Compact development is one of the biggest opportunities for cities to reduce climate pollution while making life more livable and affordable. That’s why Fill It First strategies are a central part of any strategy to drive Carbon Down and build Community Up.
Cover image: Opportunities for Fill it First housing development. (Source: ReHousing)
We do not use urban land efficiently. There is significant opportunity to house more people on existing residential lots – through a spectrum of solutions ranging from home share to secondary suites to coach houses.
An analysis that OCAF recently commissioned (full report coming soon) from Vancouver-based Boston Consulting focuses on three compact development options that can reduce emissions by 35% to 50% compared to the more commonplace model of single-family detached development. The biggest savings are in day-to-day mobility, followed by operational emissions in housing and embodied carbon in driving and transit.
The analysis looks at four different scenarios for Ottawa to add 15,000 new housing units, compared to a recent average of about 5,500 per year, and assesses the emissions impact of each approach. As the graph above shows, Fill it First strategies deliver significant carbon reduction potential.
- Single detached development, primarily on the urban edge, in areas like Kanata-Stittsville, Barrhaven, Riverside South and Orleans (reference case);
- Hub apartments, defined as new rental apartments in central and suburban hubs for employment or post-secondary education (35% GHG savings);
- Distributed suites, a scenario in which secondary suite renovations are distributed equally across Ottawa neighbourhoods (41% GHG savings);
- Focused suites, consisting of secondary suite renovations in single-family detached homes in central and suburban hubs for employment or post-secondary education (50% GHG savings).
Emissions in the Built Environment
Shifting our urban planning and housing supply enhancement strategies from traditional, single-family detached units to “missing middle development” and “gentle density” is key to getting municipal emissions under control. But to tap into that potential, cities like Ottawa have to unpack the different categories of emissions and understand the characteristics of compact development that deliver the climate benefits we need.
The Boston Consulting research builds upon two basic cornerstones:
- Transportation and buildings account for the lion’s share of greenhouse gas emissions in urban settings. In Ottawa, these categories account for roughly 90% of GHG emissions.
- Each of those buckets divides down into two sub-categories: the operational emissions from driving and heating/cooling buildings, and the embodied emissions in building a home or manufacturing a car or transit vehicle.
These definitions are fairly widely understood, but they lead to a series of insights that go right to the heart of urban emissions and how to control them.
Transportation Makes All the Difference
The analysis draws a clear connection between compact development and the transportation choices that are so decisive in shaping household costs, living patterns and emissions.
The most important planning determinant of household car ownership rates and driving distance––and thus transportation cost, congestion and carbon––is location, specifically proximity to an urban region’s central business district, followed by secondary job hubs and services, notably grocery stores.
Daily commute and long travel distances from suburban or exurban, single-family homes can double or triple a household’s carbon footprint and transportation costs. These patterns of how location and density impact driving hold true across Canadian cities including Ottawa (above) and greater Montréal.
That makes the Boston Consulting analysis an invitation for policymakers to address how land use development patterns impact transportation emissions and costs:
- Having more households located closer together can make transit more efficient and cost-effective, reducing household transportation costs and time on the road.
- More compact development can reduce car ownership and embodied emissions in transportation.
- Prioritizing development of 15-minute neighbourhoods offers people the opportunity to live closer to the amenities they need every day and travel more conveniently to and from work.
For further insight see our blog: Economic, Social & Environmental Benefits of Smart Growth.
Lots of Space in Existing Buildings and on Existing Lots
Our report points to the opportunity to make better use of existing living space and land, while giving homeowners some help on their mortgage payments, with a Fill It First strategy that matches demand with supply.
For a variety of reasons, notably a rapidly aging population and the trend toward smaller families, the fastest growing households for the past several decades have been comprised of one or two people. While once occupied predominantly by families of four, today half of Ottawa’s single detached homes and two-thirds of all Ottawa homes are occupied by just one or two people. Across Ontario, there are an estimated four million empty bedrooms.
The analysis presents policymakers with the opportunity to consider how best to increase residential density, particularly in existing neighourhoods and near public transit, based on these findings:
- In most situations, the greater the square footage of a single-family home, particularly a larger home in a new suburb, the greater its carbon footprint
- Shared walls in multi-unit buildings, large or small, have the potential to reduce energy consumption and carbon emissions from each individual unit
- Small multi-family development, along with more compact home designs, can reduce construction emissions and embodied carbon, on a per home basis.
- Note that the embodied emissions in the Boston Consulting analysis are deliberately conservative, incorporating construction materials, processing, manufacturing and transport – but not maintenance and end-of-life disposal.
- There is significant potential to reduce carbon pollution on a community-wide basis by housing more people on existing residential lots by filling empty bedrooms, building secondary suites or additional dwelling units, especially withing existing neighbourhoods well served by public transit and other amenities.
Future blog posts in this series will look at what it will take to launch a Fill It First strategy for Ottawa, and delve into the financial, physical and regulatory intricacies that need to be addressed to scale this compelling solution to the joint housing and climate crises.