EPS foam is an inert material, meaning it is very slow in any reaction, and there are no active properties to it. This does not mean however that mold will never propagate on an ICF wall just because it uses EPS as insulation. The truth is, if you do not have sufficient air flow, you can accumulate an excess of moisture through condensation at your openings. This build up of water, if not evaporated, will eventually cause mold to grow on the paper of the drywall. This is why, when dealing with your HVAC system, you must adjust it accordingly for a tighter building envelope, therefore requiring more air exchanges.