Nine homes in a Porirua suburb were recently renovated to achieve greater sustainability. Monitoring continues this year to measure the results but some useful tips have already come from the project.
Tucked away in Papakowhai, a suburb of Porirua City, a retrofit project is underway. The study is dubbed the Papakowhai NOW Home® Renovation Project. It aims to provide accessible and reliable information, for builders and homeowners, on how to renovate some of our harder to retrofit homes to achieve a High Standard of Sustainability™.
Many of New Zealand’s homes are cold, damp and mouldy – especially those built before 1978 when new Building Code requirements, such as mandatory insulation, were introduced to improve housing. Such homes are often uncomfortable to live in, difficult and expensive to heat, and their occupants suffer more from colds, flu and other respiratory illnesses.
Researchers selected nine Papakowhai homes with the goal of making affordable, comfortable, attractive and sustainable improvements: greater energy and water efficiency, better quality indoor environments and less waste. Renovations exceeded the ‘minimum’ because research has found that the minimum doesn’t result in long-term energy savings or sufficient improvements in indoor temperatures to ensure homes are healthy and comfortable.
Monitoring and measuring
Before renovations began, internal conditions in the houses (such as temperature and relative humidity) were monitored for 6 months. Renovations were completed mid 2007, and monitoring will continue throughout 2008 to measure the effectiveness of the changes. Before-and-after renovation energy consumption (electricity, natural gas, solid fuel, LPG and post-renovation solar water heaters) is measured, and water use is measured in most houses.
Before renovation, temperatures in most of the homes on winter nights were below World Health Organization recommended minimums in both the main living areas and bedrooms. Notably, the preliminary post-renovation findings show a marked improvement in indoor temperatures, as well as significant reductions in electricity use in the homes with the most significant renovations.
Renovating: tips for builders
As a result of the Papakowhai project, some things stood out as being particularly successful, others less so. The following tips will be useful for anyone considering a sustainable renovation, whether you are a builder or a homeowner.
INSULATING SKILLION ROOFS
Skillion roofs were particularly common in older housing. If exposed beams remain and can be covered in, insulation can easily be installed. Doing this was one of the most successful renovations in two of the houses. The result is a significantly improved thermal envelope: warmer and drier in winter (and cheaper to keep that way) and cooler in summer.
Two methods were used: nail-plating timber below the existing roof members and battening exposed beams. Due to the reduction in thermal bridging, it is anticipated that the battening exposed beams method will perform better. If the beams are required for aesthetic (or other) reasons, then the only option to insulate skillion roofs is to re-roof, which is a major construction activity.
Insulating skillion roofs was relatively economical – around $10,000 for insulation and construction costs for a significant proportion of a house. However, the renovation was messy, and occupants had to move out while it was undertaken. Poor workmanship and finishing meant a second layer of plasterboard had to be installed over the first in one instance. Not surprisingly, it was difficult to insert recessed downlights into the double thickness (26 mm) of plasterboard.
INSTALL ‘CA-RATED’ DOWNLIGHTS
Downlights are a popular lighting option in New Zealand homes. But installing these can significantly compromise the thermal insulation of the ceiling, particularly if large areas of insulation are cleared around the light penetration or patches of insulation are removed and not replaced. Clearly, increases in the Code level of ceiling insulation are worthless if it is interrupted by such practices.
This proved a common problem in the renovated houses. In one house where R5 ceiling insulation had been installed, there were 38 downlights penetrating the ceiling of the living, kitchen and dining areas. Each had a 50–200 mm diameter uninsulated circle around it, significantly comprising the ceiling’s effective R-value.
A new Standard has recently been developed for the installation of downlights: NZS 4246: 2006 Energy efficiency – Installing insulation in residential buildings. This mandates clearances around the light depending on its type (fire rated, acoustic rated, and so on). A table in Appendix C of the Standard quantifies the effect on R-values of clearances in insulation around downlights.
That said, some downlights allow insulation to be butted directly up to them (‘closed’, ‘abutted’ or ‘CA-rated’). Although these are not commonly used, they should be – only these ensure effective insulation that meets the new Code requirements.
CHECK WATER PRESSURE
It’s important to check the water pressure at the time of installing water meters. Fitting low-flow plumbing fixtures in some homes proved difficult given the considerable variation in the mains delivery of reticulated water in the hilly suburb. In some instances, pressure reducers were needed in the water supply system. These would have best been installed beside the water meters at the time of their installation, rather than afterwards, as happened during the Papakowhai project because pressure was not recorded at the time of installation.
FOLLOW THE NATURAL ORDER
When undertaking renovations, follow a logical order to obtain the best results. For budget and practical reasons, the largest and most extensive interventions should be done first. For example, solar hot water, low-emission wood/ pellet burners, mechanical ventilation and heat transfer systems should be dealt with before items such as ceiling and underfloor insulation. The latter are best left until after tradespeople have worked in the areas, to avoid any damage or removal of the insulation.
Beacon Pathway and BRANZ Ltd acknowledge the following supporters to the project: Energy Smart, Hutt Mana Charitable Trust, Porirua City Council, Azzuro Solar, Metro GlassTech, Fletcher Aluminium, Winstone Wallboards, Tasman Insulation, Rinnai New Zealand and Fisher Windows.
Articles are correct at the time of publication but may have since become outdated.