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Why do you need your house extension to be energy rated?Why do you need your house extension to be energy rated?
Why do you need your house extension to be energy rated?Why do you need your house extension to be energy rated?

Why do you need your house extension to be energy rated?

Why do you need your house extension to be energy rated?

See all articlesOutside of a home with a new second storey extension
Building Advice
Supa Group
Supa Group
January 16, 2016
January 16, 2016
minute read

Energy rating of homes has been around for a while. It’s a compulsory scheme that calculates the energy efficiency of a house design. The higher the “R” rating or a product, the more energy efficient the building will be. The R rating is a measure of thermal resistance. It’s a bit like the energy rating you see on new electrical appliances, the greater the number of stars equates to higher thermal efficiency.

The purpose of the scheme is to reduce energy consumption of the nation as a whole. The by-product is better design of your home and while the initial cost to build may be higher (although not necessarily!) there is a payoff in cheaper electricity and gas bills in the longer term and also greater comfort within the home.

The maximum rating that can be achieved is 9 stars. Due to climactic variations across Australian this can only be achieved in Sydney. The maximum that can be achieved in Melbourne is 8 stars. All house extensions and new home builds in Melbourne need to achieve a minimum standard of 6 stars by law.

The scheme is governed by NatHERS – The National House Energy Rating Scheme, which was introduced in 1993. It is a national body under the Department of Industry, Innovation and Science that regulates how homes are rated for their thermal performance. The 6 star energy rating was introduced from 1st May 2011, and all new home builds and extensions have to comply with this new requirement.

Before a permit is issued for any building works (whether a new home or a house extension) an assessment has to take place by a qualified energy assessor. This happens during the planning phase of the new home or extension and the building surveyor needs the report prior to issuing a building permit.

If you are thinking of doing a home renovation, factor in making improvements that increase your home’s “R” rating.

How do you achieve these stars?

Passive Design

We design your new home or house extension to take advantage of specific site features and your climate zone. Melbourne is in the Mild Temperate Zone. Understanding orientation and the path of the sun is really important and care needs to be taken in room and window placement and eave design as the sun is higher during summer than winter.


Use of retractable blinds, eaves and surrounding vegetation. Use deciduous species if plants are near your house, as they will shade in summer but allow sunlight through in winter. Make sure any plants near your house do not have aggressive root systems.


Rendered polystyrene cladding adds to the insulation factor of your walls in addition to other insulation added to wall cavities. There are improvements across the board that can be made including window and cladding selections that have higher energy ratings.


Consider the use of renewable energy for electricity and hot water, such as solar panels.


Reduce your overall water consumption by using water efficient appliances and capturing rainwater. This rainwater can be used in toilets or in the garden. Consider a grey water system to irrigate your garden.

The basic things you can do when building a new home or extension are:

  • Insulate your ceiling, walls and floor - remove old fashioned and ineffective blow in insulation and replace with new higher rated insulation batts. Caution should be exercised as some blow in products contain asbestos or fibreglass so understand what you are dealing with before you do anything.
  • Make sure insulation and sisalation is installed correctly leaving appropriate air pockets - seal all gaps and cracks in the existing home, and when the extension is being built. This is generally tape sealing around windows and doors, or making sure they are fitted correctly.
  • Consider retrofitting windows and doors with Low-e or insulated (double glazed) glass that achieves a higher rating.
  • Review window shading including internal and external blinds.

A home with a high star rating will be more efficient and comfortable to live in and will help reduce the running costs of your house and greenhouse gas emissions. It also goes a long way to helping the household budget and is better for the planet.

[free_consultation]Our Supa Group Design Consultants are experienced at incorporating energy efficient designs in the planning of your extension. Get in touch to learn more.


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