Residential Whole of Home

The National Construction Code (NCC 2022) introduced a new Performance Requirement for Whole of Home Energy Usage in residential buildings. For Class 1 buildings (houses and duplexes) this was NCC2022 Volume 2 Performance Requirement H6P2, and for Class 2 buildings or Class 4 part buildings (apartments) this was 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 very 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, all common appliances are rated for energy efficiency. See http://www.energyrating.gov.au.

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 and 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 cannot use the DtS Calculator.

Thermal Performance (7 stars or equivalent) needs to comply first, 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 highly-performing building will get recognition in the WoH calculation, because of the reduced need for artificial heating and cooling. There are also many more options available in the NatHERS WoH assessment, including more accurate efficiency of appliances, PV panel configuration and batteries. The type of cooktop and oven, as well as lighting W/m² can be counted in the NatHERS WoH assessment method.

There are some limitations to DtS WoH method: Solar batteries can be counted only in NatHERS software because the hourly impact can be calculated. Artificial lighting can be counted in NatHERS software, where the average is less than 5W/m². Cooktops and Ovens can be counted in NatHERS software which estimates costs, energy use and 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).

Larger dwellings will use more energy. Even with high efficiency air-conditioning and water heating, large dwellings will more likely need solar PV to offset the energy usage.
The energy usage allowance related to the societal cost of energy, related to the cost of electricity (and gas) and emissions from generation (use).

Unless we are supplied a detailed list of proposed appliances, we must use low-efficiency default appliances. It is advantageous 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.

Please 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 and Model No.). We can usually look-up the appliance efficiency, however it can vary according to location. We will get you to clarify what you are planning to use, if we need to.