Hurricane Milton (2024) • Greater Tampa Bay
Wind-Driven Rain & Systemic Humidity Stacking
Hurricane Milton impacted Greater Tampa Bay with extreme wind velocities, causing widespread roof damage and wind-driven rain intrusion. Coupled with extended power grid failures, this created ideal conditions for systemic humidity stacking and HVAC contamination.
Wind-Driven Rain and Attic Insulation
Milton's wind profile forced rain under soffits, through ridge vents, and around compromised roofing materials. This water directly saturated attic insulation (fiberglass and blown-in cellulose). Saturated insulation compresses, losing its R-value, and traps moisture against the ceiling drywall.
This sustained moisture leads to Cladosporium and Aspergillus growth on the attic side of the ceiling. Because attics in Florida reach extreme temperatures, the moisture is driven downward into the living space, a process known as humidity stacking.
HVAC Grid Failure and Spore Dispersal
The prolonged power outages following Milton eliminated the primary mechanism for indoor moisture control: the HVAC system. Indoor relative humidity (RH) quickly stabilized at ambient outdoor levels (80%+). At RH levels above 60%, airborne mold spores settle on dust and organic materials and begin to colonize.
When power was restored, HVAC systems pulled these settled spores into the return plenums. The condensation inside the air handler provides the necessary moisture, turning the HVAC system into a mold amplification and distribution network.
Clinical Case Scenario: Tampa, FL
"Wood-frame home, Tampa. Minor roof shingle loss during Milton led to localized attic wetting. Power was out for 9 days. Occupants reported strong musty odors when the AC was turned back on. Testing confirmed a systemic Cladosporium colonization of the fiberglass ductwork. Remediation required full attic insulation removal and complete duct replacement."