Hello if it's the tube type it can be mounted on the side walk of the green house,if it's like a space heater free stand it in the middle of the floor near the door so that any draughts are warmed as they come in and rise up,last green house heater I used was 6feet long 30 inch wide,500,000 btu hung from the greenhouse roof and drank 250 gallons of 32 second burning oil in 10 hours when it had a tantrum jezza