What is the difference between the AECB and Passivhaus certification standards? Read Greengauge’s handy guide below.

The energy standards of the AECB and the Passivhaus Institute have varying levels of requirements but follow similar principles, including energy modelling through PHPP, evidence requirements, and following a certification procedure.

Benefits

Energy efficiency
Low heating demand and reduced performance gap. This leads to lower energy bills and less impact on the environment.

Superior comfort
Consistent and comfortable temperature throughout the year, with minimal temperature variations and drafts.

Health and wellbeing
Mechanical ventilation maintains indoor air quality for occupant health.

Durability
Buildings are constructed with high-quality materials and designed to be airtight and moisture-resistant, leading to reduced maintenance costs over time.

Improved Quality Assurance
The use of PHPP (Passivhaus Planning Package) improves the accuracy of the energy modelling, and the certification process (evidence collection and certifier reviews) reduces the performance gap.

Key Performance Criteria

Design Principles 

Continuous insulation 

High levels of insulation with thermal bridges minimised and accounted for in energy modelling.

Form and solar gain

Efficient form factor (low surface area to floor area ratio), with glazing balanced to provide good levels of daylight and winter solar gain, while avoiding overheating. 

Airtightness

Airtightness reduces heat loss, improves comfort and protects the building fabric. 

High performing windows 

Passivhaus in the UK requires triple glazed windows for high comfort levels. 

Building services

Passivhaus is flexible on heating strategy, but efficient systems are required to meet the PER target. AECB New Build and Retrofit Step-By-Step require the use of a heat pump, apart from exceptional circumstances where electric heating may be permitted. Continuous mechanical ventilation is required, with Passivhaus requiring MVHR (Mechanical Ventilation with Heat Recovery).

PHPP (Passivhaus Planning Package) 

A highly detailed energy modelling tool used for informing building design and demonstrating compliance with AECB and Passivhaus. Includes heating demand, heating load, PER and overheating. This will be used by the PHPP modeller throughout the design process, incorporating any design changes to check compliance with the standards.

Construction 

Education and training 

Construction team members should be familiar with the requirements of AECB/Passivhaus and would benefit from relevant training such as the Passivhaus Contractor course or training on airtightness. 

Team collaboration

Maintain open communication channels between the architect, energy consultant, construction teams, subcontractors, and suppliers. 

Airtightness 

Employ an air tightness champion and perform interim airtightness tests while the air barrier can still be accessed and remedied. 

Quality Control 

Focus on high quality workmanship, with an airtight construction with no gaps between insulation.

Evidence

Various evidence is required from the construction phase, including photographs, air test certificates and commissioning certificates. Photographs of specific aspects are required demonstrate the installation is of high quality and matches the design. 

Certification Procedure 

AECB certification requires an AECB PHPP modeller and AECB certifier (this can be the same person). Passivhaus certification requires a 3rd party certifier, separate to the Passivhaus Designer/Consultant.

In both cases, PHPP modelling should be carried out at an early stage (before planning) and reviewed by a certifier to check the project can meet the desired standard or explore which targets can be met. A certifier should then review the project again before construction begins, to check the detailed design meets requirements.

The certifier will then review the construction evidence (photographs and certificates etc.) upon completion. They may also make site visits during the construction process. Finally, the as-built PHPP file and supporting evidence are submitted to the AECB/PHI for lodgement. 

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