10 months ago
Last edited at 9:03PM on 2/17/2013
A South facing house in San Antonio, Texas with cathedral or vaulted ceilings will be almost identical in efficiency during the summer months assuming that the same type of energy efficient construction materials are used and the windows are similar in size, facing, and thermal value. Given the fact that hot air is lighter than cold air the air conditioned air will stay close to the floor where people need it to stay cool and the hot air will stay near the ceiling. In the winter the warm air will be needed near the floor not the ceiling so instead of trying to heat the entire space use reversable ceiling fans to recirculate the heated air that rose to the ceiling back down the walls to the floor where it's needed. That will entail the use of more electricity to operate the ceiling fans that is approximately the same for both ceiling styles.
I suppose that would depend On where the house is. Cathedral ceiling homes are harder to heat, Givin the limited amount of other detail you have provided I would speculate the home with an attic would be most efficient .
Cathedral ceilings can prove to be more energy efficient depending on a number of factors' including the angle or pitch of your roof. You have to select a design that will be most efficient for you. Consult with your designer or contractor before making your choice.