Targeting net-zero emissions, Seattle turns to deep-green building retrofits

Seattle has long been lauded for its sustainable credentials — the nation’s first green-building goal for public buildings, the first large electric utility in the United States to go carbon neutral, early and ardent adoption of Kyoto Protocol targets. It wasn’t surprising, then, when five years ago it embarked upon one of the nation’s most aggressive sustainability goals to date: net-zero greenhouse gas emissions by 2050. To meet this target, Seattle officials vowed to slash the carbon footprint of everything from bus fleets to waste streams.

Scouring for carbon-reduction opportunities, they soon found a key carbon culprit: buildings. Seattle’s buildings account for a good chunk of its greenhouse gas emissions — 21%, according to the City’s 2013 Climate Action Plan. (Most of these emissions stem from space heating and water heating.)

And Seattle is not alone. As cities around the world race to meet greenhouse gas targets (a key focus of this month’s United Nations Climate Change Conference, or COP22, in Marrakech), recent research suggests that a suite of building-focused strategies known as “deep-green retrofits” can put aggressive carbon reductions within reach.

Taking aim at a “huge wedge” of emissions

Last year, with a grant provided through the federal Climate Action Champions initiative, Seattle tackled one of the thorniest challenges involved in greening buildings: retrofitting the existing building stock.

Working with Lawrence Berkeley National Laboratory, a team from Arup analyzed a typical Seattle building: a six-story, 30-unit residential property. “In terms of square footage, almost 50% of the buildings in the city are very similar to this building,” said Martin Howell, an energy and sustainability expert in Arup’s Los Angeles office. “It’s a huge wedge of their carbon emissions.”

Research suggests that a suite of building-focused strategies known as ‘deep-green retrofits’ can put aggressive carbon reductions within reach.

The team adopted a two-step process to reduce emissions. First, it looked for ways to make the building as energy-efficient as possible — “the best bang for your buck,” according to Howell. After exhausting options for reducing energy consumption, it explored opportunities to meet the remaining power requirements with on-site renewables.

The first step resulted in a list of 18 opportunities to reduce emissions, ranging from relatively low-hanging fruit — replacing T12 fluorescent lighting with LEDs, for example, and adding humidity sensors that shut off dryers when laundry is dry — to deep-green (i.e., more intensive) measures such as façade upgrades that improve thermal performance. The team estimated that implementing a short list of six of these measures could cut the building’s overall energy consumption by 39%.

The second phase of the research also revealed promising results. By adding on-site renewable generation, the building could slash the energy draw from the grid by 53% when compared to the current building.

Roof of the Seattle residential building studied. Rooftop solar panels could provide approximately 15% of the building's energy needs.

Roof of the Seattle residential building studied by Arup. Solar panels could provide approximately 15% of the building’s energy needs.

When modeled across the multifamily building portfolio citywide, the measures would cut Seattle’s overall greenhouse gas emissions by an estimated 25% — a significant step toward its net-zero goal.

Bring on the heat pumps

Of the most promising measures considered, two of the boldest would entail a fundamental shift in the way Seattle heats its homes and offices.

Currently, the study building uses electric resistance heating for apartments. This technology, which functions something like the heating element in an electric kettle, is widely used in both commercial and residential buildings across the United States.

Electric resistance heating unit in Seattle study building.

Electric resistance heating unit in Seattle study building

Switching to high-efficiency electric heat would not only save energy, but also take advantage of the city’s green grid — electricity through Seattle City Light has been nearly carbon-neutral since 2005, thanks largely to the region’s bountiful hydropower. It would also reduce peak electricity consumption, which, extrapolated to a larger scale, means less expensive and smaller infrastructure, as well as fewer power stations. To that end, the team proposed heating apartments with a technology called air-source heat pumps that could cut the electricity required for heating by 55%.

Meanwhile, Arup found that nearly one-third of the building’s energy use was devoted to heating hot water with a natural-gas-heated boiler. Switching to an air-source-heat-pump water heater could slash energy consumption as well as carbon emissions; such systems can be more than three times as efficient as conventional units.

In the wake of this study, Seattle has amended its energy code to strongly favor heat-pump technology over electric resistance and fossil fuel heating.

A farsighted framework for deep-green solutions

Technologies like heat pumps are part of a broader trend in building design called electrification, which replaces equipment powered by fossil fuels with units that plug into the electric grid. As more and more renewable power sources get integrated into power grids over time, the theory runs, buildings can be gradually weaned off carbon.

Due to Seattle’s low energy costs, such building upgrades could have long payback periods. Still, as they are rolled out under ever more stringent standards, the price tag for carbon-saving solutions will drop.

Building political and financial infrastructure

Perhaps even more importantly, cities like Seattle understand that tackling these issues now will allow them to build the political and economic systems needed to produce change over the long run. Large-scale implementation of innovative energy-storage systems or deep-green retrofits will require extensive coordination with a range of stakeholders in the city, from utility companies to building owners and average citizens — something that can’t be achieved overnight.

As technologies evolve to make some of these changes possible on a broad scale, the cities that have planned ahead will be the ones to reap the benefits soonest.

 

Questions or comments for Jeff Byles or Martin Howell? Contact jeff@beingheredesign.com or martin.howell@arup.com.

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