I hate to be the bearer of bad news, but if you are worried about water damage Icynene isn't the answer. Icynene is open cell foam--rather like a sponge. Any insulation -- any building material for that matter --that becomes saturated with water is a potential problem. Given serious water incursion due to ice damming your dad would have had the same problem with fiber glass or open cell foam. Among insulation materials the only one that isn't subject to water saturation is closed cell foam. It is extremely expensive, typically about 4X or 5X more than cellulose.