AC Mold in Florida Homes

Why does AC equipment grow mold in Florida?

An air conditioner is a moisture machine. As warm, humid air passes over the cold evaporator coil, water condenses on the coil, drips into a drain pan and leaves the house through a condensate line. In Tampa Bay, where the system runs most of the year and summer air is heavy with moisture, that is a lot of water moving through a small, dark cabinet. As long as it drains, the system is helping keep the house dry. When it does not drain, the same equipment becomes one of the wettest places in the home.

The usual failures are predictable. Algae and sludge build up in the condensate line until it clogs. The pan fills and overflows onto the platform, the closet floor or, for attic units, the ceiling below. Rust holes open in older pans. Ducts sweat where cold supply air runs through a hot attic. Duct insulation or duct board gets wet and stays wet. EPA tells homeowners to keep AC drip pans clean and drain lines flowing, and its duct-cleaning guidance adds that substantial standing water or debris in a drain pan needs immediate attention.

Where does mold show up in an AC system?

Spotting on a register is not always growth inside the duct. Often it is surface growth on the grille caused by condensation in the room, and it points back to humidity rather than the ductwork. The guide to keeping humidity down in a Florida house covers that side of the problem.

What should you do first?

1. Stop running the system if you suspect contamination. EPA says not to run the HVAC system if you know or suspect it is contaminated with mold, because it could spread mold throughout the building. In a Tampa summer this is hard, so get help quickly rather than leaving it off for days.
2. Deal with standing water. Clear the pan and the condensate line, or call an HVAC contractor to do it. A float switch that shuts the unit off when the pan fills is worth asking about.
3. Dry what got wet. EPA says to dry water-damaged areas within 24 to 48 hours. Pull up a wet closet carpet, open the closet and run fans.
4. Look at the materials. Hard surfaces such as a metal pan or grille can be cleaned. EPA notes that porous materials may have to be thrown away if they become moldy, and wet drywall behind the unit may need to be cut out. The page on mold behind drywall in Tampa explains how that is handled.

Can you clean AC mold yourself?

Some of it. Flushing the condensate line, cleaning a grille and wiping a small spot on the closet wall are routine tasks. EPA says that if the moldy area is less than about 10 square feet, most homeowners can handle the cleanup. Wear gloves and eye protection and keep the area ventilated.

Growth inside the air handler cabinet, on the coil or blower, or inside ducts is a different job. Opening the system, removing wet insulation and cleaning without spreading debris through the house is work for professionals, and it usually needs an HVAC contractor as well as a mold remediation company. Mold exposure can irritate the eyes, skin, nose, throat and lungs; EPA advises that people with asthma or weakened immune systems stay away from moldy areas, and anyone with health concerns should talk to a health professional. The HVAC and duct mold service in Tampa page describes what that work involves.

What does EPA say about cleaning ducts?

EPA's guidance on duct cleaning is more cautious than many sales pitches. The key points:

• Sheet metal ducts with substantial visible mold growth are a reason to consider cleaning.
• Wet or moldy duct insulation, including the insulation inside flex duct and duct board, cannot be cleaned effectively and should be removed and replaced.
• Biocides: EPA notes that no biocides are registered for use inside internally insulated ducts. Ask to see the label of any product a company proposes to spray.
• Sealants should never be used to cover wet duct liner or actively growing mold.
• Health promises: duct cleaning has never been shown to prevent health problems, so be wary of an offer built on health claims.

Ask any provider to show you the mold it says is there, and make sure the plan addresses the cause, whether that is a drain problem, sweating ducts or high humidity. Cleaning ducts without fixing the moisture means paying for the same job again.

Who does the work in Florida?

An AC mold job often involves three roles. An HVAC contractor repairs the drain, pan, coil or ductwork. A mold remediation company removes the growth and damaged materials. A mold assessor evaluates the problem before the work and can check the result afterward. Florida law keeps the last two separate: under section 468.8419 of the Florida Statutes, an assessor may not remediate a structure it assessed within the past 12 months, and a remediator may not assess a structure it remediated within the past 12 months. Expect the mold assessment in Tampa and the removal to come from different companies, and expect any clearance check after remediation to come from an assessor, not the remediator.

Testing is not always needed. EPA says that when mold is visible, sampling is usually unnecessary, and there are no federal limits for mold spores. Surface sampling can be useful to confirm an area has been cleaned. The guide on when mold testing is worth paying for covers the details. You can check the license status of an assessor or remediator with DBPR's online licensee search, and the guide to checking a Florida mold company lists questions to ask.

What does AC mold remediation cost in Tampa?

Angi reports a typical range of $3,225 to $10,750 for mold remediation in HVAC systems in Tampa, well above its typical range of $1,347 to $3,778 for remediation overall. Angi puts mold inspection at $300 to $1,075, and HomeAdvisor reports testing at $327 to $903 in Tampa. These are reported ranges, not quotes. The main cost drivers are:

• How far growth has spread from the air handler into the ductwork
• How much duct insulation, flex duct or duct board has to be replaced
• Whether drywall in the closet or the ceiling below has to be removed
• Access: a tight attic platform costs more to work on than a hall closet
• HVAC repairs to the pan, coil or drain, which are usually billed separately

For a fuller breakdown by location in the house, see Tampa mold remediation prices. Homeowners in nearby communities can find local help through the Brandon AC and duct mold and St. Petersburg duct mold pages, and businesses with larger systems can start with commercial mold remediation.

How do you keep AC mold from coming back?

• Keep the condensate line flowing and the drain pan clean, as EPA recommends, and have the system serviced on a regular schedule.
• Keep indoor humidity below 60 percent; a hygrometer near the thermostat makes it easy to check.
• Do not shut the system off for long periods in summer, especially in a closed-up seasonal home.
• Look in the air handler closet every month or two for water, rust or a musty smell, and check the attic unit after heavy storms.
• Replace any duct insulation that gets wet instead of hoping it dries.