Before we replace a furnaces, we do a heat loss/heat gain assessment on your house To see how much it will lose in the winter. And how much it will gain in summer. When this is done it gives us information which we analyze your duct system to see How much air will flow though it at a reasonable velocity.With those calculations Complete,we can choose the equipment that is the best option for that house, and We can make informed recommendations on any necessary duct upgrades. We carry different furnaces with different models, warranties and qualities.