Our 3 bedroom house (2250 sq. ft, 10ft and 8ft ceilings in bedrooms)has central air conditioning, but in the front bedroom (southwest exposure, Houston area), it will never get cool, except when the front bedroom window is open. A ceiling fan does not do much good to cool off the room. I believe this proves a problem with return air (door is mostly closed, teenager's room). Question I have is, can I add my own return air grille, and tie ductwork into the main return air duct in the attic to resolve this problem without affecting the rest of the home's air circulation?