My mother owns a 100+ year old home in northern Mississippi. It is approx. 2500 sf with 12 ft ceilings. The house sits 3 ft off ground on piers. She is considering installing central heat/air but wonders how that would work with the ceiling height. Any suggestions would be welcome and appreciated so that she can find the most efficient way to heat/cool the house. She is currently using propane heaters, as we are in the country, and window air conditioning.