MBIE is moving towards judging new homes the way we already build them: for how they perform over a lifetime.
You can install a heat pump. You can add double-glazing to your windows. But some of the most important decisions about the efficiency and comfort of your home become very difficult to change once the house is built.
That’s why the next Building Code review matters if you’re planning a new home.
What is changing in the Building Code?
The Building Code is reviewed every three years. The next review is due in 2028. MBIE hasn’t published a final list of changes, but the direction is clear.
For years, the Code has largely focused on whether individual parts of a house meet minimum requirements. That’s changing.
MBIE is now looking at how the whole house performs – the way we at Energy Efficient Homes have been thinking about and building homes for years.
Rules changing from 27 November 2026
From this date, the old energy efficiency rules (H1) can no longer be used. Designers can no longer use a checklist to show insulation compliance. They have to calculate how the walls, roof, floor, and windows perform together.
The schedule method, the simple checklist of minimum R values, is removed. Designers must use the calculation method or computer modelling instead. The calculation method only works where windows are 40% or less of the wall area, so glassier designs need modelling.
The calculation method must also assume at least 38% of a framed wall is timber unless the designer can justify a lower figure. Timber lets heat escape far more easily than insulation does. Meanwhile, the overall level of insulation required hasn’t changed.
So here’s a brain teaser: if 38% of your wall is made from 90 mm timber with an R-value of less than 0.7, how much more insulation do you need in the other 62% of the wall to achieve a minimum wall R-value of 2?
The answer becomes much clearer when you can see the wall for yourself. At our Show Home, we have a mockup of a standard wall next to an Energy Efficient wall. Book your tour to take a look.
Whole house performance
Although MBIE hasn’t confirmed what will be changing in 2028, it has published the topics it’s working on. Several are about how a home performs as a whole: better ventilation rules, a new way to assess condensation risk, a review of the climate zones used to set insulation requirements, and checking the computer tools used to predict a home’s heating, cooling, and ventilation energy use.
Heating and cooling targets
In 2023, MBIE published a method for predicting how much heating and cooling a new home will need each year. It adds up the heat coming in (sun, people, appliances) and the heat going out (walls, roof, floor, windows, timber framing, ventilation, air leaks). It uses the local climate, the shape of the house and which way it faces, then checks the result against comfort targets: 20°C to 25°C indoors, with healthy air and humidity.
This isn’t a requirement, and MBIE hasn’t said if or when it will become one, but MBIE say that designers will need to consider these factors. This isn’t new to us – it’s where every Energy Efficient Home design starts.
Overheating: later than you’d think
A house built to today’s Code, or even the 2028 Code, may still overheat. Detailed overheating requirements aren’t expected until 2031. BRANZ found the existing Building Code permits designs likely to overheat.
So if you’re building now, don’t wait for the rules to catch up. Orientation to the sun, roof overhangs, insulation, and windows are design decisions that shape how comfortable you’ll be as temperatures rise.
Find out what this means for you
A home designed as a whole system from day one is the one least likely to need catching up when the rules change.
If you’re planning to build in Canterbury, come talk with us. We’ll explain what these upcoming Building Code changes mean for you, so you’ll know the right questions to ask when it’s time to build.
