The recent revisions to the Building Code deal well with reducing heat loss in houses, but they fail to deal with overheating and the potential explosion in the use of heat pumps
Comment: The call by certain elements of the construction sector to hold back on the proposed energy efficiency changes in the New Zealand Building Code does feel like we have been here before.
The Master Builders Association, the Certified Builders Association and the National Party are asking for the changes, which are due to be phased in from November, to be slowed down because of issues of cost, industry skills and product supply.
Perhaps unsurprisingly, industry organisations were also opposed to earlier improvements in new house energy efficiency. However, National has shown more enthusiasm: thermal insulation was first required in 1978 by the third National government; in 1992, requirements were included in the New Zealand Building Code (NZBC) by the fourth National government.
The last major upgrade of this code was in 2006. There have been no real changes to the energy efficiency requirements for houses since then, other than lighting energy use changes for non-residential buildings. Yet there have been many other changes in the way we build and use our buildings. There have also been changes in the price of energy.
The recent revisions to the code, while not perfect, go some way to fixing current shortfalls. For too long, our houses have punished us if we try to keep warm: the money and heat just disappear. We need to take energy efficiency seriously if buildings are to help us not only improve health but also reduce greenhouse gas emissions.
What the changes do
The latest revisions divide New Zealand into six climate zones (there were previously three), making simple comparisons rather complex. Just looking at Auckland, Wellington, Christchurch and Dunedin, the required roof thermal resistance (R-value) has slightly more than doubled (in most roofs, this should not be a construction issue).
Wall requirements have increased slightly but these are achievable within the current construction methods. The floor requirements recognise the different performance of concrete slab-on-ground versus suspended floors, requiring a small increase for slab-on-ground and a doubling of the thermal performance for suspended floors.
Whether roof, wall or floor, different thermal insulation products will now be required. In all cases, greater care will also be required in the installation of the insulation product. The required R-value for new builds is for the overall thermal resistance of the roof, wall or floor, which includes the thermal insulation as well as the other parts, such as timber framing, interior lining, and exterior cladding.
What’s missing?
The 2022 changes deal well with reducing heat loss in houses, but they fail to deal with overheating and the potential explosion in the use of heat pumps (or air conditioners as they were once called) to reduce summer temperatures.
And there’s still no evidence-based energy efficiency requirements for apartments or other medium-density housing.
Another downside for all users is the change from a single NZBC document and three key standards to five NZBC documents and one standard, significantly increasing the complexity of matching requirement to situation.
Why it matters
Improved house energy efficiency does not just reduce the cost of heating, it reduces the need to create the by-products of heating, such as particulates and greenhouse gas emissions from fossil fuels. It also reduces the need for wood burning, which even in high-efficiency burners can lead to air-quality issues in many parts of New Zealand.
The stark reality is that with the increased dwelling construction underway, almost all the buildings in which people will live and work in 2050 are already built.
As a nation we need to do something about these existing buildings.
The healthy homes standards, introduced for rental accommodation, provide one way to think about these existing buildings. The many complaints about poor quality rental accommodation have led to minimum standards that many owner-occupied houses do not achieve. Fixing this problem needs to be on the agenda too.
