Passive house

Passive house (Passivhaus) is a voluntary building performance standard for very high energy efficiency and thermal comfort that substantially reduces a building’s carbon footprint. Buildings certified to the standard are ultra-low energy and typically require very little energy for space heating or cooling. The approach is used for housing and for non-residential buildings such as offices, schools, kindergartens and healthcare facilities. Energy efficiency is integral to architectural design rather than an add-on. Although most common in new construction, the principles are also applied in deep renovations. As of January 2025, projects certified by the Passive House Institute (PHI) comprise over 47,400 units with about 4.32 million m² of treated floor area (TFA) worldwide; the public PHI database lists nearly 6,000 projects. In North America, the Passive House Institute US (PHIUS) reported 500+ total certified projects and ~1.6 million ft² certified in 2024 alone, with 4.4 million ft² design-certified that year. While early adoption concentrated in German-speaking countries and Scandinavia, certified projects are now documented across diverse climate zones, including hot-humid and tropical regions.

History

The term passive house was originally used in the 1970s for buildings emphasizing passive solar strategies. Since the 1990s, it instead denotes meeting specific quantified PHI certification criteria (space conditioning, primary energy, airtightness and comfort requirements). The standard originated from a 1988 discussion between Bo Adamson (Lund University) and Wolfgang Feist (then at the Institute for Housing and Environment, Darmstadt), followed by research supported by the state of Hesse. Passive solar strategies are not required, though often form part of the approach to meet the certification criteria. North American “superinsulation” pioneers of the 1970s (e.g., the Saskatchewan Conservation House and the Leger House) provided important technical precursors, including heat-recovery ventilation and airtightness testing.

First examples Four terraced houses in Darmstadt-Kranichstein (1990–1991) are widely cited as the first built to what became the Passive House standard.

Further implementation

The Passivhaus-Institut (PHI) was founded in 1996 in Darmstadt to develop, promote and certify to the standard. By 2010 an estimated 25,000+ Passive House buildings existed worldwide. The concept has since been demonstrated at scale. Gaobeidian, China, hosts what is reported as the world’s largest Passive House development (Railway City), with several hundred thousand m² of certified area built in phases since 2019. The world’s tallest certified Passive House building is the 88 m Bolueta tower in Bilbao, Spain (2018). In the United States, Katrin Klingenberg’s 2003 “Smith House” (Urbana, IL) catalyzed a movement that led to the creation of PHIUS (2007). PHIUS has since certified hundreds of projects; New York City’s Park Avenue Green (2019) was recognized as North America’s largest Passive House affordable housing project at the time. In the UK health sector, the Passivhaus-certified Foleshill Health Centre (Coventry, opened 2021) demonstrated substantial energy savings in operation and a replicable delivery model for NHS facilities.

Standards

While techniques such as superinsulation predate the standard, Passive House (PHI) specifies quantitative performance criteria and quality assurance. Key requirements include:

Annual space heating (and, in suitable climates, cooling) demand ≤ 15 kWh/m2/a (0.0047 MJ/sq ft/sq ft) or peak heat load ≤ 10 W/m2 (0.0012 hp/sq ft), as calculated with the Passive House Planning Package (PHPP), using local climate data. Airtightness: n50 ≤ 0.6 h⁻¹ at ±50 Pa, measured via a blower-door test. Efficient mechanical ventilation with heat recovery (typically ≥75% sensible efficiency). Whole-building primary energy/renewable energy limits as defined by PHI (see PHI documentation).

Standards in North America: PHI and PHIUS+ Two related but distinct standards operate in North America:

PHI (Darmstadt): the original international Passive House standard and certification system using PHPP and PHI quality assurance. PHIUS+ (Chicago): climate-specific performance targets (CORE/ZERO/REVIVE families) with on-site QA/QC by accredited raters and verifiers; criteria are optimized for carbon and cost within each North American climate zone. The two programs use different energy models and protocols and certify independently.

Construction costs Passive House building costs vary by market, building type, and the experience of the builder and their team. Reported cost premiums for Passive House construction over conventional construction have ranged from ~5–10% in Germany, the UK and the US, with reductions noted as supply chains mature. The specific drivers of building cost and complexity vary, but relative to basic Code-compliant construction, Passive Houses typically include superinsulation of the envelope, requiring greater thickness and complexity of the wall assembly in particular, and particular attention to air, water, and vapour barriers, including at all penetrations. They also include very high performance window and exterior door systems. Cost premiums are partially offset by downsized or eliminated conventional heating/cooling systems, and lower operating costs over the building life cycle. Delivery at cost parity with standard code buildings has been demonstrated in some German multifamily projects (e.g., Vauban, Freiburg). High-latitude locations (>60°N) can face higher envelope and glazing costs to meet targets. It is possible to retrofit passive house features to an existing building, but this is expensive. In the UK an architect incurred a total cost to adapt a small four-bedroom 1960s house of about £80,000, over ten years to spread the cost, without including additional costs for architectural work. The windows cost about £30,000; making the house airtight about £5,000. On a hot day, the temperature inside was about 10°C cooler than outside. In winter a single radiator was enough to heat the whole house, with a reduction of 88% in required energy. However, in a heatwave with hot nights, unusual in the UK, the temperature during the day rose to about the night-time ambient temperature. While retrofitting to full passive house standard is expensive, it has been suggested that "even doing the 50% best is massive in terms of energy bills".

Design and construction

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