On 2 Oct 2004 05:18:01 -0700, (Dave) wrote:

I'm pondering what I might do to more efficiently heat my small
greenhouse to a minimal extent (40F). With the increase in the price
of natural gas I wonder if electric would be about the same? I also
want to consider assembling a table with a clear plastic cover to
contain the heat to a smaller area. Perhaps I could create a heated
table top? That would be useful next Spring. I suppose resistance wire
in a thin bed of sand?

Dave

For a fairly small area (3'xg') devoted to germinating seeds, I used
an aquarium heater in a tank of water with an aquarium pump to
circulate the water via plastic pipe embedded in sand. Worked OK as
long as I remembered to keep the reservoir topped up. That could be
cured with a float valve, but I didn't bother. Likewise, metal pipe
would transfer more heat.