wallop: Maybe airfoam is a different chemical mixture compared to Expol? All the Expol bags I have used have a warning on the them about not touching cables. From what I was told the polystyrene reacts with the cables insulation eventually causing them to short out. You can wrap the cables to protect them. From the Expol website -
"For cables that come into DIRECT contact with Expol Underfloor, place Expol Wireguard around the wires before installation.".
Yep this is very important, here's the full story (PDF)