Green houses and greenhouse gases: Why exclusionary zoning is a climate catastrophe

Exclusionary zoning, a practice historically used to racially segregate communities, plagues issues across the political landscape, from climate change to education. This article is the last in a series on how exclusionary zoning perpetuates a discriminatory housing system that threatens our aging population, education system, and climate.

 

What is exclusionary zoning?

Exclusionary zoning is a policy that sets land use requirements, such as barring apartment buildings in a residential area or setting minimum lot sizes. In practice, it keeps certain residents (i.e. low-income residents and residents of color) from living in certain communities (i.e. wealthy and middle-class white communities) and keeps property values for homeowners high.

Today, local officials apply exclusionary zoning most often as a tool to constrain housing supply, restricting land use to low-density residential development — usually single-family housing. Zoning only for single-family housing is, by definition, exclusionary zoning. Because dedicating huge swaths of land to single-family housing is the central organizing principle of suburban planning, this article will focus especially on the environmental impact of the suburbs.

 

Why is exclusionary zoning critical to climate change?

One of the largest greenhouse gas-emitting industries in the United States is the residential building sector, depending on how output is measured. Looking only at upstream power generation — lighting, warming, and cooling homes, cooking, refrigerating, using appliances, and heating water — residential buildings constitute roughly six percent of total greenhouse gas emissions. When indirect emissions from off-site electricity are added, that figure rises to over 16%. And this is a conservative estimate; sizing the residential building sector’s true output would include the manufacturing of steel, cement, and glass, as well as transportation emissions from urban sprawl.

A deeper look at the data reveals suburban neighborhoods are the sector’s worst perpetrators. Depending on how “suburbs” are defined, the average suburban household produces up to twice the national household average. In large, populated urban areas, where denser forms of housing are more likely to be legal and vehicle ownership rates are lower, the typical home produces roughly 50% below that average.

When exclusionary zoning limits neighborhoods to large-lot, detached, single-family houses, governments create an energy inefficient mix of housing options and set the costly conditions for sprawl.

 

The building problem

Among the varieties of residential housing, single-family houses are by far the most environmentally destructive. The key is examining the difference between the average carbon dioxide emissions of single-family houses and denser kinds of housing — a Sasquatch-sized contrast in carbon footprints, made worse by the fact it’s illegal to develop anything other than single-family housing on approximately 75% of residential land in most American cities.

Single-family housing requires a deep pit of electricity consumption to heat and cool its environments. Multiplied on a neighborhood, city, or countywide scale, single-family clustering spawns a host of systemic emissions problems beyond this simple per-unit differential.

Compare northwest Washington, D.C. to nearby Great Falls, Virginia. Northwest Washington is no density mecca, but it has one of the most diverse housing mixes in the metro area. Its average household annually emits roughly 10 metric tons of carbon dioxide from housing energy use alone, and about 32 metric tons when accounting for transportation and other factors. In Great Falls — composed of 80 to 100% detached single-family housing, with no attached single-family units and just a smidgeon of multifamily — the average household annually produces 20 metric tons of carbon dioxide from housing energy use, and over 92 metric tons with transportation and other factors included. Higher income individuals tend to have more carbon-intensive consumer lifestyles, and Great Falls is a wealthy area, but housing stock still explains a large piece of the emissions story.

What about retrofitting the suburbs for greater energy efficiency rather than building new housing? The Intergovernmental Panel on Climate Change found the most thorough retrofits of detached, single-family houses decreased energy use by 50 to 75%. Yet energy-efficient, retrofitted single-family suburbs can’t compete with non-green multifamily homes, or with their urban single-family counterparts when transportation-related emissions are considered. To a large extent, the environmental virtues of multifamily housing come from the range of transportation modes available to its residents, and its proximity to shopping, work, and other destinations. Maximizing multifamily units’ value to sustainability and productivity means coordinating public transportation decisions alongside development choices to avoid creating dense but car-dependent islands.

Ultimately, green upgrades to single-family houses should be encouraged to move the needle, but they are no substitute for structural housing changes.

 

The transportation problem

The transportation sector, the largest emitting sector in the United States at 29% of total greenhouse gas emissions, is a more serious offender than the building or industrial sectors, and the problem is heating up. From 1990 to 2017, total vehicle miles traveled by passenger cars and light-duty trucks increased by nearly 46%, in part due to growing sprawl. To boot, buildings typically depend on energy from natural gas sources, yet most cars run on gasoline and diesel, which are far worse sources of greenhouse gas emissions. NASA called cars a bigger threat to the climate than heavy industry and manufacturing since cars don’t release aerosols to offset their warming effects.

Exclusionary zoning is endemic in both urban and suburban neighborhoods, but it packs an extra carbon punch in the suburbs due to sprawl’s transportation externalities. Low-density housing foments car-dependence as the distances between home and work, retail, recreation, and basic services increase. When it’s difficult or unsafe to walk, bike, or access public transportation, the built environment forces residents into their cars.

A study by the World Bank found sprawl to be a greater driver of transportation-related carbon dioxide emissions than either population or GDP growth. The problem is not growth in-and-of-itself, but growth outward rather than upward; many studies support the claim that increasing density decreases the need for driving. For example, researchers at University of Maryland found residents in dense places drive 25% less, even after controlling for socioeconomic differences.

What about electric cars? Unfortunately, national politicians are counterproductively deifying electric cars in their climate plans. Manufacturing electric cars is twice as energy-intensive as manufacturing combustion engine cars, and the former are only as green as the source of electricity that powers them. More importantly, a simple switch from combustion engine to electricity would likely further entrench the nonenvironmental costs of sprawl, including racial and socioeconomic inequity.

 

The path forward

A recent hearing of DC’s Historic Preservation Review Board yielded this comment from a board member: “I applaud your greenness and your desire to save the planet, and I realize that we are in a crisis politically as well as sustainably. But I just have this vision of a row of houses with solar panels on the front of them and it just — it upsets me.”

From buildings to transportation, there is no climate solution without addressing the zoning elephant in the room. That can’t happen if local government bodies can’t even stomach solar panels. To be sure, zoning problems differ from city to city, and each community must tailor their solutions to the unique transportation and economic needs of its residents, but the “hurricane” housing pattern of low-carbon urban cores ringed by high-carbon suburbs is common to metropolitan areas across the country. The problem is especially dire for the most populated metropolitan areas.

If municipalities won’t act, higher levels of government should step in, as Oregon and California recently have — the planet depends on it.

 

Photo by Jocelyn Erskine-Kellie on Flickr.

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Online Editor Devin Edwards is a Class of 2020 MPP candidate focusing on urban policy. He is from the beautiful state of Oregon, where he worked as a data analyst and volunteer teacher. At Georgetown, Devin researches wealth-building policies for the McCourt Policy Innovation Lab and hopes to continue advocating for inclusive and empowering urban design in the future, whether in the nonprofit space or local government.