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Source: University of Otago

Changing the Building Code to enforce construction of highly energy-efficient housing could help New Zealand reach its 100 per cent renewable energy goal, a University of Otago-led study shows.
Associate Professor Michael Jack.
Lead author Associate Professor Michael Jack, of the Department of Physics, says substantially improving the performance of New Zealand houses will lead not only to better social and health outcomes, but reduce the cost of New Zealand’s low-carbon energy transition.
“The New Zealand Government should urgently adjust policy settings to mandate highly energy-efficient housing for new-builds and retrofits,” he says.
The study, published in Energy Policy, explores the role high-performance buildings could play in reducing the winter peaks in energy demand, largely caused by electrical heating of residential buildings.
“One of the key challenges to achieving high percentages of renewable electricity supply is the seasonal mismatch between non-dispatchable renewable supply and peaks in electricity demand.
“Most studies exploring the pathway to achieve a low carbon energy transition for New Zealand have focused on expensive supply and storage solutions to meeting winter demand peaks, ignoring the potentially important role of changing demand,” Associate Professor Jack says.
He and collaborators considered a range of scenarios of energy-efficiency standards for new and retrofit residential buildings to 2050. To provide a baseline for comparison, they assumed that under all scenarios new and retrofitted houses are heated to healthy temperatures.
The results show that rapid uptake of currently achievable best-practice standards – Passive House standards – could reduce the winter electricity peak by 75 per cent from business as usual by 2050. The reduction is so dramatic that, despite predicted growth in floor area and achieving healthy temperatures, the winter space heating peak in 2050 is less than the current peak.
Associate Professor Jack says other studies have shown building to Passive House standards leads to a relatively minor, 5 to 10 per cent increase in the capital costs, which can be recouped through energy savings alone. At present the economics of retrofitting buildings to these standards are less well understood.
“This could be a pathway to a least cost, low carbon energy transition which also provides the well-known social and health co-benefits of improved dwelling performance.”
Associate Professor Jack believes New Zealand’s current Building Code is deficient as it offers little guidance for renovations, does not specify sufficiently high insulation values in colder parts of the country, and has inadequate specifications around ventilation and air tightness.
The amount of energy used for heating in New Zealand’s houses also falls well below that of other OECD countries, even when adjusted for climate.
“Numerous studies have demonstrated that our current building code leads to chronic underheating of our houses and significant negative health consequences especially in lower socio-economic households. Improving our housing standards has the potential to address all of these issues and, on top of that, lower the cost of our low carbon energy transition.
“It is critical that we start building to these new standards now and also scale-up energy-efficiency retrofits, given the 90-year lifetime of the average house,” Associate Professor Jack says.
Publication details
The role of highly energy-efficient dwellings in enabling 100% renewable electricityM W Jack, A Mirfin, and B AndersonEnergy Policy
For more information, contact:
Associate Professor Michael JackDepartment of PhysicsUniversity of OtagoEmail michael.jack@otago.ac.nz
Ellie RowleyCommunications AdviserUniversity of OtagoMob +64 21 278 8200Email ellie.rowley@otago.ac.nz

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