Decarbonising Buildings Part 3: Is carbon actually the right metric to measure progress?
We've covered materials and smart technology. Now for the part that determines whether any of this actually scales: policy and regulation.
Individual choices matter. But buildings are a sector-wide problem, and sector-wide problems need frameworks that apply to everyone — not just the early adopters who were already going to do the right thing. That's what good policy does. It raises the floor for everybody.
The question is whether the frameworks we have — and the metrics we're using to drive them — are actually the right ones.
What good policy does well
When building regulations are well designed, they do several things at once. They push minimum standards up over time — so the worst-performing buildings get dragged towards acceptable, and the average keeps rising. They create market certainty, which encourages manufacturers and developers to invest in better products and practices, because they know the rules aren't going to change overnight. And they level the playing field — no one gets a competitive advantage by cutting corners on environmental performance if the rules prevent it.
New Zealand's H1 energy efficiency requirements are an example of this in action. Each iteration has tightened insulation and glazing minimums, and the industry has adapted. It's not perfect, and it's not fast enough, but the direction is right.
Good regulation also drives innovation. When the bar is raised, the industry finds ways to meet it — often more cheaply and efficiently than anyone predicted. The history of building standards is largely a history of the industry saying "that's impossible" and then quietly figuring it out within a few years.
Where it gets complicated
Regulation isn't a free lunch. A few honest caveats:
The upfront cost of compliance is real. Higher insulation requirements, better windows, mechanical ventilation — these add to the build cost, and that lands hardest on first-home buyers and affordable housing developers. Good policy accounts for this. Bad policy ignores it and wonders why uptake is patchy.
Over-regulation — or poorly designed regulation — can slow things down rather than speed them up. Rules that are too prescriptive leave no room for innovative solutions that achieve the same outcome a different way. The best frameworks set performance targets and let the industry work out how to meet them.
And enforcement is everything. A regulation that isn't enforced isn't a regulation — it's a suggestion. New Zealand has historically had a gap between what the Building Code requires and what actually gets built. Closing that gap matters as much as raising the standards in the first place.
Carbon as a metric — useful, but not the whole story
Carbon has become the dominant metric in building sustainability, and for good reasons. It's quantifiable. It connects directly to climate outcomes. It's internationally comparable. When you put a carbon number on a building, you can set targets, track progress, and hold people accountable.
But carbon is a simplification, and it's worth being clear about what it captures and what it misses.
- Setting clear, measurable targets
- Comparing buildings and materials objectively
- Driving the shift to renewable energy
- Communicating progress to non-specialists
- Aligning with international climate frameworks
- Biodiversity and land use impacts go unmeasured
- Water use and toxicity aren't captured
- Focuses on CO₂, often missing other greenhouse gases
- Can encourage offsetting instead of actual reduction
- Oversimplifies complex environmental trade-offs
The risk with carbon as the primary lens is greenwashing by numbers — a building that looks good on a carbon scorecard but is quietly problematic in other ways. Embodied carbon calculations in particular can be gamed by careful material selection without addressing the bigger picture of how a building performs over its lifetime.
The connection between low carbon and healthy buildings
Here's where things get interesting — and where the carbon metric earns some of its credibility back.
Buildings with low operational carbon tend to be better buildings to live in. Not as a coincidence, but as a direct consequence of how they're designed. A well-insulated, airtight building with good ventilation uses less energy for heating and cooling. But it also has more stable temperatures, better air quality, lower humidity, and less condensation risk. The things that make it energy-efficient are often the same things that make it healthier.
So while carbon isn't a perfect proxy for building quality, it's not a bad one. Pushing carbon performance up tends to drag other quality indicators with it — which is why it's a reasonable anchor for policy even if it's not the whole picture.
What this means in practice
If you're a homeowner or developer navigating this: pay attention to the regulatory direction of travel, not just the current minimums. Code compliance is the floor — the worst you're legally allowed to build. It's not a design target.
If you're thinking about a new build or a significant renovation, understand both your upfront carbon (the emissions in your materials and construction) and your operational carbon (the energy your building will use over decades). Both matter, and optimising one at the expense of the other is a mistake.
And if anyone tells you that carbon is all you need to worry about, or conversely that carbon is a distraction from what really matters — they're both partly right and mostly oversimplifying. The goal is buildings that perform well across the board: efficient, healthy, durable, and built with materials whose costs — financial and environmental — are genuinely understood.
That wraps up our three-part series on decarbonising buildings. If you missed the earlier parts, start with Part 1 on building materials.
