A new algorithm-based method of designing floor plans for apartment buildings could reduce greenhouse gas emissions by ensuring more efficient use of space, according to a new study.

Buildings account for 40% of greenhouse gas emissions, but until now most policies to encourage more sustainable construction have been focused on heating and cooling systems or building materials such as insulation and windows.

“These findings question the way we currently incentivize new construction or give tax breaks to ‘supposedly’ low-carbon buildings,” says study team member Ramon Weber, an architect at the University of California in Berkeley, who conducted the work as a graduate student at the Massachusetts Institute of Technology. That is, pack a McMansion full of insulation and stick a set of solar panels on the roof, and by current standards you’ve got yourself an environmental winner.

It’s well known that energy use in buildings is roughly proportional to building size, but there has been little attention to making apartments as small as possible while making sure they still function well for living.

“As an architect I find it very encouraging that we could prove that space matters,” Weber says. “For too long sustainability has been a question that we only try to solve with ‘technical’ means. I hope that my research contributes to emphasizing that spatially efficient designs are crucial for creating low carbon buildings.”

Making buildings more space-efficient would reduce greenhouse gas emissions associated with building operation to a greater degree than making changes to the building exterior in 72% of a sample of buildings in Zurich, Switzerland, 61% in New York, New York, and 33% in Singapore, Weber and his collaborators report in a paper published in the journal Nature Communications.

To demonstrate this, Weber and his collaborators turned to a newly developed tool called a “hypergraph,” which encodes floor plans as a collection of nodes and edges representing rooms and the connections between them.

“I was actually surprised how robust and scalable the method turned out,” says Weber. “I had surveyed different approaches and it became clear that we could not just use existing methods from computer science research to represent a floor plan. The hypergraph framework that I developed is specifically made for architectural design and building floor plans, and as such the first of its kind.”

The hypergraph can help researchers evaluate existing floor plans as well as automatically generate new floor plans to subdivide a given building footprint into apartments or to subdivide a given apartment unit into rooms.

A separate computer analysis ensures that the floor plans can accommodate all of the necessary furniture for a given room’s function (for example, a bed, dresser, and cabinet in a bedroom) while minimizing excess space.

The researchers also modeled the floor plans in three dimensions to analyze daylight and other aspects of comfort for people living in the apartments. The automatically generated floor plans increased apartments’ access to daylight by up to 24% in Zurich, the researchers report, suggesting that this strategy could make dwellings more pleasant to live in as well as more environmentally sound. (They found smaller improvements in access to daylight for buildings in New York and Singapore.)

In the future, Weber aims to expand his analysis from apartments to whole neighborhoods. “On a building scale we have to figure out what design decisions have the biggest carbon impact,” he adds. “For instance looking at a how building floor plans relate to a building’s structure and with it the carbon emissions from the materials used (the embodied carbon).”

Source: Weber R.E. et al. “A hypergraph model shows the carbon reduction potential of effective space use in housing.” Nature Communications 2024.

Image: AI-generated