I made a box to grow peppers in the basement. Ambient temperature is about 60F. I use a 200 Watt air heater controlled by a baseboard heater thermostat. (It directly switches the AC current on and off). I set the controller to turn off the heater at 85F. I run the heater and 6500K fluorescent lighting 16 hours per day, then allow it to cool to ambient temperatures at night.
This is the same apparatus that I use to do germination testing. The box is lined with aluminum foil to make the most use of the lighting.
