INSULATING GLASS UNITS

The specification describes and claims an insulating glass unit and a process for making. The unit comprises two glass panes spaced apart by a spacer of thermoplastics material adherent to the panes, an inert or heavy gas trapped within the unit and a layer of silicone elastomer located at the periphery of the unit between edge portions of the glass panes and in contact with external surfaces of the spacer. The thermoplastics material has a water vapour permeability of not more than about 0.2 l/m2/day (measured at 20.degree.C for 4mm thickness) and a shear strength of more than 0.2 MPa as determined at a sealant thickness of 0.5 mm at 23.degree.C and a shear speed of 100 mm/min. The process described for making these units comprises providing between two glass panes an endless strip of the thermoplastics material in a plastic state applied as a hot melt containing a dehydrating material, urging the two glass panes towards each other against the thermoplastics material to form a spacer comprising the thermoplastics material adherent to the panes, introducing to the cavity defined by the two panes and the spacer an inert or heavy gas and applying a layer of silicone elastomer located at the periphery of the unit in contact with external surfaces of the spacer.