The first residents moved into Hammarby Sjostad in Stockholm in 2002, which was developed as a sustainable neighbourhood with a closed loop urban metabolism approach

For my PhD research project, I'm visiting three cities with some of the most aggressive greenhouse gas emission reduction targets in the world. On my trips to London and Stockholm last fall, I asked policy makers, research organizations and industry about their efforts to transform urban built environments in order to achieve deep greenhouse gas emission cuts. I have just arrived in San Francisco to ask individuals here the same questions. But in all three places, I am also getting a chance to see decarbonization efforts in action in some of the most progressive sustainable buildings and communities.

In London last September, buildings across the city opened their doors to guests for Open House London. Some people waited in the huge line to try to get to the top of the Gherkin, but I followed the green building track. It led me back and forth across the city from homes to office blocks to district heating tunnels under the Thames.

London social housing unit built in 1870 that has achieved a 77% greenhouse gas emission reduction

This Victorian terrace is a pretty classic London building, but this one is a little different than its neighbours - it achieved a 77% reduction in greenhouse gas emissions. Originally built in 1870, it now boasts new insulation, thicker (but still heritage approved) windows, heat recovery units and a solar hot water system on the roof. I was guided through by the resident on a sunny afternoon with about 15 or 20 others, most of whom seemed interested in tackling their own terrace renovation for energy and greenhouse gas emission reduction. The renovation on this social housing unit was fully funded as a pilot project for the Superhomes scheme promoted by the local Camden Council.

London office building that achieved sustainability performance in the top 1% of UK non-domestic new buildings

The Camden Council Building at 5 Pancras Square achieved a BREEAM rating of Outstanding, which is meant to signify sustainability performance in the top 1% of UK new non-domestic buildings. The design  for this building incorporates a number of passive design elements, like high levels of air-tightness and insulation in the external envelope, high levels of thermal mass, and windows that open to ventilate and purge heat. Our tour guide, a Camden Council employee that works in the building, didn't notice many of these features day-to-day since the building mostly feels like a regular office tower.

On my trip to Stockholm, I learned about efforts their to target the sustainability performance of whole new neighbourhoods within the city. In 1996, the city began redevelopment of Hammarby Sjostad on an urban brownfield site. The neighbourhood aimed to be twice as efficient as a typical one. The closed loop urban metabolism model that was developed through this experience is well-known in urban planning circles since Stockholm policy makers exported their experiences around the world to other sustainable communities. But this knowledge is also being applied a little closer to home in the Stockholm Royal Seaport development.

The Stockholm Royal Seaport neighbourhood has high standards for sustainability performance to push forward innovation

Stockholm urban planners and developers are now tackling a new sustainable neighbourhood redevelopment scheme called the Stockholm Royal Seaport or Norra Djurgårdsstaden. The land is owned by the City of Stockholm and they have set high standards for the new development. For new buildings, they are trying to achieve the very efficient standard of 55 kWh per square meter per year performance (the national standard was 90 kWh/m per year when they first started the redevelopment). The development also aims to meet city targets of greenhouse gas emissions below 1.5 ton per person by 2020 and fossil fuel free by 2030. Multiple developers and companies are working with the each other and with the city in collaborative processes to try to innovate to achieve these goals. Developers are motivated to participate not only because this is highly valuable urban land, but also because involvement in the innovation process creates cutting edge sustainable building capabilities within their operations that they can then offer to other clients.

The Järva project tackled the retrofit of these existing residential towers to achieve significantly improved energy efficiency performance

The retrofit of existing buildings is also being tackled in Stockholm. About half an hour by transit from central station is a neighbourhood made up of older low to medium rise buildings. The buildings in this picture don't stand out much from their neighbours, but they've been overhauled to improve their energy performance. Solar photovoltaics were installed and insulation, the envelope, windows, doors, and the heating system were all replaced to improve energy efficiency.  The performance of the building was 137 kWh/m per year before retrofit and after retrofit it was measured at 89 kWh/m per year. Since many estimates suggest that 80% of existing urban buildings will still be in place in 2050, retrofits like these are clearly a key aspect of urban decarbonization.

The San Francisco City Hall has achieved LEED Platinum certification in the Existing Building Operations and Maintenance category

Finally, I've just arrived in San Francisco but I've already taken a tour of the 101 year old City Hall. It just recently became the oldest building in the US to achieve LEED Platinum certification in the Existing Building Operations and Maintenance category. Like all municipal buildings in San Francisco, it is supplied by 100% carbon free power. To achieve certification, the heating and ventilation system was reconfigured and significant water-efficiency upgrades were installed. It is 90% more efficient than similar buildings in the US. Unfortunately, the tour doesn't yet include these details or bring visitors' attention to the LEED status, but hopefully it will be updated soon. I've just started my research in San Francisco and look forward to speaking with people working on urban decarbonization here. 

I've certainly seen some cutting edge sustainable urban buildings so far in my research travels. Looking across all three places, I hope to get a better sense of decarbonization as it rolls out on the ground and what the politics of transformative decarbonization look like in practice.