Software tool could help architects design efficient buildings | MIT News


Typically, when architects or engineers design a new building, it is only at the end of the process, if ever, that a life cycle analysis of the environmental impact of the building is carried out. And by then, it may be too late to make meaningful changes. Now, a faster and easier system for performing such analyzes could change all that, making analysis an integral part of the design process from the start.

The new process, described in the journal Building and Environment in a paper by MIT researchers Jeremy Gregory, Franz-Josef Ulm, and Randolph Kirchain, and recent graduate Joshua Hester PhD ’18, is simple enough to integrate into software already used by building designers so that it becomes a seamless addition to their design process.

Life Cycle Assessment, known as LCA, is a process of examining all materials; design elements; location and orientation; heating, cooling and other energy systems; and the intended eventual disposal of a building, in terms of cost, environmental impacts, or both. Ulm, professor of civil and environmental engineering and director of MIT’s Concrete Sustainability Hub (CSH), explains that LCA is typically applied “only when a building is fully designed, so it’s more of a post-construction tool. mortem but not a real design tool”. .” This is what the team set out to fix.

“We wanted to find a way to bridge that gap between using LCA at the end of the process and getting architects and engineers to use it as a design tool,” he says. The big question was whether it would be possible to incorporate LCA assessments into the design process without it imposing too many restrictions on design choices, thus making it unappealing to building designers. Ulm wondered, “To what extent does LCA limit design flexibility?”

Measuring freedom of design

To systematically answer this question, the team had to come up with a process for measuring the flexibility of design choices in a quantitative way. They settled on a measure they call “entropy”, analogous to the use of this term in physics. In physics, a system with greater entropy is “hotter”, its molecules moving rapidly. In the team’s use of the term, higher entropy represents a greater variety of choices available at any given time, while lower entropy represents a narrower range of choices.

To the researchers’ surprise, they found that using their LCA system had very little impact on narrowing the range of design choices. “This is the most remarkable result,” says Ulm. When introducing LCA in the early stages of the design process, “you barely touch design flexibility,” he says. “I was convinced that we would reach a compromise,” where design flexibility would have to be limited in order to achieve better performance throughout the life cycle, says Ulm. “But actually the results proved me wrong.”

The system examines the full range of climate impacts of a new structure, including all three phases: construction, including consideration of embodied energy in all materials used in the building; the operation of the building, including all sources of energy necessary to provide heating, air conditioning and electrical service; and the final dismantling and disposal, or reassignment of the structure, at the end of its service.

Assessing the lifecycle impact of design choices requires consideration of a wide range of factors. These include: the climate of the location (for their research, they chose Arizona and New England as two very different cases of the American climate); the dimensions and orientation of the building; the ratio of walls to windows on either side; the materials used for the walls, foundations and roof; the type of heating and cooling systems used; etc As each of these factors is decided upon, the range of possibilities for the building becomes narrower and narrower – but not much narrower than in any conventional design process.

At any given time, the program “would also provide information about many things that are not yet defined,” essentially offering a menu of choices that could lead to more environmentally friendly design, says Kirchain, a principal investigator at MIT and co-director of the CSH, who supported the project.

Although designed specifically to reduce a building’s climate impact, the same tool could also be used to optimize a building for other criteria, such as simply to minimize costs, the researchers say.

Arrive early

Thinking about questions such as the ultimate fate of a building at the end of its functional life tends “not to be in the same order of interest for the design architect, when first working on a design,” versus more immediate factors such as what the building will look like to the client and meeting any particular functional requirements of the structure, Ulm says. But if new LCA tools are integrated directly into the design software they use, then insights into how a given design choice might affect the outcome would be constantly available and able to easily influence choices, even in ways subtle and subtle at the beginning of the process.

By comparing the design process with and without the use of such tools, the researchers found that the overall greenhouse gas emissions associated with a building could be reduced by 75% “without reducing the flexibility of the design process. “, explains Ulm.

Ulm compares it to gym metrics that provide information on the number of calories burned at any time during an exercise regimen, providing a constant incentive to improve results – without ever prescribing which exercises the person should do. or how to do them.

While the program is currently designed to assess relatively simple single-family homes — which make up the vast majority of living space in the United States — the team hopes to expand it to be able to work on much larger residential or commercial buildings as well.

At this point, the software designed by the team is a standalone package, so “one of our tasks going forward is to make it a plug-in for some of the software tools that exist” for architectural design, says Kirchain. .

While there are many software tools available to help assess a building’s environmental impact, says Kirchain, “we don’t see many architects using these tools.” But that’s partly because these tend to be too prescriptive, he says, pointing to optimal design and restricting the designer’s choices. “Our theory is that no designer wants to be told this is how design should be. Their role is to design without undue constraints,” he says.


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