That's a clever idea to use the heat tubes. Great way to preserve warmth for those cold nights and extending your season. I love growing larger watermelon but only get a couple because of the shorter northern growing season. That's where the green house would really come in handy. I really should brain-storm to come up with something for next year.
Thanks!
If you have a shed or garage with a south facing wall, you could always build a lean to greenhouse onto that, or the side of the house even. A stand alone greenhouse is a bit more work to build, but it depends on how big you want it to be.
YES! That's exactly what I was thinking.....a lean to on the back of the house. That would be awesome.