Passivhaus or Passive House buildings are low-energy buildings in which the design is driven by quality and comfort, hence achieving acceptable levels of comfort through post-heating or post-cooling of fresh air. Additionally, Passivhaus building design follows the Passivhaus design criteria, as described in the Passive House Planning Package (PHPP). This article aims to introduce the Passivhaus background, development, and basic design principles. Finally, it also presents a brief description of the performance of Passivhaus buildings.