How many btu per square ft?

Thank you for your question. The answer is dependent upon several different factors. Firstly, it is dependent upon how well insulated your space is. The second is depednent upon which climate zone you reside in. In the warmer climate zones, you will need 30-35 BTU's per square foot for efficient heating. In colder climate zone you will need closer to 50-60 BTU's per square foot. For assistance in determing the right size system to meet your needs, please give us a call at 1-888-295-2009.