Airtightness that works on site, not just on paper
Airtightness targets are tightening. Air testing is stricter, and the margin for error on site is reducing.
For contractors delivering modular and high-rise projects, the challenge is rarely about understanding the principle of airtightness. It is about achieving consistent results in real build conditions, with multiple trades, tight programmes and constant sequencing pressure.
Air leakage often occurs at the detail. Junctions. Openings. Fixing points. Areas where membranes are cut, taped or mechanically fastened. Each penetration is a potential weak spot.
At the same time, sealing a structure too rigidly without allowing vapour movement can create condensation risk inside modern wall systems. Airtightness cannot come at the expense of moisture management.
This is why the market is shifting towards self-adhered airtight membranes that reduce on-site variables while maintaining vapour permeability.
Proshield ® from Don & Low has been developed with that purpose in mind
Independently certified by KIWA, Proshield ® is a self-adhered, vapourpermeable airtight membrane suitable for walls and floors. By bonding directly to fibre cement, calcium silicate, OSB, timber, concrete and steel, it removes the need for mechanical fixings or primers. Fewer fixings mean fewer potential leakage paths.
With air leakage below 0.01 m ³/ m ²· h at 50Pa, it supports demanding airtightness targets. An Sd value of 0.098m allows moisture vapour to escape, helping reduce condensation risk within the structure.
Fire performance is also critical, particularly as the requirement increases within high-rise and modular developments. When adhered to suitable substrates and tested to BS EN 13501-1, Proshield ® achieves Class B-s1, d0, exceeding the minimum regulatory requirement for membranes.
On-site, accuracy matters. A printed alignment grid assists installation, while compatible tapes and preformed corners support airtight detailing around windows, doors and junctions. These are often the points that determine whether a building passes its air test without time consuming remediation.
As compliance pressure increases and programmes tighten, contractors are prioritising solutions that reduce installation risk and improve repeatability. Airtightness must be reliable in practice, not just on paper.
Proshield ® represents a practical approach to achieving that balance.
For more information or technical guidance: 0808 169 4444 membranes @ donlow. co. uk www. donlow. co. uk
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