Sawdust is no more flamable than the insulation you buy at Menards, and it may be less flamable.
The fire in the New Jersey nitclub 'The Station'
was partly because the club bought the cheapest
insulation on the market. While there is a non-flamable grade of polystyrene made, called vapor expanded, you will have a hard time buying it
unless you are a big commercial building contractor. Wood can be fireproofed with 17 percent phosphoric acid, like you get when you buy Navel Jelly. Maybe that is why it has gotten impossible to buy over the internet in gallons.
It used to be available really cheap. Now you have to buy 50 gallon drums to get a fair price.
The catch is the moisture content. Studies show that buildings made with dried leaves - not just as insulation - as the walls itself - or straw bales last long IF the relative humidity is less than 85 percent when installed and bags are used like you can get at http://www.thediode.com
If not in bags, moisture could get in and then the organic materials can 'spontaniously combust'.
Ask any farmer what that means. It's what they worry about when barns burn down. If you have sawdust in bags, and you don't want it, I'll buy
it! It's good insulation. Down south pecan shell
some say are 10 times better than any commercial product, and they mean the results of controlled tests. I'm not sure I believe it, but anyway
pecan shells cost about $30 per cubic foot to get
to north and midwest states. So, the old folks
were NOT stupid OR backward when they did this.