In many homes, we find that there is ductwork in the attic, it is a logical spot to put the equipment. However, it is left subject to the extreme conditions of the environment. In the summer, the duct lines and the air in them heats up to the same sweltering temperature of the attic. When cold air is pumped through to try and cool the home, it is heated up by the duct lines and the hot air in them, making it more difficult to cool the home down. The reverse is true in the winter when the attic is the same temperature as it is outside.