There is a file data\ini\armor.ini
Anyone can balance the vulnerability of buildings... For example, you might find this text:
CODE
Armor = DEFAULT 50%
Armor = CRUSH 1%
Armor = SLASH 75%
Armor = CHOP 100%
Armor = URUK 60%
Armor = CAVALRY 55%
Armor = SPECIALIST 30%
Armor = PIERCE 1%
Armor = FLAME 100%
Armor = FROST 75%
Armor = SIEGE 150%
Armor = STRUCTURAL 25%
Armor = HERO 75%
Armor = HERO_RANGED 5%
Armor = LOGICAL_FIRE 1%
Armor = CAVALRY_RANGED 2%
End