Interior Vs Exterior Wrapping Systems

Both interior and exterior passive building wraps play crucial roles in improving a building’s energy efficiency, air quality, and comfort, but they serve different purposes and offer unique benefits based on their placement.

For best results use both together for maximum efficiency and protection in a passive home or energy-efficient design. The exterior wrap provides weatherproofing and wind resistance, while the interior wrap ensures airtightness and regulates moisture from the living space. Together, they create a balanced, high-performance envelope.

Interior Passive Building Wrap

Interior building wraps are typically vapor control membranes or air barriers installed on the warm side of the insulation (inside the building).

Benefits:

  1. Vapor Control and Moisture Management:

    Interior wraps prevent indoor moisture from reaching the insulation and wall structure, reducing the risk of condensation, mould and rot.

    Intelligent vapor membranes adjust permeability depending on the humidity, allowing the building to “breathe” while staying airtight.

  2. Improved Airtightness:

    By sealing air leaks from the inside, they prevent drafts, improving indoor comfort and energy efficiency.

  3. Compatibility with Renovations:

    Easier to retrofit or install during renovations where interior access is simpler than removing exterior cladding.

  4. Energy Savings:

    Reduces heating or cooling demands by keeping conditioned air inside the home.

Exterior Passive Building Wrap

Exterior wraps are typically weather-resistant barriers (WRBs) installed on the outside of the structure, beneath the exterior cladding.

Benefits:

  1. Weather Protection:

    Acts as the first line of defence against rain, wind, and humidity, protecting the building envelope from water intrusion.

  2. Wind-proofing:

    Prevents wind from penetrating the building, reducing heat loss and ensuring thermal performance of the insulation.

  3. Vapor Permeability:

    Allows moisture from inside the wall cavity to escape while blocking external moisture, helping to prevent condensation.

  4. Durability:

    Protects the structural components and insulation during construction, maintaining long-term integrity.

Key Differences

Primary Focus:

  • Interior wraps focus on controlling indoor moisture and air leakage.

  • Exterior wraps focus on weatherproofing and exterior durability.

Moisture Direction:

  • Interior wraps manage moisture from the inside (e.g., from cooking, showering, or breathing).

  • Exterior wraps protect against moisture intrusion from the outside (e.g., rain or humidity).

Installation Location:

  • Interior wraps are applied inside the home, behind plaster.

  • Exterior wraps are placed outside, beneath cladding or brickwork.