Economic carbon neutrality by 2050 is required to avoid catastrophic climate change. New Zero Energy Buildings (ZEB) help, but presuming that all buildings constructed starting in 2030 are ZEBs, the buildings sector achieves carbon neutrality 30-80 years too late. Case studies continue proving the technological feasibility and methods of ZEB funding, construction, contracting, and promotion. The remaining barriers to constructing all ZEB are perception and market based. Carbon neutrality in buildings requires a ZEB-focused effort on evaluating, retrofitting, and benchmarking the completely under-served sector of existing buildings.

This paper documents a journey that began with “Why is the chiller running during winter?” Eight years later, after focused and end-of-life investments, the 280,000 ft 2 Ohio History Center museum facility consumes 50% less energy, achieving a deep energy retrofit. Combining controls optimizations, planned efficiency investments, and potential capital projects could further reduce the EUI towards a ZEB-ready range near 40 kBtu/ft 2 -yr. The facility’s site can physically house enough photovoltaics to generate the remaining energy needs for ZEB.

This story involves an engaged and empowered owner with limited funding and motivated staff that approached efficiency through tactical investment, integrated design, and deliberate commissioning. This paper describes a justifiable path for existing buildings to get ZEB-ready at no additional lifetime cost and to ZEB status with economically viable renewable energy options. The paper aspires to direct the ZEB community’s focus towards existing buildings and unlocking their potential.