David Woodbury

Hello, I have a 10'x10' greenhouse that I am moving some rain barrels into to help me heat the greenhouse.(Currently there is no heat) I was wondering If I was to put electric fish tank heaters into the barrels, would the cost of electricity be worth the amount of heat produced? I think I will also need a small fan to move the heat around the greenhouse. My goal is to keep the greenhouse above freezing.
Thank you!
DW

Hello, In all the food forest diagrams you see vines up in trees. I have a 25'-35' Doug fir in my yard I was thinking about growing hops up into and was wondering if anyone has tried this? I guess my question is, will the hops harm the growth of the Doug fir at all?
Thanks!