This is me standing on top of an interior wall in an attic. Notice the "gap" on either side of the top plate of the wall? This wall had about 1/8" on each side. If you figure about 200 linear feet of interior wall with an average 1/8" gap on each side, that gives you a total of about 50 square inches of air leakage to loose heated/cooled air. There is a reason that new home builders are sealing the top wall plates of a home with foam now! ENERGY WASTE! Have us evaluate your walls to see if they are wasting your energy!