Blank canvas, steel sided 40x60 pole barn. Thoughts on insulating, electrical, heating???

I'm helping a friend with his new building and he went with heat in the floor but he is using a waste oil furnace to heat the fluid that runs through the floor. So if you have clean waste oil or transmission fluid you can burn that and it works great. And can cut down on energy cost as well. We use a 25000 btu heater to heat my 7 bay shop and machine shop. We burn about 3000 gallons of waste oil a season. But the oil is free.