What is a consequence of installing a vapor retarder facing unconditioned space?

Installing a vapor retarder facing unconditioned space creates a moisture trap because the vapor retarder is designed to prevent moisture from passing through it. When the vapor retarder is positioned incorrectly, such as facing unconditioned spaces like attics or crawl spaces, moisture can accumulate on the warm side of the retarder. This accumulation can lead to various issues, such as mold growth, wood rot, and damage to insulation, as the trapped moisture has nowhere to escape.

In contrast, if the vapor retarder were placed facing the conditioned space, it would effectively minimize the risk of moisture from the living areas entering the building envelope, thus promoting a healthier indoor environment. Understanding the proper placement of vapor retarders is critical in ensuring that buildings effectively manage moisture, especially in climates where humidity levels can fluctuate significantly.