Case Study: Kāinga Ora Passive House standard

Summary

New Zealand's building and construction sector contributes to around 15-20% of New Zealand's overall carbon emissions. It's critical for the construction industry to play a significant part in reducing carbon emissions for the future of Aotearoa New Zealand.

Kāinga Ora - Homes and Communities is tackling this challenge through its Carbon Neutral Housing Programme, including committing to reducing carbon in its residential developments by 2030. One of Kāinga Ora's key carbon reduction projects is its new development, Bader Ventura, located in Māngere, Auckland. It's the state housing provider's first residential development using the Passive House standard.

The Bader Ventura development includes 18 homes in three-storey walk up buildings, which will be 85% cheaper for tenants to cool and heat and will become Australasia's first central government public housing development that meets the Passive House standard.

During construction, Kāinga Ora committed to sharing lessons learnt to support the wider sector in adopting the Passive House standard. This case study is focussed on the design phase, which is now finished, and construction will finish in mid-2023.

Kāinga Ora case study video

Approach

In 2020, Kāinga Ora established its Carbon Neutral Housing Programme, which aims to decarbonise public housing construction activity to low carbon by 2030. The programme focuses on three primary areas: reducing operational energy use for customers to have affordable heating and cooling; reducing carbon in building materials and waste; and leading and supporting industry change.

The Carbon Neutral Housing Programme is focussed on how Kāinga Ora can start achieving future government emissions targets using today's technology and how they can bring the industry on this journey. The programme roadmap created a strong foundation for the Kāinga Ora project team to explore different innovations and practices to achieve the Passive House standard during the design phase of Bader Ventura.

The focus of Bader Ventura is to improve overall energy efficiency and to reduce thermal bridging, which can be achieved by designing to the Passive House standard. Thermal bridges are formed when a certain material has a higher heat transfer than surrounding materials. For example, if you have a concrete structure passing through insulation, it will act as a thermal bridge. The problem with thermal bridges is that they are a pathway for heat loss, resulting in a cold home and/or higher heating costs. The cooler internal surface temperature caused by the bridge can also cause condensation on internal surfaces, which contributes to mould growth.

Bader Ventura is a Kāinga Ora pilot project demonstrating the Passive House standard to test whether this certification can help drive energy efficient outcomes in a cost-effective way, and show how it can be replicated across the sector. The decision to build to the Passive House standard was triggered by a conversation between Kāinga Ora's Development Manager and suppliers about thermally broken windows. After realising that these windows were available for around the same cost as standard windows, they discovered that the Passive House standard was a feasible option if the entire project team committed to the idea.

One of the main hurdles was getting the design team on board, as a lot of the design had already been completed and would need to be reworked. There was also resistance in moving away from traditional design and construction processes.

A Passive House consultant joined the team to help with the transition, and Kāinga Ora and the design team worked collaboratively to understand the issues and work through solutions. Unlike other certification standards, Passive House is pass or fail, so there were no partial credits or optional criteria. Early discussions around aiming for the Passive House standard required a high level of trust, expertise and partnership across the project team.

The time and costs involved in gaining the Passive House design endorsement were higher than other projects, partly due to adopting the standard once the design process was already underway. Kāinga Ora expect the benefits to be delivered across the lifetime of the finished building, which is more important than short-term gains from saving money during the construction phase.

The integrated design process to achieve the standard helped the team work together toward a common goal – with building services engineers, architects, Passive House specialists and the construction team all collaborating throughout the process.

Outcomes and benefits

Reducing carbon and improving residents' wellbeing

Bader Ventura will deliver a reduced operational carbon footprint of more than 70% and reduce heating costs for residents by around 85% (compared to a similar sized dwelling built to a 6 Homestar rating). These significant benefits mean residents will have heating and cooling costs of about $1 per day and will enjoy comfortable year-round temperatures and fresh filtered air.

Enabling industry transformation

Kāinga Ora has committed to continuously reporting its performance and key learnings to the industry throughout the project. The only way to transition to a low emissions future is by working together as a sector and collaborating through multiple channels, such as webinars, site visits, events, reports and more.

MBIE's Building for Climate Change programme was established in 2020 to guide the building and construction sector to achieve its contribution to New Zealand's emissions reduction targets, and make sure our buildings are prepared for changing climate conditions.

The Kāinga Ora Building Roadmap is aligned to policies like these, sets out measures for lower carbon construction and outlines the dates when Kāinga Ora and the wider sector are expected to meet certain targets. Kāinga Ora is aligning its decarbonisation efforts with central government policy to provide evidence to the sector that lower carbon buildings are possible with today's technology.

More information about the Building for Climate Change programme(external link) - mbie.govt.nz

More information about the Kāinga Ora Building Roadmap(external link) - kaingaora.govt.nz

Piloting new approaches to improve productivity

Designing and building to the Passive House standard was more expensive than traditional approaches – mainly because the project team and Kāinga Ora didn't have any experience with the requirements, they had to learn along the way and Passive House standards were added partway through the design process. The learnings and templates from Bader Ventura will be used on future developments to improve productivity and energy efficiency, such as on the Bader Harvard development in Mangere, Auckland.

Lessons learnt

The lessons learnt from the design phase are outlined below. More insights from the construction and post-occupancy phases will be shared by Kāinga Ora once completed.

Identify the environmental standards before starting design

The Passive House standard was added into the design requirements after much of the design work was already complete. It was important for Kāinga Ora to be open to innovation and suggestions from the project team, and ultimately, they found that the standard was the right approach for Bader Ventura. However, it's important to understand the rework, cost and time delays from changing direction during the design phase.

Build a strong team with a passion for environmental outcomes

Designing and building to the Passive House standard requires a different level of commitment, skill and training for the team working on the development, which can seem daunting at the start of a project. There was some resistance from consultants around the level of detail required and considering how to work with the variety of standards and systems.

To overcome this challenge the development team needed to be determined and carefully plan an integrated design process that brought everyone on the collective journey. This involved a series of workshops, meetings and iterations to develop the design. The designers, engineers and builders all worked together to drive specific outcomes to achieve the Passive House standard, such as overcoming thermal bridging issues and ensuring a thermal envelope compliant with the standard.

Project partners

Kāinga Ora also acknowledges the wealth of expertise and assistance provided by its main partners on the project including:

• Precision Construction – building partner
• Peddlethorp – architects
• Oculus Architectural Engineering – passive house lead and façade engineers
• Kirk Roberts – structural engineers
• 2PiR Consulting – building services engineers
• Sustainable Engineering – passive house certifiers View a series of informative NZ Passive House case studies(external link).

Many of these companies also have links to helpful resources about Passive House construction on their websites.

Read more information about the Bader Ventura project(external link) - kaingaora.govt.nz

Read our guide on how to implement a similar approach in your business.