Adding a heat exchanger to the gas furnace in the calving barn reduces expenses for John James of Redfield, S.D. To capture the heat that would be lost through the furnace’s ventilation system, a heat exchanger was built with 1.5-inch pipe welded into a 30-by-30-inch tube. A fan was mounted on one side to blow through the pipes. Mr. James notes that the intake and outgoing ventilation pipes are offset to increase flow around the pipes.