces get too hot during these months.
Three-season porches have declined in popularity as a form of outdoor living in recent years. In the current economy, sunrooms are more affordable and practical than ever thanks to the availability of low-cost insulated glass windows and doors.