Has the Garrett insulation scheme actually reduced the rate of installation caused fires? It’s a strange thing to say – well, it’s strange if you don’t think about it too hard. What we often forget is that Garrett’s insulation program dramatically increased standards in an industry where there were previously very few.

First off, some raw numbers. If we go fossicking over on the ABS site, we find some data about the numbers of buildings with insulation in Australia in 2008 – the year before the Garrett insulation program. We’ll use these numbers as our “before” data set.

61% of 5,218,000 dwellings – or 3,183,265 – had insulation in 2008 according to our favourite Bureau. According to Garrett’s department, there were also between 65,000 and 70,000 new installations done per year before the insulation program. Let’s split the difference and call it 67,500 installations.

We also know from Garrett’s department in the same letter than between 80 and 85 fires occurred every year because of insulation. That’s the numbers we need for the pre-Garrett program.

Moving on to the Garret program numbers, we know that during the program, 1.1 million installations were undertaken. So that’s our yearly installation rate and it pushes the number of houses currently with insulation up to 4.28 million homes.

We also know that 93 fires have been linked to the program.

There’s our “after numbers” we need to do the comparison.

With the 2008 figures on the numbers of fires, we don’t know how many of them were as a result of new installations and how many of them were caused by insulation that was already in the ceiling and may have been there for years. So what we need to do is differentiate between the fires caused by the insulation stock (the pre-existing insulation) and new installations.

To do this we’ll create three scenarios:

Scenario 1: 10% of fires were caused by existing insulation and 90% caused by new installations

Scenario 2: 50% of fires were caused by existing insulation and 50% caused by new installations

Senario 3: 90% of fires were caused by existing insulation and 10% caused by new installations

This gives us a range of all possible likely outcomes. If we measure the number of fires caused by new installs using these three scenarios for 2008, and for our known number of 93 for Garrett’s program, this is what we get.

fire3scenarios

From here, we can figure out how many fires there were per new installation in both 2008 (where there were 67,500 new installs) under it’s three scenarios, and with the Garrett program (where there was 1.1 million installs) – simply by dividing the number of installations undertaken by the number of fires attributable to new installations.

firerates3senarios

Under Scenario 1 where 90% of fires are attributable to new installations, 1 in 909 installs lead to fire. Under Scenario 2 it’s 1 in 1636 installs lead to fire while under Scenario 3 it’s 1 in 8182 installs.

Under the Garrett insulation program, the rate is 1 in 11,828 – a much smaller rate of fires than what existed before the program.

The Insulation Program Safety Multiple is simply the Garrett program rate divided by the 2008 rate – it shows how many times safer the Garrett program is compared to each of the three scenarios for 2008.

Interesting – that’s what the data says.

UPDATE:

I borked a link back up there earlier. Here’s where the 65-70K installations per year for the pre-Garrett period were mentioned by the Dept head.

http://blogs.crikey.com.au/pollytics/files/2010/02/Secretarys-opening-statement-220210.pdf

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