A couple of years ago we built the greenhouse. Its 15 square meters, the largest size you can build without special permissions. I would loved to made it a little bigger but it will do for us.
Its sunken in to the ground by about 50 centimeters. This gives the greenhouse a more stable climate.
We are going to do some inovative heating sollutions in the near future to the greenhouse but right now we dont heat it.
You can watch more about the greenhouse in these playlists on Youtube.