Cork! It’s awesome. Cork bark is harvested from trees and regrows, and it’s carbon sequestering. 

I’m in Austin, TX and looking at cork as exterior thermal facade.  Amorim produces it, and it can be sourced through Cross Cabin Build if you’re in the Austin area or through Thermal Cork.

Then there’s thermal cork spray, which is applied as the most exterior layer. In addition to adding some R value (not much) and rain shedding, it looks pretty sweet, sortof like pebble dash. 

My proposed wall assembly is like this (from inside out):

Lime plaster on gypsum board + Hemp wool insulation or TimberHP batt R13 + 2 x 4 framing + Vaproshield + Cork board (40mm or so which is R5.3) + Spray Cork

Note there is no rain screen in this proposed assembly as we’re using the cork board as exterior insulation.  The cork would attach directly to the Vaproshield. Please see technical data below.

Question: Can I spray cork over the cork board. Cork is hydrophobic. Will the cork spray make it too difficult for the cork board and wall assembly to dry to the exterior? 

I found some numbers on the buyspraycork.com website about waterproofing and vapor permeability of spray cork. They also have a downloadable technical data sheet. Maybe someone can translate these a bit:

Waterproofing 0.08 kg/m2h0.5
Vapour Permeability 26.6 g/m2*d

Thank you!