Multipane, insultating glazing structures having exceptional thermal insulation performance are provided. The novel multipane structures comprise two substantially parallel rigid glazing sheets spaced apart by an interior spacer of a low thermal conductivity, closed cell, foamed polymer. In a preferred embodiment, the glazing sheets are present in a four-pane structure filled with an inert gas and sealed with a gas-impermeable, continous tape overlaying a curable, high modulus sealant. Methods for manufacturing the novel glazing structures are disclosed as well.