My first greenhouse was limited to 10x12', simply because it had to fit between the corner of the house and two AC units. I could have built one twice as large when I decided to add the second one, but because I thought it would be more aesthetic to have them the same size, with a stone walkway in between, I built another 10x12', but went with another design and another GH company. Oh, how many times have I kicked myself for this aesthetic delusion?
I wish I had built a16x24'. Keep in mind, the main thing is the square footage and cubic footage. The 10x12' has 120 sf. and 960 cf. A 16x24' has 484 sf. and 4,810 cf.