CALCIUM CHLORIDE,AND SNOW RAKES---YOU NEED TO ADD THE INSULATION,AND VENTING TO KEEP THE HEAT AWAY FROM THE BOTTOM of the roof,as far as soffit area venting,I drilled large 3" holes thru the existing fascia,added wood blocks over rafters for nailers,padded between with cobra vent,then installed new fascia over it,and capped it with aluminum

afterwards We cap the fascia,and aluminum cover with 3x3" backflashing that goes down below where the gutter will mount like this :

and then secure the gutter on top of the flashing,I also like to seal the back of the gutter to the 3x3 with Geocell tri-polymer sealant-I`m in Rockland county,deal with Ice dams all the time
__________________