In California, it's not considered living space, even if it's enclosed, if that's what you're asking. Enclosed patios have different code requirements (like no heat source is required) that prevent them from being considered living space.
I had an enclosed patio installed and talked with the appraiser about how it was counted when I sold the house. He said that it definitely added value to the home. But, that it didn't add anything to the square footage of the living space. Just like you don't add the square footage of an attached garage to the living space, unless you have converted the garage to living space.