Growing Greener
The Environmental Benefits of a Compact and Connected Boulder

Executive Summary

Boulder is known for being an environmentally conscious city. Boulder is surrounded by a ring of parks, open spaces and preserved land in the mountains. The city strives to promote water conservation and reduce personal vehicle travel and has ambitious climate goals.

However, Boulder’s positive contributions to the environment are undermined by housing policies that contribute to regional sprawl and increase global warming pollution.

Boulder has many policies in place that have caused housing to be scarce and expensive. For example, Boulder reserves most of its residentially zoned land for single-family homes, the least efficient type of housing.

By combining policies that encourage compact development, sustainable transportation and green building practices, Boulder can help to address global warming, improve the quality of our air and water, and protect Colorado’s undeveloped areas from sprawling development.

The inability of people who work in Boulder to find or afford housing in the city encourages long commutes that contribute to regional air pollution and global warming. Three out of five jobs in Boulder are held by people who live outside the city.

  • Inbound commuters drive about 29 miles roundtrip into Boulder each day on average and 77 percent are alone in their vehicles.
  • Nonresident commuters alone in their cars make up most of the vehicle traffic entering Boulder during the morning rush hour.
  • Boulder’s inbound commuters collectively drive up to 245 million more miles each year than they would if they were Boulder residents. This results in over 99,000 metric tons of additional carbon dioxide emissions each year – equivalent to putting over 21,000 more cars on the road.
  • Vehicle travel emits 31 percent of Boulder County’s nitrogen oxide (NOx) emissions and 24 percent of the county’s volatile organic compound (VOC) emissions, which react with one another to form ozone, which is at unsafe levels in Boulder County.

Enabling more people who work in Boulder to live in the city would allow them to drive less and walk, bike and take transit more, reducing air pollution and greenhouse gas emissions.

  • If one-third of Boulder’s nonresident employees moved into the city and drove as much as current residents, there would be up to 6,392 fewer vehicles on Boulder’s streets during commute times carrying only one passenger.
  • This would also prevent up to 81 million miles of driving each year, which would reduce greenhouse gas emissions by over 33,000 metric tons of carbon dioxide – equivalent to taking over 7,000 cars off the road. Those reductions would get Boulder over 10 percent of the way to its 2050 transportation climate goal.

Enabling more compact development, particularly along transit corridors like Broadway and near commercial centers, could further reduce driving and associated emissions within Boulder.

  • People drive less and walk, bike and use transit more in compact neighborhoods than in sprawling developments. For example, Boulder residents who live in detached single-family homes are nearly twice as likely to drive alone to work as those living in attached multi-family dwelling units, who are more likely to walk, bike or take transit.
  • Increasing the number of total housing units in Boulder’s most populous neighborhoods in North Boulder, South Boulder, Southeast Boulder and Gunbarrel by 15 to 30 percent, focusing this growth around existing transit corridors, and pairing it with mixed-use development, could trigger a large community-wide modal shift away from car-travel and toward the clean and efficient transportation alternatives the city already provides.
  • Boulder has many initiatives to minimize vehicle emissions by encouraging walking, biking, transit and electric vehicles, such as extensive networks of bike paths. Increasing infill development – the redevelopment of already developed land – would allow more Boulder residents to live close enough to jobs and recreation opportunities to walk or bike and take transit, helping to support infrastructure expansions and improvements.

Increasing compact development within Boulder would not only reduce driving and associated emissions, but also environmentally damaging sprawling development across the region. A wealth of evidence from dozens of studies by academics, government agencies and nonprofit organizations shows that compact development has less overall environmental impact than low-density development.

Compact development in Boulder would benefit the environment in many ways, including:

  • Reduced emissions: A 2011 U.S. Environmental Protection Agency (EPA) study found that shifting from conventional suburban development to compact, transit-oriented development is just as important as shifting to the most energy efficient building designs and fuel-efficient vehicles for reducing household energy use and emissions.
  • Land preservation: Housing more people within the already developed areas of Boulder can help reduce the development of regional open space, farmland and wildlands treasured by Boulder residents.
  • Healthier air: A study published in the Journal of Environmental Management in 2008 found that compact cities experience up to 62 percent fewer high ozone days than sprawling cities. This is crucial for Boulder County, which is in violation of federal air quality standards for ozone pollution. In 2018, there were 52 ozone action days in the Front Range region when residents were warned that exercising outdoors could harm their health.
  • Improved water quality: Compact residential development minimizes the amount of impervious surface cover, such as roads and buildings, in a watershed, resulting in less runoff pollution in the region. A 2009 study published in the Journal of the American Water Resources Association concludes that compact development may be “the single most important practice any city can undertake to improve the surrounding environment.”
  • Reduced flood risk: A multidisciplinary review of scientific literature published in the Journal of Urbanism in 2008 concluded that compact development patterns can mitigate the enhanced flood risk that comes with urban development.
  • Lower water consumption: In Boulder, residents who live in single-family homes use more than twice as much water as those who live in multi-family homes.

Increasing compact development can help Boulder to meet its goals to reduce greenhouse gas emissions, increase affordable housing availability and much more.

In 2015, Boulder drafted A Toolkit of Housing Options that could increase housing in the city, but has not implemented most of those suggestions. To create a more connected community with less environmental impact, Boulder should:

  • Re-zone areas to allow for more compact, mixed-use development – which incorporates homes, jobs and recreational opportunities – particularly along transit corridors and near commercial centers.
  • Encourage accessory dwelling units (ADUs), which are additional housing units within existing homes or on the same property, such as basement, attic, above-garage and detached, guest house apartments. Rented ADUs can provide a source of income for households – as well as assistance for aging households.
  • Increase home occupancy limits for unrelated people, which are currently three people in low-density residential areas and four people in medium- to high-density areas.
  • Consider parking maximums instead of parking minimums for homes and businesses and implement the parking principles from the city’s Access Management and Parking Strategy (AMPS).
  • Raise height limits for buildings in key locations, particularly along transit corridors and near commercial zones to the east of Folsom Street, and allow buildings above 35 feet in height but below 55 feet by right.

To enable new growth without additional traffic, Boulder should also:

  • Expand Boulder’s transportation demand management (TDM) programs like the EcoPass, parking cash-outs, carshare, and bikeshare programs, which encourage residents and employees to get around by means other than driving.

By increasing compact commercial and residential development, such as duplexes and low-rise apartment buildings, Boulder can create neighborhoods where homes, jobs and recreational opportunities coexist, connected by a transportation system that enables and encourages walking, biking, transit, shared modes of transportation and electric vehicles. By prioritizing infill development and maximizing the housing potential of existing buildings, Boulder can create a more compact community while preserving open spaces. These changes would reduce overall energy use and greenhouse gas emissions, land consumption, air and water pollution, flood risk and water consumption in the region.

Increasing compact development is a critical step for Boulder to take to tackle climate change and protect the environment.