Passive House Is a Performance Standard, Not a Design Style
Passive House (Passivhaus in its German origin) is a rigorous energy performance standard for buildings that targets a heating energy demand so low that conventional heating systems can be dramatically downsized or eliminated. Buildings certified to the Passive House standard (through either PHI, the European institute, or PHIUS, the North American certification body) typically use 60–80% less energy for space conditioning than code-minimum buildings. The ARE PPD tests Passive House concepts as part of its sustainability and building systems content because the five Passive House principles describe the physics of building energy performance in precise, teachable terms.
The Five Passive House Principles
1. Super-insulation: Passive House requires insulation levels far above code minimum - typically R-40 to R-60+ for walls and R-60 to R-100 for roofs in North American climates. This dramatically reduces conductive heat loss through the opaque envelope. Wall assemblies must be carefully designed to achieve these R-values while controlling moisture and maintaining structural integrity.
2. Thermal bridge-free construction: A thermal bridge is a localized area of low thermal resistance in an otherwise well-insulated assembly - for example, a steel stud spanning between the warm interior and the cold exterior, or a concrete slab extending through an exterior wall. Even small thermal bridges can dramatically reduce the effective R-value of an assembly. Passive House construction requires continuous insulation outside the structure (to isolate thermal bridges), insulated slab edges, and careful detailing at window openings, balconies, and penetrations.
3. Airtight construction: Air leakage is a major source of heat loss in conventional buildings. Passive House requires an airtight building envelope verified by blower door test to an air leakage rate of 0.6 ACH50 or less. This requires a continuous air barrier, careful detailing at penetrations, and quality control during construction to ensure continuity.
4. Heat recovery ventilation (HRV/ERV): An airtight building needs mechanical ventilation for air quality. A heat recovery ventilator (HRV) exhausts stale air while capturing 80–95% of its thermal energy to pre-heat or pre-cool incoming fresh air. In humid climates, an energy recovery ventilator (ERV) transfers both heat and moisture, improving dehumidification efficiency.
5. High-performance windows: South-facing windows are sized to admit passive solar gain in winter; all windows must have U-factors and SHGC values consistent with the climate strategy. Triple-pane windows are typical in colder climates (U-factor 0.15 or lower).
Passive House vs. ASHRAE 90.1
ASHRAE 90.1 is a code-based minimum standard for energy efficiency in commercial buildings. It sets prescriptive requirements for envelope, lighting power density, and HVAC efficiency but does not mandate the integrated systems approach of Passive House. Passive House projects typically exceed ASHRAE 90.1 requirements by a wide margin. The difference is that Passive House is a performance-based outcome standard (measured energy use) rather than a prescriptive compliance path.
Key ARE PPD Exam Points
- Passive House requires super-insulation, thermal bridge elimination, airtight construction (0.6 ACH50), HRV, and high-performance windows.
- Thermal bridges bypass insulation; continuous exterior insulation eliminates structural thermal bridges.
- HRV captures 80–95% of exhaust air heat; ERV adds moisture exchange for humid climates.
- Blower door testing at 50 Pa pressure differential verifies airtightness performance.
- Passive House certification is available through PHI (European) or PHIUS (North American) with slightly different criteria.
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