Check out this style of green house. Looks like it would help in your heating battle....
http://energyfarms.wordpress.com/2010/0 ... ese-style/
http://www.roperld.com/science/solargreenhouses.htm
Here's something else to consider...
SHCS...How It's Done..!
Keep your fish and veggies warm, says the guy that lives in FL and gets cold @ 75.... :P