calendered side for use as a radiant barrier vacuum metallizing is a well known process in which metals are vaporized by heat and vacuum and are then deposited on the surface of a solid article from a cost performance standpoint aluminum is the preferred metal generally a typical metallization process takes place in an evacuated chamber at an absolute pressure of 0 005 to 0 010 millimeters hg the sheet passes over a number of crucibles containing molten aluminum typical process speeds are 450 to 700 feet min lower metallization speeds tend to correlate with lower emissivities but increased residence time in the chamber can damage the sheet the thickness of the deposited aluminum depends on the pressure inside the chamber temperature of the molten aluminum and surface speed of the sheet a cooled chill roll is used to back up the sheet and prevent damage from the high temperatures reached during metallization the sheet is generally metallized to a metal thickness of between 75 to 300 angstroms the metallized sheet of this invention is made from a substrate sheet having as mentioned previously high specular gloss on at least one side in order to achieve the desired emissivity and air and vapor permeability the characteristics of the substrate sheet must be carefully controlled the high specular gloss polyethylene plexifilamentary film fibril sheet of this invention has a specular gloss.