Many US cities are addressing climate change by setting goals to reduce their greenhouse
gas (GHG) emissions by a specified amount within a specified time period. In order to
achieve these goals, reducing emissions from existing buildings is crucial. Many cities
are passing legislation to target existing buildings through benchmarking, auditing,
retuning, or energy or emissions performance standards. As cities design legislation,
they must consider the timing of the policies, how to prioritize building types and sizes,
and how these design decisions will impact the city’s emissions. This paper addresses
these questions for one particular US city: Seattle, Washington. A model of Seattle’s
building stock was created with benchmarking and tax assessor data. It was then used
to predict GHG emissions reductions due to different policy implementations for existing
commercial and multifamily buildings. Key findings are: (1) the proposed emissions policy
is expected to reduce cumulative emissions from buildings by 19% between 2020 and
2050; (2) delaying the implementation of the policy by five years could limit savings to
12%; and (3) including smaller buildings in the policy could increase savings to 34%. The
lessons learned and how this can be used by other cities are discussed.