This document provides an overview of Passivhaus and discusses its application in California. It summarizes that Passivhaus is a super-insulated and airtight building standard that is significantly more efficient than Title 24 requirements, with wall and roof insulation R-values that are 2-3 times higher. Several completed Passivhaus projects in California are mentioned, including both new construction and retrofits, and some lessons learned are provided around foundation insulation, overheating issues, and the importance of details and flashing. Monitoring studies have found Passivhaus projects in California perform as predicted in terms of energy efficiency.