brick floor and black water drums to store thermal mass; I'm
wondering if anyone has found a better material to store the water
in, for example rectangular so there's not as much heat loss between
the barrels?
to my understanding you want the thermal mass to 'loose heat' - this
is what keeps the temperature up in your greenhouse. if heat is just
stored but not relesed into the surroundings (inside the greenhouse),
they are no good anyways.