How are NatHERS star ratings assessed?

NatHERS is assessed through a process of thermal modelling where the proposed dwelling is modelled using NatHERS approved software. The construction type, materials, glazing, lighting and insulation are used to assess the overall annual thermal performance of the project. Climate data within the software determines the development’s total heating and cooling load throughout the year, with specific heating and cooling targets outlined by NatHERS that need to be met.

NatHERS Accredited Software is used to calculate an energy efficiency star rating and is based on expected indoor temperatures. This is assessed by assessing the project’s design, climate and household use. The tool therefore does not take electrical appliances within the dwelling into consideration, other than the air flow from the dwelling’s ceiling fans.

Develop a simulation model

A NatHERS accredited assessor will enter data into the software which will generate a simulation model of the dwelling. The simulation model will include: sizes and functions of the rooms, sizes and specification of openings, building materials/windows/products, type of construction, dwelling orientation and location.

Determining the temperature of the development

The simulation model will determine the level of heating or cooling temperature that is needed for occupants to remain comfortable within the dwelling.

Determining the need for heating and cooling systems

The NatHERS Accredited software model will determine the need for heating and cooling systems when internal temperatures fall outside of a comfortable range. This is based on assuming that occupants will open and close windows, blinds or awnings in an attempt to restore a comfortable temperature level prior to using the heating or cooling system.

Calculating a rating out of 10

Once the steps above have been completed, the total annual estimated levels of energy efficient heating and cooling are determined by a ranking out of 10 stars.

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What does a NatHERS assessment include?

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