The message
from "michael adams" contains these words:

That assumes that the net radiation into the heap is positive - a VERY
debatable matter.

That isn't the issue.

If the brick walls are painted black they'll absorb solar
radiation rather than reflecting it straight back and warming
the surrounding atmospere. The warmer the brick walls are, the
less heat will pass from the heap into the walls, given that
less heat passes from a hot body to a warm body, than to a cool
body. And so less heat will be lost from the heap overall, as
result of paining the walls black - and more solar radiation
will be absorbed from day one, when the heap isn't actualy
generating any heat of its own.

Thank you for your helpful contribution, nevertheless.

I consider it a very helpful contribution and well-thught-out, and even
if you could arrange for the black face/faces to be presented to the sun
at right-angles to its elevation while it is playing on it/them, and the
heap is at a normal temperature (for compost heaps) the balace has to be
a net loss of heat.

I'll no doubt rejoin this later - England wants eleven runs to win - Oz
wants three wickets.

--
Rusty
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