My brother installs them for Four Seasons. They are expensive but they are very well built and last a long time. He has worked for the Tulsa one for 12 years or so. Let me know if you need anything.
Our house has an enclosed porch that acts like a sun room. We love it. Other than being a bit warm in the summer and cold in the winter, it's great. Not sure what the cost was, though, since it was here when we bought.
