I'm in zone 8 southeast Virginia and am looking for a way to overwinter some marginal to tropical potted plants. I don't need them to stay green neccessarily, just alive! Last winter I set up a pvc-frame, 6mil plastic covered greenhouse with some large bubblewrap draped inside. It was placed on a brick patio facing south and protected on all other sides by walls. I also placed some bagged mulch around the exterior to try and prevent drafts getting under the plastic. While it heated way up during the day, unfortunately it still dropped down close to the outdoor temperature at night.

So, this winter I want to try improvements. I assume I'll need some sort of heater and fan setup. Will a spaceheater style convection heater work or do I need something else that isn't bothered by the humidity? Or is there a cheaper/better method?

How can I best seal the bubble wrap to the plastic wall? This past winter it mostly ended up draped along the frame when the tape I used failed.

Would dumping mulch around the exterior seal it better than the bags, or do I need some other approach altogether?

Any other obvious improvements?

I appreciate any advice. Thanks!

Justin