I will be insulating the top ~1.5 ft. that is above the foundation to R-15 but the cement block foundation walls will not be insulated until the basement is finished sometime in the future. For now, this area will only be used for laundry and storage but will be a play room in the future. I received a proposal for a 12000 btu unit but from what I’ve seen from online calculators, this may be too little. Any advise would be appreciated. Thank you.