Recurring growth on greenhouse framing raises two questions: why the surface stays suitable for growth, and whether the material itself needs assessment. A humidity-control response and a material-condition decision address different parts of the problem.
Trace recurring moisture at the affected surface
The University of Minnesota's 2023 Deep Winter Greenhouse guide discusses mold in a northern passive-solar setting. It connects growth with moisture, suitable temperature and organic matter, including locations where condensation accumulates. Preventing recurrence means addressing those conditions rather than only the visible growth. The observation belongs to that greenhouse context, not a universal RH limit. (UMN guide)
Keep appearance separate from wood condition
The USDA Wood Handbook describes surface mold and deeper fungal staining. Their usual strength effects can be slight, but greater absorbency and inconspicuous early decay may accompany discolored wood. Surface appearance therefore cannot certify the condition of a timber member. These are wood findings, not a way to assess metal or glazing. (USDA Chapter 14)
Prepare two distinct review records
For the moisture question, identify the recurring location and when wetness or growth reappears. For the material question, identify the affected component and material, and retain the relevant photographs and observations for the responsible facility specialist.
A dry reading elsewhere in the greenhouse does not describe that particular surface. Likewise, resolving a moisture source does not itself establish the remaining condition of a wooden component. Keeping the two questions separate helps the facility team decide which evidence is still needed.
See greenhouse humidity control for environmental context; unresolved material condition requires its own assessment.
Related project questions
Keep the affected material in view when assessing moisture observations. Compare algae on persistently wet surfaces and Botrytis risk on plant tissue. For the wider project context, return to agricultural humidity control.
