I’m zone 6 so year around might not be an option, but almost year around could be. I would like to get a big jump on seedlings for earlier and longer harvests. My father-in-law can get 55 gallon drums for free, and I’m wondering if I could use a couple of those filled with water to help heat at night.
They use drums filled with water as a heat reservoir all the time in greenhouses. I’ve never studied the temp variations to see what temps it will protect against. Lot’s of variables would come into play. The greenhouse I keep going all winter is only 6x8 so is relatively easy to keep heated. I can at least grow all the greens we need in there.