As presented in this chapter, beyond building smaller, key things to consider when trying to build energy-efficient houses include: As presented in this chapter, beyond building smaller, key things to consider when trying to build energy-efficient houses include: a. Insulation. b. Air tightness. c. The quality of the heating and cooling equipment. d. Water-saving devices. e. High quality windows and doors. f. All of the above g. A, B, C, and E