Sustainable retrofit on a fixed budget

This Issue This is a part of the Retrofit and renovation feature

, Build 116

A retrofit of a 1950s state house was a winner at the inaugural Sustainable Habitat Challenge awards. This renovation offers lessons for others with similar projects.

Walls were removed and the house opened up for better flow.
Walls were removed and the house opened up for better flow.
New bedroom with ventilator.
The 1950s state house in Tamaki with rainwater tank and hot water heat pump.
R2.6 insulation was added to walls.

When Team Housewise rose to the Sustainable Habitat Challenge, it was keen to demonstrate sustainable design on a fixed budget in retrofitting a classic 1950s state house. The team comprised members from Housing New Zealand, the University of Auckland, the New Zealand Housing Foundation and Landcare Research.

Judges were impressed with the collaborative process and level of detail in the $100,000 renovation of a Housing New Zealand home, which included a raft of energy-saving features designed to improve the health and wellbeing of the tenant family.

Sustainable, repeatable package

Team Housewise was interested in developing a sustainable renovation/retrofit package using commonly available and easily deployed technologies. The team also wanted a collaborative process involving the tenant family to help develop a more sustainable way of living. Housing New Zealand had two important additional design criteria – repeatability and monitoring to see how the interventions performed and their effects on the tenant family.

A normal upgrade package costs around $60,000. Typically, this covers replacing bathrooms and kitchens and insulating ceilings and floors. Team Housewise had a budget of $100,000 to explore whether it was possible to go further in renovating a home to be energy-efficient and health-enhancing.

The project wanted to consider what kind of long-term return taxpayers might see on this investment in terms of the lifespan of the house, the health of the tenants and the reduction in carbon footprint.

For the tenant family, a primary consideration was operational affordability and the team tried to include designs and technologies that would minimise additional operating costs and were relatively easy to use.

New bedroom with ventilator.

Extensive renovation needed

The house presented most of the chronic symptoms associated with underperforming housing stock from its era: damp and mouldy, yet still draughty; too cold in winter; too hot in summer. It was a building in need of extensive maintenance and design modification.

The team felt it was essential to engage the family in the design process to build awareness and capacity to manage the operational decisions involved in balancing energy and water cost savings with comfort and health improvements.

Combining features of the house with the Sustainable Habitat Challenge criteria, Team Housewise’s aims and the tenant family’s needs, the objectives of the retrofit design were to:

  • improve the health of the tenant family
  • improve the useability and spatial configuration of the house to better suit the needs of the family
  • improve passive solar design features
  • improve the average indoor air temperature
  • improve thermal performance of the building envelope
  • reduce condensation and improve ventilation, both passive and active
  • improve energy and water use efficiency and reduce energy and water consumption
  • improve the family’s control over both comfort and operational costs
  • mitigate problems caused by poor stormwater drainage on site
  • use the project to develop and enhance each team member’s individual organisational learnings about sustainable design and living.
The 1950s state house in Tamaki with rainwater tank and hot water heat pump.

Internal layout changes

The original layout was not suitable for a growing family so the design was reconfigured to resolve these issues, while also capturing passive solar benefits. These changes included:

  • removing a fireplace and a wall to the sunroom to open up the lounge
  • opening up the lounge to the kitchen
  • adding opening doors from the lounge to a north-facing deck
  • adding a new bedroom within the existing floor area
  • creating a separate toilet
  • creating a separate shower
  • new wardrobes and storage areas
  • new kitchen with windows to the yard space to view children playing
  • removal of old asbestos flooring.

Energy efficiency changes

Team Housewise’s vision was to halve the family’s annual energy use, from an estimated 10,000 kWh/year to 5,000 kWh/year, by improving the insulation of the building envelope, installing energy-efficient heating, reconfiguring the house to better utilise the sun’s energy and operating the house accordingly.

At the same time, the team aimed to improve indoor air temperature of the house and eliminate draughts and excessive condensation.

Energy-saving features included:

  • R3.2 underfloor insulation
  • R2.6 wall insulation
  • additional ceiling insulation over R5
  • removal of an inefficient fireplace
  • new external hot water heat pump
  • lined thermal drapes under pelmets for all windows and doors
  • installation of a 2.4 kWh electric resistance heater
  • energy-efficient lighting – compact fluorescent bulbs
  • low-flow showerhead, taps and dual flush toilet
  • large rainwater tank to collect roof run-off to flush toilets and for external use.

Many positive outcomes

The house increased its Home Energy Rating from 2 to 5 stars. Key achievements from this project were:

  • a warmer, drier, better ventilated home with enhanced solar passive input
  • improved section/property with better access from house to yard via a new deck
  • resident-friendly living spaces and common areas and improved storage
  • the addition of a full size single bedroom
  • introducing the tenant family to new ways of living sustainably including developing an interest in gardening
  • monitoring to gather quantitative and qualitative data on the performance of the retrofitted house and its effects on and suitability for the family
  • new relationships and improved understanding among team members of the collaborative design process and sustainable products for residential houses.

The project proved to be a real joint venture, with the involvement of the tenant family being particularly rewarding. Team Housewise hopes that the project will inspire Housing New Zealand to run similar processes on other state properties.

R2.6 insulation was added to walls.

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Walls were removed and the house opened up for better flow.
Walls were removed and the house opened up for better flow.
New bedroom with ventilator.
The 1950s state house in Tamaki with rainwater tank and hot water heat pump.
R2.6 insulation was added to walls.

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