Contemporary homes built with factory manufactured components generally enjoy a high efficiency rating from utility companies; air infiltration is minimized due to the engineering process.
Some manufacturers build "green" with its design and construction process that saves energy and natural resources by minimizing waste and recycling materials. At least one known manufacturing plant is Energy Star certified to build its components and certify them in the factory as Energy Star qualified, only then requiring a HERS rater on-site to finalize the certification. The factory process has less of a negative environmental impact on the home site. A "green" modular home uses less energy, water and natural resources.