Center for the Built Environment

California has set goals for zero net energy buildings and greenhouse gas emissions reductions that will be achieved in part through the state’s building energy codes. Decisions about what measures to include in code are informed by building energy models that rely on historical climate data. However, even under moderate emissions scenarios, by 2050 mean temperatures in California are projected to increase by almost 4 degrees Fahrenheit compared to pre-1990 levels and there is evidence that current day temperatures are already shifted from the historical record. Not only do these energy models underlie cost-effectiveness analyses which influence the prescriptive code, they inform building system selection and sizing, and they are the basis for program incentive awards. While the general trends are predictable – as temperatures increase, average cooling energy increases and heating decreases – the effects of future climate on the state’s building policies have not been thoroughly analyzed. To what extent will lower winter heating loads increase the business case for buildings to electrify? Under future climate, are increased cooling efficiency measures cost-effective that aren’t today? How will future climate affect the energy and emissions performance of California’s buildings and what policies can be adopted today to future-proof them? This paper starts to address these questions by examining the performance of prototype buildings within a subset of California’s climate zones under past and future climate scenarios. It models energy efficiency measure variants to these prototypes and compares the energy, emission, cost, and thermal load outcomes under future climate scenarios compared to historical design weather and makes policy recommendations based on the results.