A window frame insulation assembly and sealing arrangement, comprising an elongated, extruded block of foam material having a first or inner side and a second or outer side. A unitary air fin is co-extruded therewith. The air fin comprises an elongated flange of flexible foam material. The air fin and the elongated block define an elongated receiving-channel that is filled with a foam compression rod there between creating a seal for blocking air and moisture from a building in which said window frame assembly has been placed.