What is the difference between operational energy and embodied energy?

• A. Operational energy is used during building operation; embodied energy is for materials and construction
• B. Embodied energy is energy used during building operation; operational energy is for materials
• C. Both terms refer to energy used by occupants
• D. There is no difference; they are the same

Answer: (B)

The main distinction is when the energy is used. Operational energy is the energy needed to run the building during its life—heating, cooling, ventilation, lighting, hot water, and plug-in equipment. Embodied energy is the energy invested in making the building: extracting and processing materials, manufacturing components, transporting them to the site, and the construction itself. So one measures energy use during occupancy, the other measures energy invested before and during construction. For example, cement and steel require a lot of energy to produce, which becomes part of the building’s embodied energy, while the energy to heat and light the building once people start using it is operational energy. The option that reverses these roles isn’t correct because it confuses when the energy is consumed.