"Passive house" is used loosely in architectural coverage to describe well-insulated, airtight homes with a vaguely Scandinavian aesthetic. The Passive House Institute's certification standard is more precise: it evaluates modelled specific heating demand, specific cooling and dehumidification demand, primary energy demand (or renewable primary energy in the newer Passive House Plus and Premium classes), airtightness, and overheating frequency. Visual style is not part of the criteria. The performance thresholds are set for the building as a whole and are climate-dependent. The same design may meet criteria in a cold, dry climate but fail in a hot, humid one. The Passive House Planning Package (PHPP) is the energy-calculation tool used to demonstrate compliance. A certified building must achieve airtightness measured by pressurisation test—typically n₅₀ ≤ 0.6 per hour—and incorporate mechanical ventilation with heat recovery to maintain indoor air quality without relying on infiltration. Window specification, thermal-bridge elimination, and envelope continuity are the main design levers. The Passive House Institute framework (based in Darmstadt, Germany) is distinct from the Phius certification system widely used in North America. Both pursue similar outcomes but use different climate datasets, ventilation standards, and verification procedures. Comparing performance across the two systems requires care. "Passive-inspired" or "passive-house principles" is not equivalent to certified performance. The certification database, maintained by the Passive House Institute, allows verified projects to be searched by climate, building type, and certification class. Editorial caution: Quote thresholds only from the relevant certification criteria for the project type, climate, and class being discussed. Do not conflate the PHI standard with Phius without distinguishing them.