I built one that's 18x21'. It can produce more than double what the garden does. I opted for a woven poly fabric material due to price, but think glass would be the best way to go if you have money to spend. I think using scavenged and recycled material just makes sense. I have about four hundred in mine, which makes producing veggies cost effective. I've seen really nice units cost more than 10 grand, so it's kind of hard to justify how much your tomatoes cost there.