The Whole House
The Whole of Home (WOH) energy rating, introduced in the National Construction Code (NCC) 2022, represents a significant expansion of Australia's energy rating system. While previous assessments focused solely on the building shell, this new approach evaluates the comprehensive energy usage of a home, including all building services and appliances. The WOH rating considers heating, cooling, cooking appliances, hot water systems, lighting, and pool equipment.
The rating system operates on a 100-point scale, with adjustments made for energy generated by solar panels. New homes must meet an annual energy use budget, which is determined through the assessment of fixed appliances including lighting, hot water, cooling, heating, swimming pool services, and solar panel energy generation.
Annual Energy Use Assessment
To determine a home's annual energy usage, we use the Accurate software to analyse data from fixed appliances and air conditioning systems. The assessment includes several key components:
Lighting Systems: Annual lighting energy consumption is calculated by analysing typical usage patterns within each room of the home. This provides a comprehensive view of lighting-related energy requirements throughout the year.
Hot Water Systems: Energy consumption for hot water is evaluated based on the type of system and it’s efficiency rating. The assessment considers various technologies including gas, electric, heat pump, and solar thermal systems, each with different energy consumption values.
Cooling Systems: Cooling energy requirements are determined through thermal assessment of the interior spaces. The analysis accounts for the climatic conditions of where the project is located and different system types, including Heat Pump, Ducted Heat Pump, and evaporative cooling systems, each with specific energy efficiency ratings that impact overall consumption.
Heating Systems: Similar to cooling, heating energy usage is calculated through thermal assessment. The evaluation considers multiple heating technologies: Heat Pump, Ducted Heat Pump, Electric, Gas space or ducted systems, and wood heaters. The assessment factors in both the rooms serviced and the system's energy efficiency rating to determine annual energy consumption.
Swimming Pool: Systems Pool energy usage is calculated based on the pool's volume and the type of cleaning system employed. The assessment differentiates between pressure cleaners and robotic cleaners, as these systems have varying energy requirements.
Solar Photovoltaic Systems: Solar PV systems can offset the home's energy usage. The assessment considers several factors that influence energy generation, including the system's slope, size, orientation angle, and time zone location. These variables help determine the annual energy generation potential.
NatHERS Whole of Home Rating Requirements
To comply with current standards, homes must achieve both a7-star energy rating and a minimum Whole of Home rating of 60 out of 100. The final rating is calculated using the NCC's energy value metric, which incorporates three key factors:
- Energy cost to the consumer
- Impact on the energy network
- Carbon emissions associated with energy usage
This comprehensive approach connects residential design decisions to broader energy systems and environmental impacts in Australia. The NCC's energy efficiency requirements serve a dual purpose - reducing energy consumption and greenhouse emissions while enhancing occupant comfort and well-being.
A perfect score of 100 indicates a net zero energy value home, which would typically result in minimal or no energy bills for occupants. Using the Accurate software for energy usage assessment allows us to identify high-consumption systems and explore alternative solutions to reduce overall energy usage.
Reference and more information:
https://www.nathers.gov.au/whole-of-home
https://www.nathers.gov.au/resources/faqs
