Green Star rating calculation
Green Star rating tools award points for achievement of specific credits in each rating category, as defined in the applicable Green Star Technical Manual.
The single (overall) score of a project is determined by:
- Calculating each category score;
- Applying an environmental weighting to each category;
- Adding all weighted category scores together; and
- Adding any innovation points that may have been achieved.
A project's score is determined for each category based on the percentage of points achieved as follows:
Category Score = No. of Points Achieved / No. of Points Available x 100%
For example, if 8 energy points were achieved out of a total available of 13 then the category score would be 61.5%.
Not all credits are applicable to every project, and many credits have an 'na' option. In these instances, the points for these credits are excluded from the 'Points Available' used to calculate the category score. This prevents distortion of the category scores (up or down) for issues that are not applicable in that project or building.
A refurbished building will not have new concrete poured and therefore cannot achieve the credit for use of recycled content in structural concrete. In this case, the points are not awarded and the Points Available for this credit are excluded from the Category Score calculation.
An environmental weighting is applied to each category score (except Innovation). This balances the inherent weighting that occurs through the number of points available in any rating category.
The category weightings were derived by considering a variety of scientific and stakeholder input, including:
- The OECD Sustainable Buildings Project Report;
- Australian Greenhouse Office, Environment Australia, CSIRO, the Cooperative Research Centre for Construction, and the Commonwealth Dept. of Environment and Heritage; and
- A national survey conducted by the Green Building Council, which informed the development of the tool and assisted in assessing regional variation.
Weightings also vary by geographical location, to reflect issues of importance in each state or territory. For instance, potable water has a greater significance in South Australia than the Northern Territories, and therefore the Water category has a higher weighting in South Australia.
The weighted category score is calculated as follows:
Weighted Category Score = Category Score (%) x Weighting Factor (%) / 100
Using the same example from the Category Score above, the Weighted Category Score would be: (61.5x 25 / 100) = 15.3
The single (overall) score is determined by adding together all the weighted category scores plus any innovation points (which are not weighted) that may have been awarded. The maximum possible score for the weighted categories is 100 with an additional 5 points available for innovation.
The Green Star rating is determined by comparing the overall score with the rating scale shown below.
|One Star||10 - 19 pts|
|Two Star||20 - 29 pts|
|Three Star||30 - 44 pts|
|Four Star||45 - 59 pts Best Practice|
|Five Star||60 - 74 pts Australian Excellence|
|Six Star||75+ pts World Leadership|
The Green Building Council of Australia only certifies buildings that achieve a rating of Four, Five or Six Stars.
In This Section
- What is Green Star?Fri 15 Jun 2012
- Commercial Building Disclosure schemeTue 31 May 2011
- BackgroundWed 1 Apr 2009
- Green Star rating tool categoriesWed 1 Apr 2009
- Green Star rating calculationWed 26 Mar 2008
- Development of Green Star rating toolsThu 19 Jun 2008
- Business Benefits - Lower operating costsWed 20 May 2009
- Business Benefits - Higher return on investmentWed 20 May 2009
- Business Benefits - Greater Tenant AttractionWed 20 May 2009
- Business Benefits - Enhanced marketabilityWed 20 May 2009