A team of scientists from the Department of Energy's Oak Ridge National Laboratory and the University of Florida has developed a novel method that could yield lower-cost, higher-efficiency systems for water heating in residential buildings.The theory behind the newly termed "semi-open" natural gas-fired design, explained in an ORNL-led paper published in Renewable Energy: An International Journal, reduces the cost and complexity of traditional closed gas-fired systems by streamlining, and even eliminating, certain components.