This 8'x16' one is attached to the South face of the house, with double-glazed glass on the sides/door, and 7-layer corrugated polycarbonate on the roof (to protect from ice/snow falling off the house roof).
The foundation is concrete and brick, no insulation except under the floor below a couple of feet of sand. There are three large steel barrels, painted black and filled with water for extra heat ballast.
There are two automatic roof vents, but I wish we had also thought to specify a side vent on the far wall from the photograph above, so it could get cross ventilation with the exterior door (behind the camera).
No heat source other than the Sun, or when we leave the glass door open between it and the home. It is usable for starting/growing things here from early March through June, and from September through the end of November. In the main summer months it can be used for large pots of chillis and other HEAT loving things, but it does get very hot even with the door pinned wide open.