My niece put an addition onto her house and no way to put in heat/air conditioning from the main part of the house, so she got one of those units like is in a motel room - that is a heater and an air conditioner. She got a rebate from the local electric company. She only used it when somebody was staying in the new addition and said it did a really good job. But, you would have to have your new building wired for something that big. HTH