system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is it that houses in various stages of construction can get drenched in rain, yet not develop a mold problem after completed?

I've seen stacks of lumber, insulation and other building materials get drenched at residential construction sites, yet it doesn't appear to worry the builder. How does that moisture, once closed up inside walls, not turn into a mold factory?
gpt
Getting wet isnt a problem for most stages of a homes construction. Staying wet is the problem. Lumber getting rained on doesn't really increase the moisture content in the wood that much. Its normally somewhat damp to begin with. The only problem with damp walls would be when its time to install sheet rock. Sheetrock is always covered because it cant get wet.