Residential Whole of Home

The 2022 edition of the National Construction Code (NCC2022) added a new Performance Requirement for Whole of Home Energy Usage in all new residential homes. For Class 1 buildings (houses and duplexes), this is NCC2022 Volume 2 Performance Requirement H6P2, and for Class 2 buildings or Class 4 part buildings (apartments) this is NCC2022 Volume 1 Performance Requirement J1P3. This is in addition to the Performance Requirement for Thermal Performance (Residential Energy Efficiency), with nominal stringency increased in NatHERS software from 6 Stars to 7 Stars.

The development of the Whole of Home (WoH) process started in 2019, with extensive industry consultation in the formation stages. By and large, the calculation process for Energy usage is pretty similar for the different residential building classes. The NCC now limits the amount of regulated energy a proposed dwelling is calculated to use according to standardised operational assumptions. So, what appliances are now being regulated?

As the Australian Government has regulated the Energy Efficiency of most appliances for several years, most common appliances are already rated for energy efficiency. You can learn more on this at the Australian government’s Energy Rating website.

Which appliances count?

Regulated appliances in WoH cover most high energy-usage equipment:

• Space heating
• Air-conditioning/cooling
• Water heating
• Pool & Spa pumps
• Solar Photovoltaics (PV) (creates an offset for energy usage)

There are two main ways to calculate the Whole of Home energy usage: the ABCB WoH Calculator, and an extension to NatHERS software. The ABCB WoH Calculator is a Deemed-to-Satisfy method & can be applied with either a DtS evaluation of building Thermal Performance, or with a NatHERS assessment of building thermal performance. The ABCB Whole of Home calculator automates the NCC Whole of Home energy usage requirements with extensive look-up tables of performance factors (Part 13.6 of the ABCB Housing Provisions and J3D14 of NCC Volume One). Dwellings smaller than 10m² or larger than 500m² can’t use the DtS calculator.

A house needs to reach 7 stars or equivalent before we can calculate the WoH. Using the DtS WoH method, the building must comply with the Thermal Performance Requirement separately. With the NatHERS WoH calculation, a high-performing building will get recognition in the WoH calculation, because of the reduced need for artificial heating and cooling. There’s also many more options available in the NatHERS WoH assessment, including more accurate efficiency of appliances, solar PV panels, batteries, the type of stove & oven, as well as lighting efficiency.

Meanwhile, there’s some limitations to DtS WoH method: Solar batteries can be counted only in NatHERS software because the software is needed to calculate their hourly impact. Artificial lighting can be counted in NatHERS software, where the average is less than 5W/m². Stoves & ovens can be counted in NatHERS software which estimates costs, energy use & emissions. Plug-loads are not regulated; an average allowance is based on the total floor area (measured inside the external walls and including any conditioned garage).

There’s no way around it – big houses use more energy. Even with high efficiency air-conditioning and water heating, large dwellings will more likely need solar PV to meet the requirements.
The energy usage allowance is related to the societal cost of energy, related to the cost of electricity (or gas) and emissions from generation (not just use).

Unless we’re supplied a detailed list of proposed appliances, we have to use low-efficiency default appliances. So it’s almost always in your best interests to include the air-conditioning, water heating and solar PV details. Pools will likely need solar PV to offset the additional energy usage from pool pumps.

If you still want to know more or have any questions, contact us for more information about Whole of Home. We have an additional Whole of Home Checklist that can help us get the right information for your project. The appliance list is most important (Manufacturer & Model No.) so we can look up the appliance efficiency, however it can vary according to location. If needed, we’ll get you to clarify what you are planning to use.

At Anderson Energy Efficiency, we’ve got you covered for all the latest developments of the National Construction Code.