Wood fired hot tub to heat greenhouse? | Food Production and Preservation | Forums

So I'm sitting here looking at the snow daydreaming, thinking of a winter greenhouse, ways to heat without electricity,etc. Was perusing craiglslist at the same time and came across this hot tub for 300 bucks

seems would be a excellent heat sink to moderate cold temps at night and cloudy days, electricity bill would be to prohibitive, but what about converting it to wood fired, you would get the heat from the woodfiring, then the water would store the heat for overnights. Thoughts?