I have the same problem. I put a max min thermometer in there a couple of days ago and despite the door and roof vent open, the temperature peaked at nearly 45C on Friday and reached just over 37C today, with minimums around 21C. Unfortunately my crops in there are not native to Death Valley California, so I have ordered some shade paint to spray on the south facing glazing. With the outside temperature dropping considerably from tomorrow and cloudier weather, the greenhouse temperature should moderate over the coming week.