Prefabricated shell assembly for window trim

A shell assembly comprised of trim members for the interior surrounds of a substantially rectangular window opening, said trim members being joined together so as to form the trim facing for said window;

• each such trim member being comprised of (i) an elongated casing section having an interior surface adapted for attachment to the wall surrounding said window opening, the inner longitudinal edge of said casing section being joined with and substantially perpendicular to (ii) an elongated border section, having a length commensurate with the length of said casing section and a width of from about 1/2 to 6 inches, the interior surface of said border section being adapted for attachment to the jamb surface which is perpendicular to the plane of the wall and to the plane of the window, a major portion of said interior surface having longitudinal grooves therein, said grooves being parallel to each other and to the free longitudinal edge of said border section, and being spaced from each other a distance of about 1/8 to 1/2 inch, permitting said width readily to be modified to correspond with the depth between the wall and the window rail, so as to fit properly therebetween when said trim member is attached to the wall, wherein the border section of at least one of said side trim members has an interior surface constructed to provide at least one approximately longitudinal channel between said interior surface and said jamb surface, in which a portion of said channel near one end thereof can be connected to a source of air under a pressure greater than ambient, while another portion near the other end thereof connects to an aperture penetrating the thickness of said border section at an acute angle thereto, whereby air flowing through said channel and said aperture will be caused to flow over the inner surface of the window and prevent condensation thereon.