[noshed]

My greenhouse is going from 4deg to 38 at the moment. I may be firing pottery come July

[Trillium]

Is that with or without glass whitewashing?
I notice over here that commercial greenhouses spread a black mesh with small holes over their roofs and it seems to help. It's strapped down to side clips to make it anti-wind proof.
Perhaps you should turn yours into a summer sauna room  

[ytyynycefn]

Mine got up to 46C today, and that was with the window, louvre and door wide open - and covered with shading paint  :shock:

Time to get out the Rokolene shading next  :?

[slow_worm]

My conservatory gets up to 52 deg C with windows and doors shut!!