Energy-efficient designMIT researchers are helping architects optimize both design and energy efficiency.Nancy W. Stauffer | MIT Energy InitiativeJanuary 23, 2017SHARECOMMENTDesigning energy-efficient buildings can be challenging: Incorporating features that decrease the energy needed to run them often increases the energy-intensive materials required to build them, and vice versa. Now an MIT team has demonstrated a computer simulation that can help architects optimize their designs for both future operational energy and the initial energy required for making structural materials at the same time.The technique rapidly generates a set of designs that offer the best compromises between those two critical energy components. The architect can then make a choice based on quantitative information as well as aesthetic preference. The demonstration produced some striking results. In one case, choosing a design that was slightly less efficient in operational energy cut energy for structural materials in half an opportunity that would have gone undetected using a simulation that optimized operational energy alone.In recent years, concerns about global warming and greenhouse gas emissions have prompted efforts to make buildings more sustainable, or green. The main focus has been on reducing the energy that buildings require for heating, cooling, ventilation, and lighting. But an increasing role is being played by structural embodied energy, that is, the energy used to extract, process, and transport the structural materials in them.Newly constructed buildings have become so efficient to operate that the energy embodied in the materials required to create them is becoming a larger and larger percentage of the total energy used, says Caitlin Mueller, assistant professor of architecture and of civil and environmental engineering at MIT. Energy is embodied in building materials such as finishes, insulation, and cladding, but far more is in the buildings structural system. And while benefits from more energy-efficient operation are spread over the lifetime of the building, energy savings from reducing that structural embodied energy notably, by early decisions about a buildings overall shape are reaped immediately.When designing a building with energy in mind, therefore, architects need to consider both operational and structural embodied energy, and the two are intertwined. For example, extending the roof out beyond the edge of a building can shade windows and reduce cooling needs in hot climates, but making an overhang thats structurally sound can take a lot of energy-intensive material.The challenge is to determine a building design that trades off the two goals and also allows room for creativity and aesthetic decisions. Todays computer algorithms can help guide the design process, taking just seconds to generate designs that are optimized for several objectives at once. Even so, many architects and structural engineers persist in doing separate analyses, looking either to minimize operational energy consumption or to minimize the amount of energy-intensive material required. And in both cases, they tend to perform their analyses only after they have developed a conceptual design. They use a simulation program to see if the design theyve come up with is good enough, says Mueller a process she calls guess and check.The changing role of simulationMueller and her colleague Nathan Brown SMBT 16, now a