Super-renos good for people and the planet

This Issue This is a part of the Renovations & retrofits feature

By - , Build 186

Deep-dive renovations on sub-par houses is an important part of how Aotearoa New Zealand can meet low-carbon goals. The result is homes that are healthier for people, less demanding on the environment and more energy efficient.

WE HAVE RECENTLY been involved in a variety of renovation projects employing some innovative strategies.

These included a 1906 villa, a typical 1980s brick veneer home and an earthquake repair and eco upgrade of a modern three-level hillside home built in 2007 on the Port Hills of Christchurch.

Prioritising healthier living and comfort

What all these renovations share is that improved comfort, internal air quality and thermal performance were prioritised for healthier living environments. There was less use of resources and reduced impact on the environment.

Owners often have different priorities when renovating. Commonly, it’s a new kitchen or bathroom and bling – new finishes or fittings to improve appearances.

Less common are performance upgrades for improved internal environment quality for health and comfort. These can be doubly beneficial. Many of the same improvements that provide for better health and comfort also result in lower energy use and a future-proofed, more environmentally sound building that reduces climate impact.

The annual Superhome Movement tours were held recently for the fifth time, show-casing homes nationwide that included renovations completed to Superhome Healthy Home Design Guide recommendations – see

Too many sub-par new homes

When discussing renovations with homeowners, one of the first questions I ask is, ‘How old is your home?’ When the answer is 2 or 3 years and people want to know how to retrofit for improve thermal efficiency and comfort, we have big problems with how we are currently building homes.

The Superhome Movement initially focused on new homes designed and built to a superior level than the sub-par Building Code minimums. Now, attention is widening to superrenos – deep-retrofit low-carbon renovations.

Renovations needed to upgrade houses

Feedback from homeowners highlight some issues, but there are also hidden problems. Even a new home built to the Building Code can have single-digit internal room temperatures and still produce over five times the carbon emissions required to meet the Paris Agreement. See Design to cut carbon now (Build 177) by Dr Dave Dowdell, BRANZ Principal Scientist Sustainability.

We can’t solve the climate crisis and biodiversity emergency by only building better new buildings. It is essential that we fix existing building stock too.

Participants in the Superhome Movement recognise the importance of upgrading New Zealand’s approximately 1 million unhealthy eco-unfriendly homes that are inefficient, difficult and expensive to heat.

Start with a holistic retrofit plan

Renovation projects are usually a lot trickier than new builds and often present unique challenges that are project specific and vary widely depending on the age and type of the building. They can be complex, and from our experience, considering everything is crucial.

Owners’ priorities and what they want to achieve will influence what approach is needed. People often don’t know what they don’t know and oversimplify things.

The budget is usually a challenge so implementing a staged holistic retrofit plan over time may be necessary. Doing part of the job won’t work. For example, only installing underfloor insulation and a top-up of ceiling insulation, as is often suggested, but nothing for windows, walls, air leakage and ventilation will not be satisfactory.

For a deep retrofit that focuses on upgrading building performance, a thorough assessment of the building must be carried out before deciding on the best interventions.

Do it properly

Our approach is to do things properly – a future-proofed planned deep retrofit over time. A shallow retrofit over the entire home usually doesn’t provide satisfactory performance and ultimately will be more expensive to properly redo later.

1906 villa

After only adding underfloor and ceiling insulation to the 1906 villa, the interior temperature of the south-facing bedrooms increased from 5°C to 7°C.

We also fitted uPVC low-E windows in the south-facing bedrooms that have no heating. We left the two north-facing living spaces for a future stage as those spaces have heat pumps and a wood fire.

1980s house

The 1980s home had its brick veneer removed. External mineral wool rigid insulation and new cladding were added, along with a warm roof consisting of more mineral wool under the metal roofing.

Triple-glazed timber-framed windows were installed and a whole-home energy recovery ventilation system with ducting fitted in the now insulated and airtight warm roof space.

Deep reno after earthquake damage

The modern hillside renovation is our own family home, which incorporated the best of both New Zealand and Japanese influences from my wife – Japanese architect, Shizuka Yasui.

When it was built in 2007, it was a hotbed of ideas reflecting design and sustainability innovations at the time, but today, we do many things differently.

Following the February 2011 Christchurch earthquake, the house was inhabitable. Repairs were delayed years due to issues The modern 2007 home was given a deep renovation when major repairs were necessary after the 2011 Christchurch earthquake. with the insurer but have now been completed, and the home is back better than ever.

The renovations include significant structural upgrades for improved resilience – we didn’t want to be waiting another 10 years after the next earthquake.

Thermal upgrades were a focus, including external insulation to walls and a warm roof to reduce thermal bridging. High-performance Warmcore triple-glazed, low-E extreme, thermally broken windows and doors were installed.

Shading devices were added for protection from overheating as well as an energy recovery balanced ventilation system, solar PV panels and rainwater harvesting and water filtering.

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Full details of these projects are available at

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