The floodwater is gone. The power is back on. It’s Houston, so it’s hot, and your first instinct is to flip on the AC.
Stop. Here’s what you need to know first.
Running your HVAC system after a flood — before it’s been assessed — can do several things, all of them bad:
Most Houston homes have the air handler in the attic (relatively safe from flooding), in a utility closet (varies), or in a ground-floor mechanical room or garage (highest risk). The air handler is the indoor unit — it contains the evaporator coil, the blower motor, the condensate pan, and the electrical controls.
If floodwater got into the mechanical room where the air handler sits, assume the unit was exposed. Even if the unit itself appears dry, floodwater wicks into insulation around refrigerant lines and into the filter housing. Have it inspected by an HVAC technician before running it.
The outdoor condenser — the unit outside your house — is designed to be weather-resistant. Submersion in floodwater is a different matter. If the condenser was submerged, the compressor and capacitor may be damaged. Running a flooded compressor can destroy it entirely.
Four things need to be confirmed before you run your HVAC after a flood:
This is the less obvious issue. Even if your HVAC system itself is perfectly fine, running it while active mold remediation is underway — or while wet building materials are still drying — can undermine the remediation.
Professional mold remediation uses negative air pressure containment: HEPA-filtered air scrubbers create a pressure differential that draws air into the work zone rather than out of it, preventing spores disturbed during work from traveling to the rest of the house. Your HVAC system pushes and pulls air throughout the house continuously. Running it while containment is active works against the pressure differential the remediation crew has established.
Most remediation contractors will ask you to shut off the HVAC system for the duration of the containment phase. If they don’t mention it, ask.
If floodwater or significant mold contamination reached the duct system, duct cleaning alone is not sufficient under IICRC S520 standards. Ducts that have been contaminated with Category 3 water or significant mold growth may require duct replacement — cleaning can remove visible debris but doesn’t ensure pathogen elimination in contaminated ductwork.
For ducts that were not directly exposed to floodwater but were in service during a flood event, professional cleaning and antimicrobial treatment is appropriate. Have this done before extended system operation.
In Houston’s summer heat, going without AC during restoration is genuinely uncomfortable and can slow drying by raising indoor humidity if managed poorly. Discuss the timeline with your restoration contractor — most drying phases complete within three to five days, and temporary spot cooling options exist for occupied portions of the home.
Your insurance’s Additional Living Expenses coverage may apply if heat makes the home uninhabitable during restoration.
Don’t run the HVAC after a flood without confirming the air handler and condenser weren’t submerged, the ducts weren’t exposed to contaminated water, and the filter is replaced. If remediation is active, the system should be off. The short-term heat discomfort is far less costly than distributing contaminated air through every room in your house.
If you need HVAC assessment as part of flood recovery or you’re not sure whether your system was exposed, call 247 Restoration Specialists. We coordinate with HVAC contractors and can assess the full picture — what’s wet, what’s contaminated, and what needs to happen in what order.
If the ducts run through a space that was flooded — crawl space, first floor, garage — assume they were exposed and have them inspected. Signs of duct contamination include visible debris or sediment in supply registers, musty odor when the system runs after the flood event, and visible water staining on duct insulation. An HVAC technician or restoration company can do a direct inspection with proper equipment.
Damage from an internal flood — a burst pipe that damaged the air handler — is typically covered. Damage from external flooding (bayou overflow, storm surge) is flood damage and requires separate flood insurance through NFIP or a private flood policy. The standard homeowners HO-3 policy explicitly excludes this. If you’re in a FEMA flood zone in Harris County and had a flood insurance policy, the HVAC equipment may be covered under the building coverage portion.
Until the system has been inspected and cleared by an HVAC technician, and until active remediation containment is removed. In most Houston flood recovery situations, that’s 3 to 7 days from the flood event. The exact timeline depends on the extent of water intrusion and the remediation scope.
