In message , michael adams
writes

"Janet Baraclough" wrote in message
...
The message
from "michael adams" contains these words:


"Nick Maclaren" wrote in message
...
In article ,
michael adams wrote:

Painting the brick walls and wood panels black would allow them to
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

better absorb any heat - without reflecting it away unlike a paler
colour - while still insulating the pile against heat loss at
night and retaining any necessary moisture in the heap.

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.


You haven't ascertained from the OP whether the structure gets any
direct sun at all. Even if it does, since the structure is only 50 cm
high, it seems unlikely that such low walls will get enough sun on them
for long enough to affect the heat of the contents. Even less if only
one one of the short walls (1 m) faces the sun.


michael adams wrote:

Painting the brick walls and wood panels *black
^^^^^^^^^^^^^^^
*On top of the structure as specified by the OP.

hint:see above

It would appear you're attempting to outdo Mr McLaren
in nitpicking.

Thats 0 - 3 in my favour, thus far I believe.

Would you be aware that surfaces that are good at absorbing radiation
are also good at radiating energy? A black compost heat container will
indeed absorb more heat when in direct sunlight. At night, and perhaps
when shaded, it will lose more heat. Given that a compost heap generates
heat internally, and therefore is above the equilibrium temperature for
a passive object on the surface of the earth, at first sight it seems
that painting the heap container black will reduce the time averaged
temperature.

How significant this is depends on a number of factors. For a well
insulated heap, such as one with brick walls, and wooden covers, it may
be negligible.

With respect to the OP's question, replacing the wooden panels with
corrugated plastic presumably allows heat loss from convection via the
ends of the corrugations. I imagine that plastic is thinner than the
wood, which would contribute to it being a poorer insulator. If clear,
it will allow visible light to pass through and heat the surface of the
compost directly, while absorbing radiated infra-red light. My intuition
is that better insulation is more important than exploiting the
greenhouse effect.
--
Stewart Robert Hinsley