Nice work, I did similar with Garage door steel panelling. I used 4 sections of Sectional Door sections then over lay them with Roller door panelling, similar to corrugated sheeting.
Image showing the Sectional Door Panelling.
http://www.iceinspace.com.au/forum/a...chmentid=88444
Image showing the Roller door Panelling.
http://www.iceinspace.com.au/forum/a...chmentid=88732
It is very cool in there even on a 40 degree day, it's almost as cool as inside the house. The white roof Helps a great deal. To add to it, I added white side skirts on the side to help reduce heat buildup on the sides, not sure if it is doing anything, but looks better...
http://www.iceinspace.com.au/forum/a...chmentid=98964
Pretty rough looking there, but I have since added capping around the sharp bits...