insulating perlite plaster for exterior

Hi everyone,

We have decided finally to insulate our brick house on the exterior with reed panels that are 5cm thick and since this is not enough we want to use some kind of insulative plaster. We have an abundance of perlite in Bulgaria, so we are thinking to do a layer of perlite plaster under the reed panel and another one over it. Not sure how thick we can make it without the risk of it falling out. We are looking for a recipe for the perlite plaster. Anyone have experience with exterior wall plaster made of perlite?

Thanks,
Diana