House 3 is one of the Papakowhai Renovation project success stories. Household winter power bills for the family of five reduced by 33% with 62% saved on space heating. Average winter temperatures rose by 1.7°C and 3.8°C in living areas and bedrooms respectively, with fewer unhealthy temperatures recorded. Solar water heaters provided 55% of the family hot water in winter.
House 3 was part of Beacon Pathway's first renovation research project which 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 simply providing ceiling and underfloor insulation does not, on its own, make a home warm, dry and healthy. Rather, to recognise significant benefits the whole thermal envelope must be targeted – floor, ceiling and walls – and coupled with an efficient heating system.
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 included 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.
To improve its performance, House 3 underwent a major renovation:
double glazing was installed in new aluminium frames
insulation was fitted in the walls (R2.4 batts) and under the floor (R2 foil backed batts)
a polythene vapour barrier was installed under the floor
the skillion ceiling was lowered and insulated with R3.6 batts, and the remaining ceiling insulation was re-laid and overtopped with R2.6 blanket
a variety of heaters were replaced by an NES-compliant wood burner and a ducted heat pump system;
a solar hot water system and a newly wrapped 300L cylinder were installed
flow restrictors on the shower heads and dual-flush toilets reduced water use
a kitchen rangehood replaced a broken extraction fan.
The results speak for themselves. This family of five reduced their winter power bills by 33%, from 7,550kWh to 5,070kWh. They saved 62% on space heating costs, dropping from 2,120kWh to 810kWh despite increasing their heating to bring their house to comfortable and healthy temperatures. The impact of the extra heating was absorbed by the improvement in thermal performance of the dwelling and increased efficiency of heat source.
The solar water heater provided 55% of the family’s hot water – in winter! In summer it would be close to 100%. Again, this is despite the family enjoying longer showers and using 21% more hot water in winter. The low-flow 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.
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 flu since the renovations. What’s more, an asthmatic child needed to use an inhaler less frequently. With 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.
Read more about the Papakowhai Renovation project at: www.beaconpathway.co.nz