29 June 2008
House energy star ratings - what do they mean?
Many of you may be aware that the energy efficiency of new houses is measured using a star rating system. This system has existed for a number of years and rates houses on their energy consumption from one star at the lowest level through to ten stars at the highest. But what do these rating mean in reality for you, the consumer, home purchaser or new home builder?
NatHERS, or The National Home Energy Rating System, has a great on line description of each star rating in each locality in Australia, and what it means in terms of anticipated energy consumption in a house for heating and cooling.
For example in Sydney East, a 1 star rated house will use 230MJ/m2 and a 10 star house will use 6MJ/m2. This equates to the 10 star house using only 3% of the energy of a 1 star house or being 38 times more energy efficient than the 1 star house.
Something else to be aware of is that the ratings are not linear from the 1 star through to the 10 star. A 5 star rated house does not use half of the the energy of a 1 star house, 115MJ/m2, but only uses 50MJ/m2.
This is invaluable information for anyone trying to find their way through the maze of energy stars and ratings.