Installation of ISO BLOCO -One onto pvc frame. ISO-BLOCO ONE The ingenious 3-in-1 solution for 100 % joint airtightness Where three products used to be required, one is now enough: ISO-BLOCO ONE. The multi-functional joint sealing tape with outstanding three-level functionality is 100 % air tight and vapour-resistant on the inside, provides thermal and sound insulation in the centre and more than 1,000 Pa resistance to driving rain on the outside.