trg-s338 wrote:
I'm building a 4 x 8 foot greenhouse planter and would like to embed
an electrical heating system, some kind of grid/mesh in the soil.
Just need to keep the soil around 70 degrees. Accomplishing this with
the least use of electricity is a plus if possible. Is this something
I can build or salvage off of an existing system? I would appreciate
any suggestions or direction where I can research further. Thanks.

If this is an indoor system you can buy standard under-bed planter
heaters for this. Or you can go the lower tech route and use a water bed
heater.

Another option would be to go with a solar/water heater system.
I use a small water heater and used nylon tubing routed through sand,
then over the sand I have a layer of root stop fabric and then the
planting soil. The water heater is set under one end of the bench and
there is also a solar collector on the side of the greenhouse. I have a
thermostat control system that circulates the water through one or both
depending on temperature. For the months that it runs it costs about 75
bucks to keep the greenhouse and the planting beds warm.
--
Steve W.
Near Cooperstown, New York