Vapor-closed

A vapor-closed construction does not allow water vapor to pass through the building materials. The layers of the wall or roof are sealed to block moisture movement. This approach can be effective when done correctly, but it requires careful design, because any trapped moisture inside the structure cannot escape.

Why it matters:

• Protects the construction from outside humidity.
• Can improve insulation performance if perfectly sealed.
• Risk: if moisture gets trapped inside (from leaks, cooking, or breathing), it may cause condensation, mold, or damage to the building materials.