Historic Te Puni Kōkiri House achieves 20% energy savings and double endorsement

Heritage buildings don't often lead the way when it comes to energy efficiency; but Te Puni Kōkiri House in Wellington has proved it's possible with impressive ratings under both the Green Star and NABERSNZ schemes.

The building's extensive refurbishment has achieved a 5 Green Star Office Built rating - signifying 'New Zealand excellence' in sustainable design and construction. Now, it has followed that with a 4 star 'excellent' NABERSNZ rating for energy performance.

Green Star is the rating tool that certifies New Zealand buildings' environmental aspects during design, build and fit-out; while NABERSNZ benchmarks energy performance, rating office buildings from 0 to 6 stars based on a year's energy use data.

Built in 1940, the former State Insurance building at 143 Lambton Quay was lauded at the time for its innovative wavy façade and extensive use of glass, which reflected new European architectural trends. Three floors were added in the late 1980s when Te Puni Kōkiri (the Ministry of Māori Development) moved in.

Owners Argosy completed a major retrofit of the heritage building in 2013. Originally aiming for a 4 Green Star rating, they ultimately achieved 5 Green Star partly through innovations such as ultra-efficient EC fan coils (components of an air conditioning system that can respond more quickly to users' needs, reducing energy use). It also has occupancy sensors on fan coil and fresh air controls to avoid energy waste when spaces are unoccupied. The project also surpassed the maximum Green Star benchmark for minimising construction waste, with over 90% diverted from landfill.

The NABERSNZ rating assessed the base building's operational energy use. Te Puni Kōkiri House achieved its 'excellent' energy efficiency rating (4 stars out of 6), with the help of metering, better insulation and updated equipment. The building uses 20% less energy than before the refit, and is 27% more efficient than the average for commercial offices.

Saatyesh Bhana, Argosy Property Asset Manager, said the NABERSNZ rating process had identified further energy saving opportunities, and they were undergoing fine-tuning to achieve these. "This type of long-term investment works out for everyone: it creates savings for our tenants, recycles an iconic heritage building, and adds value to our investment in the building," he said. "The prime concern was to get a result that benefits our tenants. We worked closely with Te Puni Kōkiri and we're all thrilled with the results."

David Craven, Director of Rating Tools at the New Zealand Green Building Council, said the double result demonstrated the link between a Green Star rating and good energy performance. "The steps Argosy took to get a 5 Green Star rating proved key in helping it get an excellent NABERSNZ score. Although the rating systems work in very different ways, Green Star and NABERSNZ are complementary. Now both tenants and owners can reap the benefits of lower energy costs, a better space for staff and a more sustainable building," he said.

EECA Building Energy Rating Manager Mike Frew congratulated Argosy on its ongoing commitment to energy efficiency. "This highlights the possibility of improving energy performance for any office building, not just new buildings. It's great to see that having achieved 20% energy savings, Argosy are targeting even more. This project is a great example for other building owners."

The Green Star and NABERSNZ ratings for Te Puni Kōkiri House were carried out by Patrick Arnold from eCubed Building Workshop. Peter Affleck from Norman Disney Young led the retrofit project.