Building a 70m² Granny Flat Without Consent? Here's What You Need to Know About Insulation (H1 Requirements)
April 20, 2025 By Kate Martin
Big news if you're thinking about building a small home on your property—new legislation in New Zealand now allows you to build a granny flat up to 70m² without needing a building or resource consent.
This is great for families wanting to add extra space for grandparents, teenagers, or even a rental unit. But before you get too far, there's one important thing to remember:
Even if you don’t need consent, you still need to follow the Building Code—and that includes H1 energy efficiency rules.
What Is H1 and Why Does It Matter?
H1 is part of the New Zealand Building Code that focuses on energy efficiency—essentially how well your home keeps the warmth in and the cold out. It sets minimum insulation standards for different parts of a building like the roof, walls, floor, and windows.
Why it matters:
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It helps keep your space warmer in winter and cooler in summer
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It reduces your power bills
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It lowers the environmental impact of heating and cooling
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Even though your granny flat might not need consent, it must still meet these H1 insulation rules to be compliant.
What Are the Insulation Rules?
New Zealand is split into 3 climate zones. Each zone has minimum insulation levels, measured in R-values (which show how well a material resists heat loss).
The colder the climate, the higher the insulation standard.
Insulation levels are measured in R-values (resistance to heat flow). The higher the R-value, the better the insulation.
Here’s a table of minimum R-values required for a small home (under 300m²):
Real Life Example
Let’s say you’re building a 70m² unit in Auckland.
What you’ll need:
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Roof: Use R7.4 ceiling batts (exceeds the minimum R6.6)
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Walls: R2.2 wall batts are great – they meet and slightly exceed the R2.0 requirement
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Floor: Use an insulated concrete slab with R1.5 or install underfloor insulation
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Windows: Standard thermally aluminium-framed double-glazed units usually meet the minimum R0.46
This setup will ensure your flat is warm and comfortable with no risk of underperforming insulation.
But what if you don’t want to install that much insulation in the roof? Or perhaps you want to save some money on the glazing? We can help with that!
We provide a calculation or modelling service that lets you customise your building's insulation and windows. This means you can choose to spend less on things like roof insulation or windows, and we’ll help you figure out how it will still affect the overall comfort of your home.
With our method, we can adjust the insulation in different areas of your new build, while making sure your home stays warm and energy-efficient. You’ll be able to save money where it matters most without sacrificing comfort or energy savings.
What Happens if I Don’t Follow H1?
While you don’t need a consent, you’re still legally required to follow the Building Code. If your granny flat doesn’t meet these requirements:
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You may have issues when selling or insuring the property
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It might be more expensive to heat (and uncomfortable to live in)
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You could be asked to make changes later, at your cost
Getting insulation right upfront is worth the effort.
In Summary
✅ Yes, you can build a 70m² granny flat without a consent
✅ But, you still need to follow H1 energy efficiency rules
✅ Make sure your insulation meets the R-values for your climate zone
✅ Use good-quality insulation and double glazing to meet (or exceed) the standard
Building warm, dry, and energy-efficient homes benefits everyone—and future-proofs your property.
Need Help Calculating Your Insulation?
If you’re not sure what you need for your project, we can help! We offer support with H1 support and insulation advice so you can build smarter, warmer, more cost effective homes!
About the author
Kate Martin
H1 Specialist
Reshape Consulting Ltd
I have had been involved in a energy efficency and energy modelling in buildings for the the last 3 years and have worked on over 200 H1 compliance reports, building performance analysis projects, and daylight audits.
