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Heating, cooling and insulation

Papakowhai renovation – insulate, insulate, insulate!

Full insulation and an efficient heat source led to substantial reticulated energy savings and indoor temperature improvements.

Beacon’s Papakowhai Renovation Project in Porirua tested various combinations of energy, water and indoor environment retrofits on nine ordinary 1970s homes. The houses were monitored before and after the renovations to determine how well each house performed.

Results showed that a fully insulated home boasting an efficient heat source made substantial reticulated energy savings and indoor temperature improvements.

Renovating House 3

House 3 is one of the Papakowhai success stories. Built in the 1970s, it is typical of the split level homes in the hilly suburb, oriented to the view rather than the sun.

Additionally, insulation was not required in homes of this era, and the split levels and variety of building materials and systems – from skillion to cavity roofs, and suspended to uninsulated concrete floors – produced homes considered difficult to energy retrofit.

Man replacing window with double glazing

To improve its performance, House 3 underwent a major renovation:

  • double glazing was installed
  • insulation was fitted in the walls (R2.4 insulation) and under the floor (R2 insulation and polythene vapour barrier on the ground)
  • the skillion ceiling was lowered and insulated with R3.6 insulation, and the remaining cavity ceiling insulation was re-laid and overtopped with R2.6 blanket insulation
  • a variety of heaters were replaced by a wood burner compliant with National Environmental Standards for Air Quality and a ducted heat pump system;
  • a solar thermal hot water system and a new 300-litre cylinder with cylinder wrap replaced an undersized electric hot water cylinder
  • flow restrictors on the shower heads and dual-flush toilets reduced water use
  • a kitchen rangehood replaced a broken extraction fan.

The results

This family of five reduced their winter power bills by 33 percent. They saved 62 percent on space heating costs, despite increasing their heating to bring their house to comfortable and healthy temperatures.

House 3 winter energy use (May – September)  

PeriodSpace heating (kWh)Reticulated hot water (kWh)Total reticulated energy (kWh)
Pre-Retrofit 2,120 2,130 7,550
Post-Retrofit 810 970 <5,070

The solar water heater provided 55 percent of the family’s hot water – in winter! In summer it would be close to 100 percent. Again, this is despite the family enjoying longer showers and using 21 percent more hot water in winter. The water-efficient shower heads also helped to offset greater costs for the family.

Inside the house, the family enjoyed much warmer, healthier living. The average winter temperatures in the family room rose by 1.7°C and in the bedroom by 3.8°C. Even better, the bedroom rarely dipped below 16°C overnight and the family room rarely below 18°C in the evenings. These are the minimum temperatures recommended by the World Health Organisation for healthy living.

Benefits for the family

As for the family, the changes exceeded all their expectations. They appreciated the new warmth of the house, especially being able to use the whole house rather than huddling round the fire.

Problems with condensation and mould were eliminated and they noticed improved family health with fewer colds and viruses since the renovations. What’s more, an asthmatic child needed to use an inhaler less frequently.

With a bigger hot water cylinder and their water costing less to heat, they no longer worried about the hot water running out. And an added bonus of the double glazing was reduced noise from both inside and outside the house.

Key findings of the Papakowhai Renovation Project:

  • It’s important to insulate the full thermal envelope, including the walls if you can.
  • Efficient heating must accompany a thermal retrofit.
  • Hot water cylinder wraps are a great energy efficiency measure and should be widely applied.
  • Solar hot water systems can perform well, even in winter.
  • Water-efficient showerheads should accompany hot water conversions.
Note that this document is published by the Ministry of Business, Innovation and Employment Chief Executive as Guidance under Section 175 of the Building Act 2004. This is a guide only and, if used, does not relieve any person of the obligation to consider any matter to which the information relates according to the circumstances of the particular case.