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What is Passivhaus?

Passivhaus is an internationally recognised building performance standard developed by the Passive House Institute (PHI) in Germany.

At it’s core, Passivhaus is primarily about comfort.  It achieves a year-round level of comfort through:   

  • Excellent insulation – continuous thermal envelope.
  • Airtight construction – minimal air leakage.
  • Thermal bridge-free design – prevent heat loss at junctions.
  • High-performance windows – typically triple-glazed with insulated frames.
  • Mechanical ventilation with heat recovery (MVHR) – fresh air without energy loss.

There are several levels of Passivhaus certification, which include:

Classic Passivhaus (New Build)

For new buildings that meet the full standard. All five principles must be applied rigorously.

Space heating demand ≤ 15 kWh/m²/year (a normal building regs compliant new build house in the uk would be ≤ 50 kWh/m²/year)

Primary energy (renewable) ≤ 60 kWh/m²/year

Airtightness ≤ 0.6 ACH @ 50 Pa

Overheating risk < 10% of hours above 25°C

 

 

EnerPHit (Retrofit)

A slightly relaxed standard for existing buildings, where full Passivhaus performance may not be achievable due to constraints (orientation, structure, etc.).

Space heating demand ≤ 25 kWh/m²/year (an unmodernised Victorian house in the uk  would be roughly 95-110 kWh/m²/year)

Airtightness ≤ 1.0 ACH @ 50 Pa

 

 

 

 

Passivhaus Plus / Premium

Combines Passivhaus with on-site renewable energy:

Plus – Net-zero with some on-site generation

Premium – Net-positive energy with high renewables output

 

 

 

Step-by-Step (Phased) EnerPHit / Retrofit Option

This is a phased approach developed by PHI for retrofits when full work cannot be completed at once.

Why use Step-by-Step?

  • Budget or time constraints.
  • Complex buildings.
  • Need to keep parts of the building in use.

How it works:

  1. Planning phase:
    • Create a masterplan using PHPP (Passive House Planning Package).
    • Define all retrofit measures and their sequence.
    • Identify interdependencies (e.g., don’t insulate internally now if you plan to replace windows later).
  2. Execution phase:
    • Retrofit in stages (e.g., roof > windows > walls > systems).
    • Each step must avoid lock-in effects (changes that would prevent future improvements).
    • Document every stage and update PHPP.
  3. Final stage:
    • Once all measures are complete, the building can be certified to EnerPHit Step-by-Step.

Benefits:

  • Practical for occupied homes.
  • Reduces financial burden of upfront full retrofit.
  • Preserves long-term performance goals.

Tools & Certification

  • PHPP (Passive House Planning Package) – used to model and verify performance.
  • DesignPH – 3D SketchUp plugin to assist with geometry inputs for PHPP.
  • Certification through accredited PHI certifiers.

Summary: Why choose Passivhaus?

Up to 90% less heating energy
Extremely comfortable and quiet homes
Built to last and perform as designed
Can be applied fully or incrementally
Aligns with net-zero carbon goals