Garage heat

I had a house I was renting so I really didn't want to spend much money on the garage. So I stapled plastic on the ceiling and stapled cardboard (old boxes FREE ) between the 2x4's and the outside walls. Would have been great to plastic the walls also. It did make a nice difference. But I would suggest if using the kerosene torpedo heater to leave 1 to 2 square feet open in the ceiling for some venting.