Wall wrap is a key component in modern building envelopes, working primarily to protect the structure from moisture and contribute to its thermal performance. Based on the type described, such as Thermoseal reflective foil wall wraps, its function involves acting as a barrier against moisture and adding insulative value when installed correctly.
Understanding the Mechanism
Wall wrap functions in two main ways:
- Moisture Protection: Many wall wraps, including reflective foil types, are designed to be non-permeable, vapour barrier products. This means they significantly reduce the transmission of moisture into the home, protecting the building structure from potential water damage, rot, and mould growth that can result from moisture infiltration from the outside.
- Thermal Performance: Some wall wraps, specifically those with reflective surfaces, can enhance the wall system's energy efficiency. According to the reference, they are able to contribute a reflective air gap R-Value to the wall system. This thermal benefit is achieved when the reflective surface faces an air cavity, reflecting radiant heat away and improving the overall insulation performance of the wall assembly.
How the Reflective R-Value Works
The reflective property of the wrap doesn't provide direct insulation itself. Instead, it reduces heat transfer by radiation across an air space. For this to be effective, the reflective surface must face an air gap. As the reference states, the reflective air gap R-Value is contributed when positioned adjacent to an inward or outward facing air cavity. Without this air space, the reflective property is largely negated.
Practical Application
- Wall wrap is typically installed on the exterior side of structural framing before the external cladding is applied.
- Proper sealing at joints, windows, and doors is crucial to ensure the wrap acts as an effective moisture and air barrier.
- For reflective wraps, maintaining an air gap (e.g., using furring strips behind the cladding) is essential to harness their full thermal benefit.
Summary of Wall Wrap Functions
| Feature | Benefit | Condition (for Reflective Type) |
|---|---|---|
| Vapour Barrier | Reduces moisture transmission into the home | N/A (inherent property) |
| Non-permeable | Prevents water infiltration | N/A (inherent property) |
| Reflective | Adds reflective air gap R-Value | Must be adjacent to an air cavity |
In essence, wall wraps like the reflective foil types described are dual-purpose materials that fortify the building envelope against moisture while also offering a method to boost thermal resistance through radiant heat control when correctly installed with an air gap.
