The choice between an aluminium bituminous vapour barrier and a PE foil is fundamental in a roof build-up and must be carefully considered. Although both solutions can be used in certain situations, the performance differences are significant. In modern roofs and building envelopes, an aluminium bituminous vapour barrier offers clear advantages, especially in buildings with higher moisture loads.
1. Much higher vapour diffusion resistance (Sd value)
One of the main differences lies in vapour diffusion resistance.
- Aluminium bituminous vapour barriers have a very high Sd value, typically > 1,500 m.
- PE foils have a significantly lower Sd value and are, in many cases, insufficient for buildings with normal to high moisture production. They are only suitable for buildings with very limited moisture production.
For buildings such as offices, schools, hospitals, care facilities, and buildings with high occupancy, a PE foil is not suitable as a reliable vapour barrier. In practice, most buildings have a higher internal moisture load than often assumed (people, ventilation, sanitary areas, processes).
The higher the moisture production in the building, the greater the need for a vapour barrier with very high vapour tightness, and here, aluminium bituminous vapour barriers clearly perform better.
Moreover, choosing an aluminium bituminous vapour barrier allows the existing roof build-up to be retained during future renovations, even if the building function changes (e.g. conversion from storage to office space).
2. Installation quality and airtightness
PE foil
- Very thin (0.1 – 0.2 mm)
- Sensitive to tearing and perforation during installation and subsequent works
- Overlaps must be taped
- Quality of overlaps may decrease due to dust, cold, or ageing
Aluminium bituminous vapour barrier
1. Application on steel deck or wooden boards
IKO shield ALU/SA and IKO shield plus ALU/SA are reinforced with HDPE or glass fibre threads, making them much more robust and walkable on substrates such as steel deck.
Seams are self-adhesive, ensuring better airtightness.
Can serve as temporary waterproofing (approx. max. 8 weeks), which is not possible with PE foil
2. Application on concrete
IKO shield ALU 3 T/F and IKO shield ALU 4 T/F feature an aluminium-glass fleece combination, making them very stable for application on concrete
The thickness of 3 or 4 mm allows application on rougher substrates
Seams are welded, ensuring better airtightness and joint quality
Can serve as temporary waterproofing (approx. max. 12 weeks), unlike PE foil
Conclusion
While PE foils are only suitable for very simple and low-moisture applications, an aluminium bituminous vapour barrier such as IKO shield offers a structurally safer, more durable, and higher-performing solution for all roof constructions.