outdoor cold room

I want to install an outdoor cold room for meat up to 10 m2 ... specifically I would like to ask:1) what is better to put in the outdoor cold rooms? Panel or building materials such as concrete and brick? And which of the 2 cases is more economical?2) what is the best insulation?3) what refrigerant is most commonly used for cold rooms?4) insulation for floor and ceiling? How will I calculate what thickness of insulation I need and how will I calculate the thickness of the walls, whether it is a panel or a wall made of building materials?

Can I convert existing machines or do I have to buy new ones?

GOOD EVENING, we are active in the HORECA industry. I'm interested in reducing the energy efficiency of refrigerants. Can I convert existing machines or do I have to buy new ones?