illbruck ME500 Duo Flexible Window Membrane


Tear-proof, non-woven fleece fabric with a polyethylene copolymer film, and acrylic, self-adhesive strip and butyl adhesive strip. The membrane includes a large expansion pleat for variable joint sizes and to absorb movement.

The membrane is intended for sealing window and door frames before or after installation, being attached to the wall with butyl adhesive and to the window/ door frame with self-adhesive strip. It may also be used to provide an airtight or weathertight seal to insulated panels.

illbruck ME500 Duo Flexible Window Foil E & W are reactive membranes, with a water vapour permeability that changes depending on the humidity level within the joint, enabling the membrane to act as an airtight internal seal, and weather tight, vapour open external seal.


  • Building material class: B2 to DIN 4102.
  • Water vapour permeability (sd value): 0.3 to 20 m , depending on average atmospheric humidity.
  • Application temperature: +5 to +45ºC.
  • Airtightness: . <0.1 m³[h.m(dapa)] to EN 1026.
  • Weathertightness: > 600 Pa to EN 1027.

General information

Uniclass 2015

Pr_35_90_87_10 Butyl rubber fleece tapesPrimary


L10/75 Sealant joints

L10/810 Sealant joints

Specification data - Butyl rubber fleece tapes

Product Reference

illbruck ME500 Duo Flexible Window Membrane


60–80 mm (W version)

80–110 mm (E & W version)

110–140 mm (E & W version)

140-170 mm (E version)



illbruck ME901, ME902 Butyl and Bitumen Primer

illbruck SP525 Frame & Facade Sealant and Adhesive

Standard product features



Product Options


illbruck ME901 and ME902 Butyl & Bitumen Primer can be used to improve adhesion. All lap joints and potential air leakage paths (e.g. around window fixing brackets) must be sealed with illbruck SP 525.

Third party certifications

  • 12/4891 : Accreditation in isolation or as part of the illbruck 'i3 System'