Towards a high-performance future

This Issue This is a part of the High-performance buildings feature

By - , Build 185

As we move further into the 21st century, we face two interconnected challenges for our sector – improving building performance to create healthier indoor conditions while also finding ways to reduce greenhouse gas emissions.

HIGH-PERFORMANCE buildings are key to providing solutions for the complex challenges we currently face.

Facing the challenges

We should be aiming for a future where all New Zealand buildings are comfortable and healthy for people to live, learn and work in. People deserve spaces they can afford to maintain at a comfortable temperature with minimal power use where there is adequate ventilation to control indoor moisture and other pollutants in a way that works for the building occupants and their living habits. We need to reach a point where the prevalence of cold and mould currently seen in many of our buildings is history.

At the same time, we’re facing the challenge of reducing greenhouse gas emissions. New Zealand climate legislation sets a net-zero target for emissions by 2050. Buildings contribute up to an estimated 20% of New Zealand’s greenhouse gas emissions directly and indirectly, so the building industry will be required to play a significant role in achieving this reduction.

This means we’re going to have to change the way we operate. Future approaches to construction will be driven by good design underpinned by robust scientific research. They must consider the environmental impact of the materials used, the energy efficiency and durability of buildings during their lifetimes of use and how building waste is managed at the end of their lives. This will support policies to reduce energy consumption and greenhouse gas emissions.

What is a high-performance building?

High-performance buildings are designed to perform significantly better than average.

The thermal properties of the building envelope, maintaining a comfortable indoor temperature (including avoiding overheating), good ventilation and efficient energy use are considered together to provide a building that operates effectively as a complete system. The performance of these buildings is determined as a whole, rather than by the performance of their individual components.

The small details become much more important when aiming for high performance, so aspects like the thermal bridges – routes where heat escapes most easily – are considered carefully, as well as the performance of window installation methods and ventilation systems. Airtightness is important for maximising the benefits of mechanical ventilation with heat recovery, as well as providing a draught-free and comfortable indoor environment.

These buildings will significantly exceed the requirements of the New Zealand Building Code. If properly designed and evaluated, they can maintain high levels of performance throughout their lifetimes.

High-performance buildings can provide a great quality of life for the people who use them. Their low energy requirements directly address the issue of the affordability of power bills and will reduce their greenhouse gas emissions over the lifetime of the building. These buildings should have minimal impact on the natural environment, not only for their operational emissions during their lifetimes but also for the emissions involved in building them in the first place – embodied carbon emissions.

Achieving high performance

The know-how and technology to produce high-performance buildings is available now but designing and building them requires a holistic approach, paying more attention to the small details from the design stage right through to the build.

Designing and detailing a high-performance building is not simply about adding more insulation. Three interdependent parameters must be properly considered. If one of these parameters is not well designed or built properly, the performance of the other two will not result in a high-performance building:

  • Thermal performance – the thermal envelope of the building should be designed to minimise thermal bridging and achieve a homogeneous insulation layer. This will provide a thermal performance that is far superior to that of a structure built to meet current Building Code requirements.
  • Ventilation – this must be adequate for the space. Modelling at the design stage will ensure that healthy levels of ventilation and indoor moisture are maintained across a range of different scenarios for how the building is occupied and used.
  • Heating – the building should be designed to minimise heat loss. A well-insulated building will require a small amount of heating to maintain a comfortable, steady indoor air temperature. Heating is a highly specialised area and requires professional advice on the type of heating system and its size.

There will be discussion and differences in opinion on the best way to balance the different capabilities and needs of a high-performance building. Achieving a functional high-performance building should be underpinned by robust scientific research, which is ongoing and continuing to make new discoveries. It means investigating, modelling, measuring and testing different approaches.

Looking to the future

High-performance building design is not about overengineering our buildings to meet high-performance targets. The Building Code will continue to be updated over time to reflect the need for better building performance in New Zealand. The present review of Building Code clause H1 Energy efficiency may go some way to tightening and increasing the requirements for thermal efficiency in new builds and major renovations. However, it will continue to be a minimum standard.

By designing buildings that perform as a cohesive system well above Building Code requirements, we can pave the way towards the future for New Zealand’s building stock as a whole – and support our future low-carbon economy.

But we must ensure that the availability of high-performance buildings is not limited to high-end buildings exclusively for those that can afford them. The more normalised that better performance becomes, the better the quality of life of our most vulnerable citizens. The ongoing work of agencies and advocates such as MBIE, Kāinga Ora, BRANZ, Passive House Institute New Zealand, NZGBC, the Superhome Movement and others will be key to this.

These high-performance advocates are looking towards an achievable future.

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