I'm attempting to find a green and cheap insulation for the roof of a school bus conversion I am building. Kapok is easily sourced for me as it literally grows on trees.
The dimensions of the roof are approximately 40' by 8.5'.
But what is the R-value of Kapok?
Are there other cons I should be aware of?
Best Answer
As @Harper states, flammability is a problem, but can be helped by treatment, e.g. applying borates. Kapok is cellulose, so see this reference. However, the amount of fire-retardant used is ~20% by weight.
That said, kapok was the standard filler (in separate compartments) for life vests for many years.
According the the link, the R-value of cellulose is between 3.2 and 3.8 per inch.