I am an owner in an industrial real estate company. We own several large buildings that have large open spaces 50,000 - 100,000 sft with 30' and sometimes 40' ceiling heights. Some of our buildings are on propane because natural gas isn't available there. Can anyone steer me to a manufacturer to a product that will heat these spaces? We are open to hot air or hot water, with a preference for air. We are in Pennsylvania. Thanks in advance!