The Science Behind the ENCLOSURE™ Philosophy
Modern buildings are expected to do far more than simply look good. They must manage moisture, control airflow, improve thermal efficiency, support durability, and meet increasingly demanding compliance requirements, all while protecting the long-term health of the building itself.
The Building Agency developed the ENCLOSURE™ Sheathing System as part of a wider “inside-out” design philosophy. Rather than treating the façade as a standalone surface, the system is engineered to work as a complete external wall assembly, where each layer performs a critical role within the overall building envelope.
At the core of this approach is the relationship between the ENCLOSURE™ Sheathing Board and the ENCLOSURE™ Façade Membrane. Together, these components form a vapour-permeable air seal line, combining the benefits of a rigid air barrier and a water-resistive barrier (WRB). This creates a highly controlled building envelope that manages both air and moisture movement throughout the wall assembly.
Why does this matter? Because uncontrolled air leakage and trapped moisture are two of the greatest causes of long-term building failure.
The ENCLOSURE™ system is designed to stop unwanted air movement and water ingress from entering the structure, while still allowing water vapour to diffuse safely outward. This balance is critical. A building that cannot release internal moisture risks condensation forming within the wall cavity, leading to mould growth, material deterioration, reduced thermal performance, and long-term structural damage.
Importantly, “breathability” in building science does not mean air freely flowing through the wall system. It refers to the controlled movement of molecular water vapour through vapour-permeable materials. Water droplets and water vapour behave very differently; vapour particles are significantly smaller than liquid water droplets, which means the system can be engineered to resist external water penetration while still allowing internal moisture vapour to escape.
Both the ENCLOSURE™ Sheathing Board and ENCLOSURE™ Façade Membrane have been selected and tested for vapour permeability to support this outcome. The result is a wall assembly designed to remain airtight, energy efficient, and weather resistant, while also enabling the building to “dry” correctly over time.
This thinking extends further into overall wall performance and external dew point. In building science, understanding where condensation occurs within a wall assembly is critical. The ENCLOSURE™ system is designed to help move the external dew point outward, reducing the likelihood of condensation forming within internal structural layers. By controlling where moisture can form and how it escapes, the system helps reduce the risk of mould growth and supports the long-term durability of the building envelope.
Ultimately, this is why the ENCLOSURE™ philosophy starts from the framing outward. When performance layers are resolved first, before aesthetic finishes are selected, the result is not simply a façade system, but a higher-performing, more resilient building.
