A new study confirms the obvious: big houses have bigger footprints. But wait, there’s more. By Lloyd Alter, Treehugger, July 21, 2020
The conclusion of a new study – The carbon footprint of household energy use in the United States – that everyone is focusing on would seem obvious: “Wealthier Americans have per capita footprints ∼25% higher than those of lower-income residents, primarily due to larger homes.” It doesn’t even sound like that much. But in fact, when you dig into this study, the issue gets more complex and more discouraging. Lead author Benjamin Goldstein summarizes in a press release:
Although houses are becoming more energy-efficient, U.S. household energy use and related greenhouse gas emissions are not shrinking, and this lack of progress undermines the substantial emissions reductions needed to mitigate climate change.
Household energy use is increasing as houses continue to get bigger and also due to “demographic trends, expanding use of information technologies, electricity prices and other demand drivers.” According to the study (my emphasis):
This lack of progress undermines the substantial emission reductions needed to mitigate climate change. The average lifespan of an American home is about 40 years (scrape-offs of older homes to build larger, newer ones with more bathrooms, etc), which poses challenges given the need to rapidly decarbonize. This makes decisions during design and construction, such as size, heating systems, building materials, and housing type, crucial. In the United States, a confluence of post-World War II policies helped move a majority of the population into sprawling, suburban households with energy consumption and attendant GHGs well above the global average. Without decisive action, there will be a “carbon lock-in” for these homes for decades to come.
Carbon lock-in is a problem that has been discussed in the green building community for some time; it’s the reason that incremental improvements in building efficiency are short-sighted and why we have to electrify everything right now. If you build a marginally better house and heat it with gas, you are locking that gas consumption and carbon footprint for the life of the house. But if you build to a much higher standard, say Passive House levels of efficiency, a little electric air-source heat pump can heat and cool. But there is no incentive to change when gas is so cheap, so every home built today locks in those carbon emissions. As the study authors note, this requires attacks on all fronts.
Residential energy emissions arise from a combination of economic, urban design, and infrastructural forces. Our exploratory scenario-based models indicate that meaningful reductions to residential emissions will require concurrent grid decarbonization, energy retrofits, and reduced in-home fuel use. Scenarios also suggest that making new construction low-carbon will require smaller homes, which can be promoted through denser settlement patterns. These results have implications for both the United States and other nations.
The study used tax assessment data to estimate the greenhouse gas emissions of 93 million houses, about 78% of the US housing stock, and found that the average home consumed 147 kilowatt-hours per square meter (kWh/m2). Not surprisingly, rich people had more square meters, more floor area per capita, and more emissions; “Despite variations in climates, grid mixes, and building characteristics across our sample, income positively correlates with both per capita residential energy use and related GHGs.” Extremely wealthy and sprawly neighborhoods approached 15 times the emissions per capita than denser urban areas.
Just a Few Practical Interventions Needed
The “practical interventions” needed to reduce emissions are “1) reducing fossil use in homes and in electricity generation (decarbonization) and 2) using home retrofits to cut energy demand and in-home fuel use.” The study authors call for more renewable energy and less coal, and “deep” energy retrofits to reduce heating, cooling, and lighting loads.
The authors get into controversial territory with their discussion of floor area per capita (FAC), calling for a reduction in the size of homes. “Meeting the 2050 Paris target also requires fundamental changes to the built form of communities. New homes will need to be smaller.” Housing also has to be denser and zoning rules have to change.
Increasing population density places downward pressure on FAC due to space constraints, land prices, and other factors. Zoning for denser settlement patterns better incentivizes smaller homes with reduced energy demands than single-family homes on large lots.
Low-Carbon Homes do not Necessarily Make for Low-Carbon Communities
The authors call for a Goldilocks, or missing middle density, of about 5,000 people per square kilometer. “If built using small plots and high building footprint ratio, this density is achievable through a mix of small apartment buildings and modest single-family homes.” They note also that even this density is at the low end of what is required to support public transit. “Thus, low-carbon homes do not necessarily make for low-carbon communities. Higher densities (and mixed-use development) are likely needed to confer appreciable spillover effects, such as increased low-carbon transport and related economic, health, and social benefits.”
In fact, the shopping list of changes necessary to build low carbon communities is extensive:
- Decarbonize the electricity supply.
- Tax incentives and preferential lending mechanisms for deep energy retrofits.
- Update zoning bylaws that favor suburban development.
- Use greenbelts to limit suburban sprawl. And,
- “Planners should exploit natural synergies between density, public transport, and energy infrastructure (e.g., district heating) when building these communities.”
But hey, this is no big deal:
All these measures need to happen in concert. Although ambitious, the form of the current US housing stock is not only the outcome of consumer preferences, but also policies enacted since the 1950s that led to coordinated action across sectors (e.g., financial, construction, transport) and scales (individual, municipal, state, and national) Similarly, a burst of large-scale projects by the Public Works Association (e.g., Hoover Dam) as part of the New Deal in the 1930s and 1940s fundamentally shaped the structure of US power sector. Given this history, it is conceivable that a concentrated effort could enable the US residential sector to meet Paris Agreement targets.
All we have to do to solve this is to have a New-Deal-meets-The-Manhattan-Project scale reinvention of the entire urban planning and development sector along with the entire housing industry. And we have to do it tomorrow because every housing unit we build now that isn’t an apartment built to Passive House standards is just adding to the carbon lock-in problem. Not a big deal at all!
Everyone writing about this study has concentrated on the finding that rich people’s houses have bigger emissions, which really shouldn’t be a surprise to anyone. Nobody seems to be talking much about the prescription the authors suggest for solving the problem, because they would have to face the fact that Benjamin Goldstein and his co-authors are correct:
We have to electrify everything, we have to fix everything we’ve already built, everything we build new has to be better and denser, and we have to do it all right now.
A Boulder County zip code produced the nation’s most greenhouse gas per person, study says
The zip code that produced the most greenhouse gas per person was in the mountains of western Boulder County, where the 23,811 pounds per person is 18 times higher than in the San Francisco zip code JUL 21, 2020
By Seth Borenstein, The Associated Press
Rich Americans produce nearly 25% more heat-trapping gases than poorer people at home, according to a comprehensive study of U.S. residential carbon footprints. Scientists studied 93 million housing units in the nation to analyze how much greenhouse gases are being spewed in different locations and by income, according to a study published Monday in the Proceedings of the National Academy of Sciences. Residential carbon emissions comprise close to one-fifth of global warming gases emitted by the burning of coal, oil and natural gas.
Using federal definitions of income level, the study found that energy use by the average higher income person’s home puts out 6,482 pounds of greenhouse gases a year. For a person in the lower income level, the amount is 5,225 pounds, the study calculated.
“The numbers don’t lie. They show that (with) people who are wealthier generally, there’s a tendency for their houses to be bigger and their greenhouse gas emissions tend to be higher,” said study lead author Benjamin Goldstein, an environmental scientist at the University of Michigan. “There seems to be a small group of people that are inflicting most of the damage to be honest.”
In Beverly Hills, the average person puts four times as much heat-trapping gases into the air as someone living in South Central Los Angeles, where incomes are only a small fraction as much. Similarly, in Massachusetts, the average person in wealthy Sudbury spews 9,700 pounds of greenhouse gases into the air each year, while the average person in the much poorer Dorchester neighborhood in Boston puts out 2,227 pounds a year.
“That is the key message about emissions patterns,” said University of California San Diego climate policy professor David Victor, who wasn’t part of the study. “I think it raises fundamental justice questions in a society that has huge income inequality.”
Even though richer Americans produce more heat-trapping gases, “the poor are more exposed to the dangers of the climate crisis, like heat waves, more likely to have chronic medical problems that make them more at risk to be hospitalized or die once exposed to heat, and often lack the resources to protect themselves or access health care,” said Dr. Renee Salas, a Boston emergency room physician and Harvard climate health researcher who wasn’t part of the study.
Salas and Sacoby Wilson, a professor of environmental health and epidemiology at the University of Maryland, who also wasn’t part of the study, pointed to studies in Baltimore and other cities showing that because of fewer trees, more asphalt and other issues, temperatures can be more than 10 degrees hotter in poorer neighborhoods.
“Heat waves are hell for the poor,” Wilson said.
Goldstein calculated the emission figures by crunching data on 78% of the housing units in America as of 2015, factoring the home’s age, size, heating supply, weather, electricity source and more. He then compared income levels.
Nine of the 10 states that produce the most heat-trapping gas per person rely heavily on coal or have cold weather. West Virginia by far leads the nation with 10,046 pounds of greenhouse gas per person per year, followed by Oklahoma, Wyoming, North Dakota, Kentucky, Missouri, Iowa, Alabama, South Dakota and Colorado.
California by far is the greenest state with 2,715 pounds of greenhouse gas per person. Oregon, New York, Utah, Washington, Rhode Island, Massachusetts, Idaho, Connecticut and New Mexico round out the 10 cleanest states.
The study’s 25 cleanest zip codes for residential greenhouse gas emissions are all in California and New York. The cleanest was Mission Bay in San Francisco, a white collar area with relatively new housing stock, where the average person produces only 1,320 pounds a year.
The zip codes that produced the most gas are scattered across Colorado, North Carolina, Pennsylvania, Alabama, Louisiana, Wyoming, Maryland, West Virginia, Minnesota, Missouri, Georgia, Arkansas, Indiana and Utah. The zip code that produced the most greenhouse gas per person was in the mountains of western Boulder County, where the 23,811 pounds per person is 18 times higher than in the San Francisco zip code.
Because some zip codes didn’t have adequate data, Goldstein said there may be additional zip codes at the extremes of the emissions spectrum. Also, he said some zip codes with smaller, expensive, energy-efficient apartments buck the national trend of greater emissions in wealthy areas.
Wesleyan University climate economist Gary Yohe, who wasn’t part of the study, said Goldstein’s analysis helps the search for solutions to global warming by offering “two new targets for policy action or behavioral modification beyond the usual list: floor space and density.”
But residential carbon emissions are harder to change than those from transportation, where you can trade a gas-guzzler for a cleaner electric vehicle, Goldstein said.
Noting that many residents are stuck with the fossil fuel-based energy delivered by their local utility, he said, “I don’t think we can solve this based on personal choices. We need large scale structural transitions of our energy infrastructure.”