All building codes in the USA and Canada specify that plastic insulation (EPS) must be covered by a thermal barrier equivalent to 15 minutes of fire protection in habitable spaces. This is achieved with ½” gypsum board or an equivalent material. Fox Blocks has specific fire testing that proves regular ½” gypsum board with regular drywall screws fastened into the plastic webs remains on the wall for the required 15-minute time period.
All ICF walls below grade, that have habitable space on one side (basement), must have a waterproofing / dampproofing membrane installed. For walls that do not have habitable space on one side (crawl space, frost walls, etc.) the EPS can be left exposed to the earth. The EPS will not deteriorate when exposed to the earth.