The cost of heatwaves

Heatwave vulnerability in Victoria

Heat waves have caused more deaths in Australia in the past 200 years than any other natural hazard. The 2009 heatwave alone caused over 1000 emergency department presentations, and 374 excess deaths in Victoria.

Most of the heat stress took place within the victims’ own homes, and their deaths occurred 1-2 days after the hottest period, indicating that it was the prolonged exposure to heat that causes illness.

A study by Alam, Sanjayan et al. (2016) used thermal modeling to simulate the 2009 Melbourne heatwave, and the results were alarming. During a three-day heatwave period, residents of older homes with a 0.9 Star energy rating were exposed to extreme heat stress for nearly 25 hours, compared to just 6 hours for those in a 5.4 Star-rated home.

Their simulations found that if the average house energy rating was raised from 0.9 Stars to 1.8 Stars, deaths could have been reduced to 240, and that if the energy rating was raised again to 5.4 stars as few as 37 people may have died.

The quality of our homes

A 2014 study from Sustainability Victoria measured existing homes’ energy ratings and found that approximately 20% of Victorian homes have a Star rating of 1 or below. This equates to over 300,000 existing houses and 780,000 Victorians vulnerable to extreme heat and cold stress. 

The research also found a strong trendline between the age of the building and its energy rating. It was not until 1991 that the mandatory insulation was introduced to the building code and the vast majority of houses constructed prior to then were found to have an energy rating of 3 Stars or below.

Room for Improvement

Another study from Sustainability Victoria in 2016 looked at the value of various building upgrades. They found that the average cost of upgrading the existing building fabric from 1.8 Stars to 5 Stars varied between $11,405 and $24,742. Some upgrades such as ceiling insulation and draft sealing were found to pay for themselves in as little as 4 – 6 years, the proverbial low hanging fruit for energy savings. If the entire suite of improvements was implemented to bring all pre-2005 houses above 5 Stars, the state of Victoria would save approximately $1.5 billion dollars per year in energy bill savings and prevent 5,200,000 tonnes of Greenhouse Gas emissions.

You can find the original studies here:

https://www.sustainability.vic.gov.au/About-us/Publicationshttps:

//www.sciencedirect.com/science/article/abs/pii/S2210670716300063