My goodness, this thread takes me back in time! Mighty_turf, I ended up not using a solar cover on my 10x12 HFGH (decided my climate really didn't require it) so I am no help on best places to purchase. I believe conventional wisdom is that most heat loss in a greenhouse occurs through the roof. If I were to purchase one I'd definitely cover the roof, and probably lap it down the sides a bit, depending on the size I ended up ordering. Hopefully others here will have more specifics for you. If not, I'd consider starting a new thread with your specific questions about solar pool covers, to get a few more eyeballs on your questions. (Sometimes newer threads get more attention...?) Happy New Year!

karenrei, I don't have a hoophouse, each wall and the roof are totally seperate segments as to R value, covering etc. stressbaby nailed it on the head on this thread http://forums2.gardenweb.com/forums/load/strucs/msg0909104730738.html and I am surprised that thread did not get more input. Identify areas where improvement can be made and fix them. Then look at the whole structure again and work out where the "new hole" is. On the thread about the polystyrene sheets, http://forums2.gardenweb.com/forums/load/strucs/msg081128491250.html I tried to point out that adding an R3 insulation to one wall was great, bumping it up to R6 may be a waste of money because there may be another place you could put some R3. Yes, In retrospect my south roof (and sorry to use trade names but people can look it up and understand it better) should have been Tufflite IV outer, pool cover and then Tufflite infrared on the inside. A nice sandwich and cheaper and easier to install then polycarbonate triple wall. Yes I know polycarbonate triple wall will last longer but, it is also very expensive. I had a standard double poly inflated south roof so I gained some insulation advantage but all of that insulation was lost by a breach of the outer layer. (see my rant on this thread) http://forums2.gardenweb.com/forums/load/strucs/msg0409365924489.html OK, so I know I am going to lose light on the south roof because of this sandwich but I am going to get a boost in insulation, and because of the bubble wrap sandwich I am also going to get some protection from damage. The sections would be 2ft by 8ft and if I had a breach of the outer skin then my south roof loses 1/12 of its R value not 100%. Next, as in reducing light transmission, as you say most of the light in spring is through the south wall, so a reduction in light transmission in early spring of say 15% from the south roof is still a loss but a small loss as not much of the total is coming in that way. ""any areas that don't get much sunlight being as heavily insulated as you can with opaque (preferably reflective, in my opinion) insulation."" North wall is solid and painted white inside (reflective). Half the north roof is solid. Changes to my configuration next spring? 1, Shade cloth hung vertically inside about a foot from the south side to reduce the tendency of young plants to grow towards the south side but as the shade cloth is on the inside it will block light to the plants but still contribute to raising the air temperature in the greenhouse. 2, Wait until the corn and bean crop is harvested and there is snow on the ground and then set fire to my old barn to the south where the shingles that hit my greenhouse in high winds come from. (insurance company please note, that was a light hearted attempt at humour.) Umm... on second thoughts, I will insure my greenhouse! :)

aezarien is right. A black cover would plunge your GH into darkness, at which point, you might as well shut it down for winter and move the plants into the house. As for leaving the aluminet up all year: If you experience so much sunlight you need shade in winter; are you sure you even need a solar cover? You might do as well by permanently lining your GH in bubble wrap, which will keep it warmer in winter and cooler in summer. Sort of like going from lightweight double to heavyweight triple polycarb, which may well be all you need in your climate.

After looking at my situation I decided to just keep my pool cover on my green house all Summer. Here is why: The Green house temp was 120+ even with both exhaust fans going. Nothing can grow at that temp. I did figure out a way to role up one side of my green house to help cool it next summer. Plus I am thinking of adding a mist system to help cool it down. When it comes to Winter, I just purchase a pool cover that is 14x28 which is enough to cover both ends of the green house which was not covered last Winter. Since the Winters here in Ga. are mostly cloudy I will add some supplemental lighting so that the plants can grow in the winter. There are some HIGH Lumen CFL on the market at this time. Any suggestions would be greatly appreciated. Hans