Offsite and modular construction has revolutionised the way we build but hasn’t much changed the basic challenge of airtightness.
Factory-built modules arrive on site with controlled tolerances, yet the envelope still has to be made continuous across junctions, openings and interfaces that o amount of precision manufacturing can eliminate.
That’s where specification decisions made at the drawing stage either hold up or fall short.
The membrane is what much of this depends upon.
Specify something that requires multiple additional products to perform and you introduce risk at every joint, junction and opening. Specify well, and airtightness becomes something that’s largely built in from the start.
THE PROBLEM WITH TRADITIONAL MEMBRANES AT THE DETAILS
Most membrane specifications perform adequately on an uninterrupted wall face – the real test comes at the interfaces. Think of window reveals, door frames, floor-to-wall connections, bay projections, service penetrations and corners.
These are the points where air leakage is most likely to occur, and where the quality of the detailing has the greatest influence on whether the envelope performs as designed or falls short of the modelled figures.
A membrane that requires separate taping, priming or mechanical fixing to achieve adhesion at junctions introduces a dependency on workmanship consistency that cannot always be guaranteed. Especially when the same detail is being repeated many times across a complex build-up, or when site conditions are less than ideal.
For specifiers, the question is not simply whether a membrane performs in a test environment, but whether it performs in the real conditions of a construction programme.
A SELF-ADHESIVE MEMBRANE FOR COMPLEX ENVIRONMENTS
Proshield from Don & Low is a self-adhesive, vapour-permeable airtight membrane developed for walls and floors across a range of construction types. It bonds directly to OSB, calcium silicate board, fibre cement, gypsum board, steel, concrete and timber without primers, mechanical fixings or additional tapes.
The adhesive backing runs the full width of the membrane, which means the bond is immediate, continuous and complete from the moment it is applied.
Its three-layer construction at 270g/m² gives it the tensile strength and resilience to handle both factory-based application and on-site installation without damage during handling or construction activity. A printed alignment grid on the membrane surface supports accurate, repeatable positioning. The bold blue colour is also a practical asset during installation and inspection.
Joints, overlaps and any gaps are immediately visible, which supports quality checks in the factory and on site without any additional marking or inspection process.
CERTIFIED PERFORMANCE WHERE IT COUNTS MOST
Proshield has achieved KIWA certification, an independent verification that it performs as a genuinely airtight solution not only on flat, continuous surfaces but at edges, corners and openings.
For specifiers, that certification matters.
A product tested only on flat panels can demonstrate compliance with standard test conditions but leaves uncertainty about how it performs at the interface details that affect real-world envelope behaviour.
A complete system of compatible tapes and preformed corners supports consistent, repeatable detailing at junctions throughout the programme.
Using a single tested system rather than selecting components independently reduces the risk of incompatibility at interfaces and simplifies the specification documentation.
When it comes to projects targeting Passivhaus certification or designs working to Passivhaus principles, the level of verified, repeatable airtight performance that Proshield delivers at the details is directly relevant. Passivhaus airtightness requirements are demanding, and they are met or missed at exactly the junctions and openings the KIWA certification addresses.
PERFORMANCE CREDENTIALS THAT SUPPORT THE FULL SPECIFICATION
Proshield achieves Class W1 water resistance, the highest classification available under EN 13859-2. For projects where the membrane may be exposed for a period before cladding or overcladding is complete, that level of temporary weather protection matters.
In terms of fire safety, Proshield achieves Class B-s1, d0 when applied to suitable substrates, exceeding the minimum standard required for membranes in higher-risk buildings.
An Environmental Product Declaration (EPD) supports responsible procurement and Scope 3 carbon reporting.
What Proshield offers is a way to simplify what can otherwise be a fragmented set of decisions. Membrane, junction tapes, corner details, substrate compatibility, fire classification and environmental data are combined to form a single tested system, with independently verified performance across the conditions that exist on site. www.donlow.co.uk