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Frequently Asked Questions

Environmentally sustainable buildings and energy rating questions answered

Energy Rating legislation and the what, how, why, who, where and when of it is very confusing to many. Let alone that the answers are often different across the different states of Australia.

So, we have provided some simple answers to some of our most frequently asked questions regarding designing environmentally sustainable buildings, energy ratings and building thermal performance assessments.

Simply put an energy rating measures the energy efficiency of the building fabric (Floor, Walls, Roof and all of their components), of a building. An energy rating is site and design specific; it takes into account the thermal efficiency of the construction materials, overshadowing caused by adjacent developments and from the building shape, then by allocating a point score for various design features a rating from 0 to 6 stars is obtained. Given standard occupancy conditions the star rating shows the potential of the house design to have low energy requirements for heating and cooling. The point score itself shows the percentage difference in energy use relative to a house located in the same climate zone which scores 0 points. A score of 19 points therefore represents 19% lower energy use relative to a 0 point house, while a -10 point score represents 10% higher energy use relative to a 0 point house.

NatHERS (Nationwide House Energy Rating Software) is a sophisticated simulation program developed by the CSIRO, the rating result is based on a detailed simulation of the house using hourly weather data. It is used exclusively for ratings in NSW. It is also used in Victoria and other states for projects which exceed the design parameters of FirstRate.

AccuRate is the next version of NatHERS, it is currently undergoing pre release testing; a release date has not been issued at this stage.

FirstRate is a correlation program developed by Sustainable Energy Authority of Victoria (SEAV). The software wasdeveloped by correlating the energy use predictions of NatHERS with building element properties. Using a test set of 55000 ratings in 20 climate zones; FirstRate provides results within 6% of Nathers 99% of the time and within 2% in 88% of tests. FirstRate is used in Victoria, Tasmania, South Australia and Western Australia as the primary rating software with NatHERS being used when the house plans exceed the design parameters of FirstRate. There is a high possibility that FirstRate will be rewritten to become a simulation program over the next 2-3 years.

BERS (Building Energy Rating Scheme) is a computer program used to simulate and analyse the thermal performance of house designs in climates ranging from Alpine to Tropical. It is used primarily for ratings in Queensland Tropical and Sub tropical climate zones.

An energy rating is required for the building permit application. It is preferable that the energy rating be commissioned prior to the final documentation being completed. This then allows for the energy rating details to be incorporated into the final version of the plans or building specification.

In Victoria the energy rating must be assessed by an energy rater accredited by the Sustainable Energy Authority Victoria (SEAV) in the use of FirstRate and/or NatHERS software.

A builder can elect to use either

  • The “Performance Provisions” of BCA Part 2.6 and obtain an energy rating from an accredited energy rater using FirstRate, NatHERS or BERS energy rating software.
  • The complex “Deemed-To-Satisfy Provisions” of BCA Volume 2 Part 3.12

It is the Energy Raters responsibility to ensure that the energy rating details align with the plans and building specification also to stamp and sign the building permit application plans for compliance. It is the builders’ responsibility to ensure that the conditions of the building permit have been complied with. To assist the builder we issue a compliance form, for the builder to sign and give to the building surveyor that all of the energy rating conditions have been met.

The Building Surveyor may also require additional inspections to ensure compliance.

Nationally, Energy Efficiency requirements are called up in the Building Code of Australia these requirements for home energy ratings are further detailed in the State additions. Subsequently they differ from state to state with Victoria having the most stringent requirements.

Floyd Group Pty Ltd

31/513-515 Maroondah Highway
Ringwood, Vic. 3134
Ph: +61 3 8870 5000

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