It's one of the most common questions we're asked: "Do I need a NatHERS assessment or a Section J report?" The answer almost always comes down to one thing — the class of building you're constructing under the National Construction Code (NCC). Here's how to tell which pathway applies.
The quick answer
As a rule of thumb: NatHERS is for homes, Section J is for commercial buildings. NatHERS rates the thermal performance of individual dwellings, while Section J sets the energy-efficiency requirements for commercial and non-residential buildings. Which one you need is decided by your building's NCC classification.
In one line
Houses and apartments (Class 1 & Class 2 dwellings) → NatHERS. Offices, shops, warehouses, hotels and the like (Class 3, 5–9) → Section J.
What NatHERS covers
NatHERS — the Nationwide House Energy Rating Scheme — models how well a dwelling holds a comfortable temperature without mechanical heating and cooling, and gives it a star rating out of 10. It's the pathway for:
- Class 1a — detached houses, townhouses and terraces.
- Class 2 — apartments (each sole-occupancy unit is rated).
- Since NCC 2022, a NatHERS assessment also includes a Whole of Home score covering fixed appliances and solar.
What Section J covers
Section J of the NCC (Volume One) sets the energy-efficiency provisions for commercial and non-residential buildings. It assesses the whole building's systems rather than just thermal comfort:
- Building fabric and envelope — walls, roof, floors and glazing.
- Air-conditioning and mechanical ventilation.
- Artificial lighting and power.
- Hot water, and (under NCC 2025) on-site solar in many cases.
It applies to building classes such as Class 3 (hotels, boarding houses), Class 5 (offices), Class 6 (shops, cafés), Class 7 (car parks, warehouses), Class 8 (factories) and Class 9 (health, aged care, assembly).
The grey area: apartments and mixed-use
This is where it gets nuanced. In a Class 2 apartment building, the individual units are typically rated under NatHERS, while the common areas and shared services (lobbies, corridors, car parks, central plant) fall under Section J. A mixed-use building with shops below and apartments above will often need both assessments.
| Your project | Assessment pathway |
|---|---|
| New house / townhouse (Class 1a) | NatHERS |
| Apartment units (Class 2) | NatHERS (per unit) |
| Apartment common areas | Section J |
| Office, shop, warehouse (Class 5–8) | Section J |
| Hotel / motel / aged care (Class 3, 9) | Section J |
| Mixed-use (shops + apartments) | Both |
Why it matters at DA stage
Getting the pathway right early saves time and money. Section J in particular is best resolved in design — glazing, insulation and services decisions are far cheaper to adjust on paper than after documentation is locked in. If your building could go either way, a quick conversation before lodgement avoids a scramble later.
Not sure which one you need?
Tell us your building class and we'll confirm the right pathway — and handle the NatHERS or Section J assessment either way. Get in touch for clear, plain-English advice.
Every project is a little different, especially mixed-use and multi-residential builds. If you'd like certainty for your specific development, our accredited assessors are happy to point you in the right direction.
