Which generates more greenhouse gases, transportation or buildings?

It all comes back to buildings.

A few months ago I wrote that Transportation is now the biggest source of US CO2 emissions, noting that the switch from coal to natural gas for power generation had caused emissions from power generation to decrease while cars kept turning into trucks and emitting more. More recently, the Rhodium Group released Final US emissions numbers for 2017, including other sectors, like industry and buildings.

© Rhodium Group

Architect Gregory Duncan saw this graph and suggested that architects and others in the industry should not get complacent just because the yellow line was so low, way lower than power or transportation.

"Of course, buildings affect emissions from power and transportation sectors as well. We in the AEC industry shouldn't assume that the yellow line being the smallest means that we don't have a big impact."

Lawrence Livermore National Laboratory and the Department of Energy/Public Domain

Indeed; I discovered that I was wrong when I said transportation was the biggest source of CO2 emissions when I was preparing a lecture for my Sustainable Design class at Ryerson University School of Interior Design, and discussed energy flows, were the power actually went, using what I have called The Chart That Explains Everything. Basically, most of the power goes into buildings, for light and mostly air conditioning.

© World Resources Institute

This graph from the World Resources Institute shows it more clearly by identifying the end use activities. Residential and Commercial buildings together account for 27.3 percent of carbon emissions from electricity, heating and other fuel combustion. And that is not even including the iron and steel and cement that goes into buildings, a big chunk of the 4.5 percent they put out.

© Alex Wilson/ BuildingGreen

Then there is the Transportation Energy Intensity of all those buildings- what Alex Wilson of BuildingGreen defined as..

...the amount of energy associated with getting people to and from that building, whether they are commuters, shoppers, vendors, or homeowners. The transportation energy intensity of buildings has a lot to do with location. An urban office building that workers can reach by public transit or a hardware store in a dense town center will likely have a significantly lower transportation energy intensity than a suburban office park or a retail establishment in a suburban strip mall.

He calculated that commuting used 30 percent more energy than the building itself.

Average Annual Person Miles and Person Trips per Household by Trip Purpose/Public Domain

Looking at data from the Federal Highway Administration, it was surprising how many person-miles were devoted to social and recreational. But how many of those trips are a function of urban design, the way our cities and suburbs are laid out. Ralph Buehler wrote in Citylab about how the US is designed for driving, and we do:

In 2010, Americans drove for 85 percent of their daily trips, compared to car trip shares of 50 to 65 percent in Europe. Longer trip distances only partially explain the difference. Roughly 30 percent of daily trips are shorter than a mile on either side of the Atlantic. But of those under one-mile trips, Americans drove almost 70 percent of the time, while Europeans made 70 percent of their short trips by bicycle, foot, or public transportation.

A residential street in Berlin/ Lloyd Alter/CC BY 2.0

In Europe, people often live in apartment buildings with offices and stores on the ground floors, so they do not have to drive to get dinner. In North America, it is zoning and urban design that makes it difficult and inconvenient not to drive.

So I cannot determine exactly what percentage of transportation emissions are directly attributable to buildings and urban design, but it's got to be well over half. And then of course, there is the concrete and steel for roads and bridges, the chemicals, aluminum and steel that goes into making cars. When you total it all up, probably most of our emissions are caused either by our buildings or driving to them.

Perhaps I am naive, but I keep thinking that if we built walkable and cyclable cities out of radically efficient buildings, we wouldn't be having these problems.

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