I've wondered about this for a while- since the sun in our hemisphere is to the south in the winter, does the north side of a GH need to be transparent? If the north wall is vertical, it would not shade the plants. Also, would a reflective surface on the north side have a positive effect on the plants? I would agree with some others that 55-gallon barrells do not seem to absorb much heat and warm the GH at night. We shall try milk jugs painted black. Do 5-gallon buckets need to have lids on them to work best?
Thanks in advance,
I asked a Science guy today about some of these issues. Wayne, he agrees with you about the north wall and reflection, and gave explanations. Lids on water containers are better than no lids. Gallon is better than 5-gallon. Last year two 55-gallon barrells I tried didn't help heat and he explained why. Double layers of plastic sheeting, not touching, do "change" our climate zones by several (3, I think I remember reading) zones, which mean we would benefit greatly. I am going to experiment with some different things, but won't truly know complete results, because I can't replicate all other conditions from hoophouse to hoophouse. It's fun learning about all of this stuff, and these forums put us in touch with people who have helped me a great deal.
Thanks to all,
I agree the 55 gallon barrels didn't work as well as my stacks of 5 gallon buckets, and it was much easier to handle them. Milk jugs are hard to stack but you can put them on your shelves near plants easier.