It’s been a year since Build last reported on the project in Papakowhai, Porirua, where nine homes were retrofitted in 2007 and monitored throughout 2008. Now complete, the study offers some valuable insights into sustainable renovations.
From the outset, the Papakowhai Renovation project aimed to provide accessible and reliable information for builders and homeowners on how to sustainably renovate, to a high standard, some of New Zealand’s more challenging homes.
Funded by Beacon Pathway, researchers from BRANZ explored the most cost-effective and easy-to-implement combinations of retrofit options and developed a cost-benefit analysis for a range of sustainable technologies in the areas of energy, water, indoor environment quality and waste.
House selection process
Papakowhai was chosen for its predominance of 1960s and 1970s housing. Its pre-insulation era homes were considered difficult to energy retrofit. The suburb’s hilly setting encouraged split-level homes, many of which are oriented to the view, not the sun. The variety of building materials and building systems, from skillion to cavity roofs, and suspended timber to uninsulated concrete floors, all added to the complexity.
Before work started, the homes were monitored for temperature, humidity and energy use. Results indicated that most homes were cold, damp or high energy consumers.
Types of renovations
Three different levels of thermal intervention were applied:
- Basic – topping up insulation in the ceiling and installing it underfloor.
- Standard – fitting heavy ceiling and underfloor insulation.
- High – fitting ceiling, floor and wall insulation, double glazing and efficient space heating.
Apart from one house that was renovated to subsidised insulation levels of the day, even the ‘basic’ renovations completed in this study exceeded standard practice for that time. Previous studies had found that achieving the minimum doesn’t result in long-term energy savings or sufficient improvements in indoor temperatures to ensure homes are healthy and comfortable.
Address full thermal envelope
Although heavy ceiling and underfloor insulation resulted in some improvement to the thermal performance, the best outcomes in both reticulated energy savings and temperature improvements came from houses where a full thermal envelope and efficient heating were installed.
For example, two homes received the full treatment: the ceiling, walls and floors were fully insulated, double glazing was fitted, a layer of polythene was 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% (2,480 kWh) and 33% (930 kWh).
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 such upgrades resulted in energy savings and temperature improvements, none of these homes achieved a healthy mean minimum temperature in the depths of winter.
Wall insulation a ‘must have’
The study highlighted the need for wall insulation to achieve good reticulated energy savings and healthy indoor temperatures. This needs to be promoted as a ‘must have’ retrofit solution, rather than its current perception as a ‘nice to do’.
Double glazing should also be considered, particularly with glass-only retrofits or if windows need replacing.
Efficient heating and education needed
The Papakowhai study results confirmed findings from earlier research: improvements to insulation must be complemented by an efficient heating source.
Four of the nine homes were fitted with an efficient heat pump, low-emission pellet burner or wood burner. 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.
Wrap hot water heating
One of the top value-for-money investments is hot water cylinder wraps and pipe lagging. Cylinders ranged in age from 1970s to 2005, and wrapping proved worthwhile in all cases, boosting efficiency by 11–30%. Cylinder wraps appear to be worthwhile even on modern A-grade cylinders, particularly if only low volumes of hot water are used, thanks to the high proportion of standing losses.
The study also established that solar hot water systems can provide most water heating needs, and optimum installations will clearly deliver the best results. The sun’s free energy provided an impressive 55–70% of the hot water needs to the three homes with solar water installations – in winter! Summer performance would drive that figure closer to 100%. And for a moderate increase in cost, a wetback is very effective if combined with solar hot water.
Low-flow showerheads 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 water devices combat this effect.
Some key lessons from this research will be covered in more detail in the next few editions of Build.
Beacon Pathway and BRANZ Ltd acknowledge the following supporters to the project: Azzuro Solar, Energy Smart, Fisher Windows, Fletcher Aluminium, Hutt Mana Charitable Trust, Metro GlassTech, Porirua City Council, Rinnai New Zealand, Tasman Insulation and Winstone Wallboards.
Articles are correct at the time of publication but may have since become outdated.