ASHRAE Handbook of Fundamentals, Chapter 21, Figure 16

ASHRAE Handbook of Fundamentals, Chapter 21, Figure 16

Micro-Venting Wallcoverings

The Len-Tex Corporation strongly recommends, to reduce the risk of fungal growth (mold/mildew), that only micro-vented, permeable wallcovering be used in Humid and Fringe Zone 1 climates. The use of permeable wallcovering is not a guarantee against fungal growth but rather a precautionary tool. Len-Tex offers micro-venting for its wallcoverings and will supply micro-vented wallcovering upon request.

In these above referenced climates the application of non-permeable wallcovering may contribute to fungal growth within the wall cavity. This may occur due to condensation occurring on the inner (cool) wall and being trapped within the wall cavity. (Reference: HUD document 24 CFR Part 3280)

Len-Tex further recommends:

  • The building’s exterior envelope must be weather-tight, and HVAC system must be operating before and during installation.
  • The wall surface to be covered must be completely dry and free of any indications of prior fungal (mold/mildew) growth before installation.
  • The wallcovering supplied by Len-Tex shall be made permeable (approx 15-16 perm rating) by a micro-venting process.

The micro-venting process allows condensation to diffuse (as water vapor) through the inner wall’s gypsum board and applied wallcovering, allowing the HVAC system to perform the dehumidification process. This permeable wallcovering cannot compensate for water intrusion caused by poor building envelope design, faulty construction, building system failure, or improper maintenance practices.

The micro-venting penetrations are only visible when the wallcovering is held up to a light. The penetrations are invisible when the wallcovering is applied to the walls.

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