PoolEnc,
The typical cost of pool enclosures (glass) range from $50 to $100 per/ft^2 installed, including installation and yes you need a foundation! The larger your enclosure the lower the cost per foot. For your size of your enclosure it would be approximately $70 per foot, but that again depends on the options you want.
For cold climates you want to heat the floor for year round use and for colder climates you should add an air heater. At Covers in play they use the pool water to heat the floor and the air. They could not find anything on the market so they developed it themselves.
One other thing you should consider about an enclosure is how it opens. All companies sell enclosures that you have to push open, it will only take 10 minutes to open or so, less for the smaller ones. But it does take a lot of effort to push a building open. Check out the video at Covers in Play www.coversinplay.com it has a patent pending drive system that opens with a push of a button.
Hope this helps.
Pete
