i3 Sealing System

illbruck i3 provides a state-of-the-art universal sealing system for the perimeter sealing of windows, that seals OUT weather while sealing IN comfort and energy savings.


i3 is an externally weatherproof system, which also prohibits the formation of condensation and prevents thermal bridging around the frame. This is a problem that can lead to a reduction in the level of thermal insulation, damage to building components and mould formation, and importantly compromise the benefits of a very energy efficient window or door. The high expense of an A++ (BFRC Window Energy Rating) or low U-value, eg 1.2 W/m².K can be enhanced by a highly effective sealing system.

Why do I need a BBA accredited i3 system?

As building regulations change, new solutions and practices are required. In June 2022, Approved Document L (ADL) was amended with more stringent energy saving measures in mind as the UK moves towards achieving net zero emissions by 2050.

Air permeability targets have become more onerous with the effect that ADL now recommends the use of airtight tapes and membranes to seal around windows and doors.

The innovative i3 system encompasses the concept of sealing out weather whilst sealing in comfort and energy savings and has BBA accreditation and a 10 year warranty which provides assurance of performance for the builder and warranty provider.

By selecting the appropriate products, a simple, cost effective installation will benefit the building owner / occupier for years to come and lead to greater comfort and lower heating costs.

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The i3 Window Sealing System How it works: “inside tighter than outside”

Proper sealing is an effective interaction of the outer, middle, and inner sealing levels on the principle of “inside tighter than outside.” By selecting appropriate products from our seven system components, various combinations can be created to suit the installation situation. The resulting system will meet all the requirements of modern sealing conventions.

The result: An externally weatherproof but vapour permeable system, which also prohibits the warm internal air penetrating the joint and forming condensation, a problem which can lead to a reduction in the level of thermal insulation, damage to building components and mould formation.

a) Exceeds 600 Pa as per DIN EN 1027 Imperviousness to Driving Rain and DIN 18542 (testing of sealing of outside wall joints with impregnated sealing tapes).

b) Effective filling and insulation of the window joint seal.

c) Airtight to UK Building Regulations Document L and DIN 18542 & DIN EN 1026 (testing window and door air permeability). Also meets Passive House airtightness requirements.

10-year i3 performance guarantee*

The i3 Window Sealing System from illbruck comes with a 10-year guarantee* for the performance of the joints.

* Under the conditions specified - contact us for more details.

BBA Accreditation

The i3 system and its individual components are BBA approved, proving their fitness for purpose.  Download our BBA certification from our Download Centre.