growing in a basement that is about 50 degrees Fahrenheit I use an electric heater and have burnt my plants. I have tried to make a screen (plywood withe holes in it) to diffuse the heat so its not so direct onto the plants. Having the heater inside the space will always run the risk of overheating the plants. Heating the entire basement or room that the plants are in is optimal but expensive. there was a thread on here were a guy used dryer vent tubing with a small heater. the actually heater was outside the room but the heat was pumped in, i would think that the heat would eaither cool before getting into the grow space or just be hot and burn the plants anyway. either way its something to consider.
IS heating from the top or bottom better. Heat rises so i have my heater right at the bottom near the plants. But if i was to heat from the top down then i would not torch the plants.
They have some pretty cheap electric heaters at Wally World now as they are all on sale with spring coming. They are like 10-20 bucks with thermostat so they'll shut off when it reaches set temps. I put my heater on a timer for about 8 hours (4 hours off so it'll cool down to around 60-65F) during their dark period otherwise my room gets down to 50F which is too cold for my plants. I even have to have the heater on with the light on when it gets under 30F outside due to my strange setup but soon (I hope) the warmer weather will start so I can stop using the extra watt$.
that he ended up not using... he said due to noise... but his methods were very unsafe... you can do this.. but don't modify the heater the way he did.. unless you enjoy burnign your house down
Do what I did, I have my CFLs hanging close to the plants, and than one heat lamp that hangs a lot higher. I don't know if I'll keep it once the plant grows, but it keeps it warm but not too warm, in between 75 to 85 degrees