He only tracked it for two weeks, which is probably not a large enough sample size. I don't have anything growing in the dead of winter, either. I don't know if that affects the phenomenon. Also, I think it would only be relevant when growing just under a single layer of plastic, so if you did have low tunnels or hot boxes like he had, then it would not be a concern.
Humidity is great when it's cold, but not good when it is hot outside.
I think the best design for heating would be to heat water, and then circulate that water through the floor. Obviously that is a bit of an investment.
The best off-grid design I have seen is "active solar." A few panels run fans that blow hot air through pipes in a gravel floor during the day. At night, the fans reverse, and pull air up out of the warm gravel. That design outperforms "passive" solar, which is a typical unheated greenhouse with any mass in it. I have a thick gravel floor, which I think helps a lot to store heat, but I would do better with the active solar setup; I just didn't have the money to build it.
|