Improperly sized or designed ductwork is the most common reason people are not comfortable in their own homes. Imagine for a moment that your furnace is your lungs. Now imagine that you are running a 1-mile race. If you are in good shape you should have no problem. Now imagine that you have to run that same 1-mile race breathing through a cocktail straw. No matter how good of shape you are in, you will never run the race as fast and easily as if you could breath normally. This inability to breathe is what happens when your furnace is forced to operate through improperly sized ductwork.