Findings from Papakowhai: An overview

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Now complete, the Papakowhai Renovation project offers some invaluable insights into sustainable renovations. 

Click on the links in the Continued Reading box for the results for individual houses.  House 4 withdrew from the project so has no results available.

Insulate everywhere

The houses which had the full thermal envelope insulated and efficient heating installed saved the most reticulated energy and had the most temperature improvement.

Two homes, for example, received the full treatment: the ceiling, walls and floors were fully insulated, double glazing was fitted, a layer of polythene spread on the ground beneath the house to inhibit rising damp, and an energy efficient heating source was installed. Pre- versus post-monitoring revealed that homeowners enjoyed substantial savings on their energy bills as a result of the retrofits - between 23% (2480kWh) and 33% (930kWh).  As well as cost savings, there was a dramatic shift in the mean winter temperatures in both the family areas and bedrooms, in one case rising 3.3°C and 5.5°C respectively, in the other rising 2.5°C and 2.9°C.

Other homes received a more modest thermal makeover, with efforts centred largely on ceiling and underfloor insulation. While these upgrades did result in energy savings and temperature improvements, not one of these homes had a healthy mean minimum temperature in the depths of winter.

The lesson from these houses is not only to install high levels of insulation as a basic first step to a warm home, but when a house already has some insulation, use money to add insulation in un-insulated areas before topping up existing insulation. The study highlighted the need for wall insulation to achieve good reticulated energy savings and healthy indoor temperatures. It needs to be promoted as a ‘must have’ retrofit solution, rather than the current perception of it being a ‘nice to do’. Double glazing should also be considered, particularly with glass-only retrofits or if windows need replacing.


Combine insulation with efficient heating

Results from the Papakowhai homes confirm other research findings that insulation improvements must be complemented by an efficient heating source.   Four homes received either efficient heat pumps, low emission pellet burners or low emission wood burners.  When coupled with good levels of insulation the potential exists to experience good temperature and energy efficiency gains. But to enjoy the full benefits, the technology must be used properly - success often comes down to education.

Homeowners in the Papakowhai Renovation project were given no special training in how to maximise the benefits of their sustainable renovations. This lack of knowledge was reflected by several homeowners’ decisions not to increase their heating. As a result, although they noticed some energy savings it was at the expense of temperature, which in these homes fell below the recommended minimums to maintain good health.

Warmer bedrooms

Several homes had heat transfer systems installed along with pellet burners and efficient wood burners.  Often a central heat source does not warm beyond the main living area.  Heat transfer systems or ducted heat pump systems push the warm air through to bedrooms and bathrooms ensuring an even heat through the house.  These homeowners report finding that the wood burner combined with the heat transfer system heats the whole house.

The effectiveness of such systems depends on installing correctly sized heat transfer ducts and using suitably powerful fans.


Hot water cylinder wraps are a great energy efficiency measure

In terms of value for money, hot water cylinder wraps and pipe lagging remain a fantastic investment. While cylinders ranged in age (1970s -2005), wrapping proved worthwhile in all cases, boosting efficiency between 11% and 30%. In fact, the cylinder wraps appear to be worthwhile even on modern A-grade cylinders, particularly if only low volumes of hot water are used.


Solar hot water systems can perform well, even in winter

The study also established that solar hot water systems can provide the majority of water heating needs and optimum installations will clearly deliver the best results.  The three homes with solar water installations had 55 to 70% of their hot water needs provided by solar - in winter!  Summer performance would be closer to 100%. And, for a moderate increase in cost, a wetback is very effective in combination with solar hot water.


Combine solar/instant gas hot water systems with low flow tapware

Interestingly, the study confirms that low-flow shower heads and flow restrictors should be included alongside solar/instant gas hot water systems.  With the seemingly endless supply of hot water that these systems promise, householders began taking longer showers.  Low flow devices combat this effect.

Extra value for the homeowners

Homeowners in the project valued the renovations for more than energy efficiency and warmth.  Those with double glazing and/or increased insulation were surprised at the effect of reducing noise indoors.  In particular homeowners were delighted that they could no longer hear train noise filtering up from the main trunk line.

Householders also report better family health associated with warmer winter indoor environments and, for those with solar water heating, increased access to hot water. This goes beyond health status to mental health benefits, expressed as an enormous sense of well-being derived from the warmth in particular, the reduction of noise and being able to improve their living conditions.

  • 31-May-2009 (Report TE106/18)

    Papakowhai Renovations: Project Summary and Case Studies (PDF 1.3MB)

    Lois Easton

    The Papakowhai Renovation project renovated nine homes with a range of sustainable interventions and monitored them to see the effects of the retrofits on dwelling performance.  During the course of the project, nine reports on different aspects of the project were prepared.  This report summarises these reports and presents the overall findings, with a case study for each house.

Solar panel, Papakowhai house

Solar panels provided 55-70% water heating in winter.

Insulation ready to install

The most improved temperatures and energy savings were in houses which had insulation installed in ceilings, floors and walls.

Article from InHouse

This article from InHouse magazine (Certified Builders’ Association of New Zealand) includes a case study of one of the Papakowhai homes