Your best line of defence against moisture in a high-performance building

Air barriers have quickly become an essential part of modern, high-performance buildings. In New Zealand, the UNI® range from Masons was one of the first complete flexible air barrier systems brought to market. Here we explain how flexible air barriers work, the different systems, and the installation process.

We explain the mechanics that govern the flow of air and water vapour, how flexible air barriers help manage this flow, and why the UNI range is ideal for creating a barrier that not only protects the building and its occupants but also speeds up the construction process.

It used to be said that a house needs to breathe, but in fact, the free exchange of air between indoors and out is not ideal. Drafty buildings are less comfortable and less energy-efficient, and buildings that are not sufficiently sealed will often not meet the more stringent modern building codes and certification requirements. Also, a good degree of airtightness usually assists with better insulation performance and more efficient use of heating systems. The problem, then, is the moisture created naturally as people breathe, cook meals, and launder (and dry) clothes.

Water vapour naturally travels from high- to low-pressure zones, from warm to cold and from wet to dry. Good design will always incorporate passive and active ventilation to shift the majority of moisture loads generated as we live and work in our homes. UNI assists by allowing vapour to diffuse out from moisture-rich interiors to cooler, drier exteriors. This vapour could be described as residual moisture – that which is not shifted by ventilation.

Installed with the appropriate fixings and flashing tape, UNI Flexible Air Barrier forms a substantial barrier to liquid or bulk water whilst effectively blocking moisture-laden air from outside. This keeps the insulation and framing dry, ensuring good performance, and works as a secondary line of defence against moisture over the life of the building.

Available in three grades, UNI, UNI Pro and UNI Plus, the UNI system comprises a three-ply water-resistant synthetic wall underlay, specialised UNI Fasteners and selected 40 Below flashing tape. The UNI range is Codemark certified and has PASS Statements.

UNI’s three-layer sandwich construction includes an outer layer of non-woven polypropylene to keep water out and provide UV protection. The middle layer is a functional-technical film allowing water vapour to pass through while blocking air and water. The rear layer provides additional strength and substance.

Time overruns are probably the biggest contributor to increased project costs. Compared with other building wraps, UNI’s superior strength provides greater weather protection for unclad structures and creates a dry, secure environment where builders can keep working.

Each of UNI’s three grades offers increasing levels of protection. UNI is cost-effective, suitable for most applications and provides 90 days of UV protection. UNI PLUS also provides 90 days UV along with fire retardancy.

UNI PRO offers a massive increase in weather and UV protection – 150 days – and is 22% heavier, especially valuable for builders who expect delays in cladding or are working on long timelines.

All UNI systems can be sealed with either Masons 40 Below Platinum or Flex. Fastenings are UNI Fasteners for use with a hammer or with a UNI Cap Nailer Gun, with galvanised screws and washer fixings for steel frames. There is plenty of support from Masons for first-time users, such as installation videos and instructions, onsite checklists, and personal training with a Mason's rep if required.

For more information, call 0800 522 533 to speak to a Masons team member