What is recommended sq ft for this unit?

Typically for a unit a 75,000 BTU heater it is around 1,400 to 1,500 square feet. We do recommend using our Sizing Guide which will allow you to know exactly what kind of unit you'll be needing as there are many determining factors such as insulation quality, location, etc... If you have any further questions please feel free to give us a call! Thanks.