Abstract: An insulating spacer for creating a thermally insulating bridge between spaced apart panes of a multiple pane window unit comprises in one embodiment, a solid fiber-stabilized aerogel insulation material, hardened with a desiccant-impregnated hot melt adhesive. The spacer defines a thermally insulated space between the panes. Several embodiments of the insulating spacer of the present invention are disclosed. Insulated glass units using the disclosed insulating spacers and windows employing these insulated glass units have significantly better thermal performance than prior art insulated glass units and windows.