Passive House — Passivhaus in the original German — is a voluntary, performance-based standard for buildings that need almost no active heating or cooling. It was formalised by Dr Wolfgang Feist and the Passivhaus Institut (PHI) in Darmstadt in the early 1990s, building on earlier superinsulation and low-energy research from North America and Scandinavia. The first certified dwellings, built in Darmstadt-Kranichstein in 1991, are still performing to specification more than three decades later.
Crucially, Passive House is not a product, a construction system or a brand. It is a set of physics-based performance targets, verified by calculation (PHPP) and on-site measurement (the blower door test). A building either meets the numbers or it does not. That measurability is exactly why it matters to a building-performance consultancy: it replaces opinion with evidence.
The Passive House performance targets
Classic Passive House certification for new build requires a building to meet hard, measured limits. These are the figures every Passive House Designer works to:
| Metric | Limit | What it controls |
|---|---|---|
| Space heating demand | ≤ 15 kWh/m²·yr | Annual energy needed to keep the building warm |
| Heating load (alt.) | ≤ 10 W/m² | Peak heating power — small enough to heat via the ventilation air |
| Airtightness | ≤ 0.6 ACH₅₀ | Uncontrolled air leakage through the envelope |
| Primary energy (PER) | ≤ 60 kWh/m²·yr | Total renewable primary energy for all uses |
| Overheating | ≤ 10% of hours > 25 °C | Summer comfort / overheating frequency |
Fabric first: the five principles
Passive House achieves these targets through five interdependent fabric-first principles. None works in isolation — they form a single, coherent thermal and moisture strategy:
- Continuous, high levels of insulation (a 'thermal envelope' with no weak spots).
- Thermal-bridge-free detailing (ψ ≤ 0.01 W/m·K at junctions).
- An airtight envelope (≤ 0.6 ACH₅₀), with a continuous, identifiable air barrier.
- High-performance glazing and doors (triple glazing, insulated frames, warm-edge spacers).
- Mechanical Ventilation with Heat Recovery (MVHR) delivering continuous filtered fresh air while recovering 75–95% of the heat.
Read the dedicated articles below for the building physics behind each principle. They are written to be useful to homeowners and architects alike — if you are a designer or engineer, you should still take something away.
How Passive House relates to retrofit (EnerPHit)
Most of the UK's homes are already built, so the bigger opportunity is retrofit. PHI's EnerPHit standard applies Passive House principles to existing buildings, where geometry, party walls and conservation constraints make the new-build targets impractical. EnerPHit relaxes the heating-demand limit (typically ≤ 25 kWh/m²·yr in a cool-temperate climate, or a component-by-component route based on certified U-values) while keeping the same uncompromising attention to airtightness, thermal bridging, ventilation and — most importantly — moisture safety.
Start here
Work through the cluster below in order, or jump to the topic you need. Each article links to the related services and to the next logical read.