All of the best currently available insulation products rely on air as the magic ingredient that slows the passage of heat in or out.
You cannot stop heat from escaping/arriving, only slow it down.
Polystyrene is one of the cheapest insulation's and the most effective inch for inch.
Polystyrene is 98% air and 2% plastic.
It can be sprayed in, to create a monolithic structure, that stops heat escaping/arriving through cracks and holes in a building.
You can load things onto polystyrene, it doesn't compress, it is water proof.
Cotton is not a good insulation, heat travels by conduction through the fabric, think of wearing jeans on a hot summers day.
Trying to bulk up cotton, to increase its air content fails in the medium term as the cotton fabric is fighting a loosing battle with gravity.
Eventually gravity wins, the fabric compresses and becomes useless.