Yah 12’x16’ sounds right, its large and has my veggie raised beds in it. I have an asparagus crop i’ve grown from seed that’ll be hitting the three year mark this winter, so excited for that :). I have a 8’x14’ as well that has my citrus trees in it. After 3-4 years they have held up well. Yah that is a nice looking greenhouse, but wouldn’t you get a lot of mold in there below the half wood wall where the sun doesn’t shine in?
Yah lots to think about when getting one. I added sprinklers in to mine tied to the well so watering could be automated. Its been a lot of fun :)