Made with single-pane glass windows, a three-season room strikes the perfect balance between a screen porch and a four-season room, as it allows you to decorate like a regular room with nice furniture, flooring and decor — unlike a screen porch that requires sturdy, weather-proof furnishings. Plus, you can begin using a three-season room earlier in the year and well into the chilly fall months, whereas a screen porch has a shorter window or use. A three-season room can also be used in winter months, for things like special occasions, with the addition of an HVAC unit.
One final note: a three-season room can be upgraded to a four-season room.