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January 22, 2021

Green Zoning: Accelerating Smart Growth in Single Family Zones

Green Zoning: Accelerating Smart Growth in Single Family Zones

[Editor’s Note: This article was originally published as part of the 2019 NAPHN Policy Resource Guide, release at its 2019 conference. Registration for this year’s NAPHN conference, PASSIVE HOUSE 2020, opens March 2.]

“How can cities that have green building codes have zoning bylaws that protect low-density single family housing?” – Lloyd Alter, TreeHugger

For a post-carbon, all-renewable energy future, we must expand decarbonization and GHG reduction to entire neighborhoods, cities and regions, unlocking the hidden potential of what Lloyd Alter has called ‘Green Zoning’. It is not enough to build high-performance green buildings, if they are dispersed through an unsustainable land use pattern.

Green Zoning Strategies

Advocating for land use policies that tilt the scale toward more compact and sustainable ways of living—green zoning—is critical to addressing our changing climate. Green zoning isn’t one size fits all. Based on the land use pattern and density, there are many strategies that can be used to make a given neighborhood more sustainable.

Policy makers, planners and building professionals should be advocating for land use policies that increase residential density, given the impact of these policies on carbon emissions. A recent study has shown that doubling population-weighted density has a massive impact, up to 18%, on CO2 emissions linked to transportation and residential energy use. At first blush, doubling residential density sounds like a radical idea or heavy political lift, but we need only look into the recent past, before the automobile and zoning made detached single-family houses ubiquitous. Here are some strategies to find space to share the land we’ve already zoned for residential uses in order to leverage the environmental benefits of smart growth fundamentals.

Welcoming ‘Missing Middle’ Housing

Many of the most desirable neighborhoods were built before zoning and contain both higher density and more housing options, and are generally more walkable. Originally laid out around carriages and streetcars, these neighborhoods often include a mix of rowhomes, stacked flats, duplexes and triplexes, and courtyard apartments, coexisting with more recent detached single-family houses. Dan Parolek of Opticos Design coined a term for the kind of small-scale, multiple household structures that have been nearly zoned out of existence—the ‘Missing Middle.’

Small-scale multifamily buildings are usually hidden in plain sight in former streetcar neighborhoods among single-family homes and can provide powerful narratives about the value of a diverse neighborhood character. Using a walkshed around neighborhood centers, land use policy shifts to distribute Missing Middle housing throughout established neighborhoods make shorter commutes, allow for more biking and walking, and leverage the energy efficiency of new high-performance buildings.

Making Single Family Lots More ‘Plexible’

As cities developed, many have done so inequitably, unevenly and unsustainably. Several U.S. cities have initiated long-range planning efforts to rebalance and distribute growth with an eye not only to climate challenges, but also to social benefits and economic vitality. The centerpiece of these efforts has been to incentivize the addition of more households per parcel in urban areas—making them more ‘plexible’. Sharing desirable urban residential land among multiple new households by creating more compact buildings, preferably along transit routes, and supporting different ways of community living, such as co-housing, all contribute to a more sustainable land use pattern.

The Minneapolis 2040 Comprehensive Plan, passed in 2018, looked at each part of the city and figured how to add innovative housing options within the existing city fabric. The most far-reaching and controversial aspect of the plan allows triplexes on any formerly single-family parcel as a baseline. The Minneapolis 2040 Comprehensive Plan increases housing supply and choice by allowing more multifamily housing along public transit routes and near METRO stations—traditional Transit Oriented Development—and in neighborhood interiors that already contain a mix of housing types. In most cases more households can be accommodated in structures that fit within the already acceptable single-family volume envelopes. The plan supports “innovative, energy efficient, and creative housing options, such as multi-generational housing that supports large family structures, single room occupancy, shared housing, co-housing, and cooperative-housing.”

Use Smart Growth to Fight Disruptive McMansions, Gentrification and Displacement

As Portland, Oregon, has seen house values rise, its stock of modest affordable housing has been disappearing—replaced by gentrifying McMansions out of scale with their neighbors. The City has proposed a Residential Infill Project to alter the way residential zones work, starting with a low base floor area ratio (FAR) to limit overall bulk of new houses relative to existing ones, then providing bonuses when structures include accessory dwelling units (ADUs) or are designed as ‘plexes.’ By limiting the size of structures that only serve one household, and allowing more flexibility to partition slightly larger buildings for more households, Portland is creating a market for infill housing in a more sustainable land use pattern. The compact form and shared walls of these small-scale multifamily structures dovetails well with Passive House strategies, adding more energy benefits.

Offer Accessory Dwelling Units Everywhere

ADUs are secondary homes either attached or detached from the primary single-family house. There are many terms for them: mother-in-law apartments, garden apartments, backyard cottages, ‘Fonzie Flats’, or laneway houses. Over the last decade, a movement to permit one or even two ADUs per house in cities large and small has spread across the nation.

Policy makers and building professionals can have an important local impact by changing the land use code to let people build these very low impact structures, or by supporting statewide initiatives such as California’s SB 1069. After California passed a law in 2016 with a default model code for ADUs, vaulting over reluctant local zoning boards, permits for ADUs have skyrocketed. In Los Angeles, in the two years prior to the legislation, there were 343 ADU permits. In the two years since, it issued 6,497 ADU permits. In 2018, 20% of all new housing permits in Los Angeles were ADUs, indicative of both the pent-up demand for urban housing options and the potential. Practitioners such as Bryn Davidson at Lanefab (www.lanefab.com) do a great job combining Passive House design and construction with green zoning policy activism.

Make the Most of Infill Opportunities

“What is so promising about U.S. cities and their metropolitan landscapes is that they are replete with large areas (literally hundreds of thousands of acres) ripe for transportation and land use retrofits to organize and foster growth.”

– Harrison Fraker, The Hidden Potential of Sustainable Neighborhoods: Lessons from Low-Carbon Communities

Former industrial sites, dead malls, parking lots, surplus public land, former military installations and corporate campuses, and under-utilized public golf courses are just some of the large parcels that are prime opportunities for infill development. Beyond the sustainability of individual buildings, these development opportunities deserve a systematic approach involving coordination with mass transit and consideration of district energy use, water use and low waste approaches. Envisioning these large-scale brownfield planned redevelopment sites using smart growth principles or LEED for Neighborhood Development standards is a start, and they can also serve as inspiring, innovative case studies for carbon emissions reduction.

Mix More Residential and Commercial Uses

Think of how many car trips for a forgotten dinner ingredient might be eliminated if residential zoning allowed walkable neighborhood corner stores. Or if commercial uses like daycares could exist where families live? Or if residential zones were more permissive of commercial leases for home occupations, professional offices, or live/work models, empowering entrepreneurship, providing walkable services, and creating jobs where no vehicle commute is required? Our communities need housing where jobs are and jobs where housing is. Blending uses can be a powerful green zoning tool to reduce vehicle miles while simultaneously creating more vibrant, complete neighborhoods.


Green zoning isn’t so much a universal prescription, but a reminder to use a long-view, low-carbon lens when deciding future development capacity, especially in low density single-family zones. Land use policy dictates where people live and work, and these policies are either baking in unsustainable dependencies that contribute to climate change or not. Redefining zoning to allow for more households on more parcels and more flexible uses complements the resource and energy efficiency work being done by Passive House professionals. When we use our experience and expertise to advocate for green zoning policies, we’re scaling up our efforts to make our neighborhoods, towns and cities active agents against climate change. We’re simultaneously optimizing materials resource efficiency, making it easier and cheaper to attain low carbon operations and low embodied carbon targets at once.

Matt Hutchins

Matt Hutchins

As one of the founders of CAST architecture, Matt has spent more than twenty years working to increase the vitality of the city and the envi...

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