Preventing Mold in Humid Homes

Why do Tampa Bay homes grow mold so easily?

Mold spores are already in every home, indoors and out. They only become a problem when they land on something that stays damp long enough to grow. EPA puts it simply: the key to mold control is moisture control. In a dry climate, a small leak may evaporate before anything grows. In Tampa Bay, the outdoor air is warm and humid for much of the year, so damp surfaces stay damp, and a house that is closed up without cooling can reach mold-friendly humidity with no leak at all.

Most homes in the area sit on concrete slabs, run air conditioning most of the year and take heavy summer rain and the occasional tropical storm. That combination creates a short list of repeat trouble spots: the air handler closet, bathrooms without good exhaust, closets on exterior walls, the slab edge under carpet, attics under leaky roofs and anywhere water came in during a storm. Knowing those places lets you check them on purpose instead of waiting for a musty smell. If you are not sure what early growth looks like, the guide to telling whether a house has mold covers stains, odors and peeling paint.

What indoor humidity should you aim for?

EPA recommends keeping indoor relative humidity below 60 percent, and ideally between 30 and 50 percent. The Florida Department of Health in Sarasota County gives the same practical advice for Florida homes: use air conditioning to keep indoor humidity below 60 percent. A digital hygrometer, sold at hardware stores, is the simplest way to know where you stand. Put one in the main living area and move a second one between the rooms you worry about, such as a back bedroom closet or a bathroom.

How should you use the AC to control moisture?

Air conditioning is the main dehumidifier in most Florida homes. As the evaporator coil cools the air, water condenses on it, drips into a pan and leaves through a condensate line. EPA lists running air conditioners and dehumidifiers among its basic steps for keeping humidity down, and it tells homeowners to keep AC drip pans clean and drain lines flowing. A few habits make a real difference:

• Do not shut the system off in summer to save money while you are away for long stretches. A warm, closed house in July can climb well past 60 percent humidity. Set the thermostat higher rather than turning cooling off, and check the hygrometer when you return.
• Keep the condensate line clear. A clogged line is one of the most common causes of water damage in the air handler closet. Many homeowners flush the line on a schedule; an HVAC technician can show you where the cleanout is.
• Pay attention to how the system runs. A unit that cools the house quickly but leaves it feeling clammy may not be running long enough to pull out moisture. That is a question for an HVAC contractor, not a mold company.
• Change filters and keep supply and return vents open so air moves through every room, including closets on outside walls.

The AC equipment itself can become the problem when water backs up into the cabinet or ducts. That topic gets its own page: see mold in Florida air conditioning systems.

Which rooms need the most attention?

Bathrooms

EPA advises venting bathrooms and other moisture-producing spaces to the outside. Run the exhaust fan during every shower and for a while after, and make sure the fan actually discharges outdoors, not into the attic. Squeegee shower walls, fix dripping fixtures and recaulk failed joints around tubs so water does not reach the wall cavity. Surface mildew on grout and caulk is common and small; it is the kind of job described on the mold and mildew cleanup page.

Kitchen and laundry

Use the range hood when cooking, and vent the clothes dryer outdoors, which EPA also recommends. Check the dryer duct for gaps, and look under the sink and behind the dishwasher and refrigerator for slow leaks a few times a year. A cabinet floor that is swollen or soft is a sign water has been there for a while.

Closets, slab floors and exterior walls

Closets on outside walls get little airflow and can stay several degrees cooler than the room, which makes them a favorite spot for mildew on shoes, bags and stored clothing. Leave closet doors open some of the time and avoid packing items tight against the wall. EPA cautions against installing carpet where there is a constant moisture problem, including on concrete floors that leak or have frequent condensation. On a slab that sweats, hard flooring is easier to keep dry than wall-to-wall carpet.

Attics and roofs

Roof leaks after storms are a leading cause of hidden growth on roof decking and ceiling drywall. After any strong storm, look in the attic for wet insulation or dark staining on the underside of the roof. Growth on decking is covered on the attic mold removal page.

What about seasonal homes and houses left empty?

Seasonal ownership is common along the Gulf coast. On Longboat Key, condominiums are a major housing type and a large share of housing units are seasonal, recreational or occasional-use, according to 2020 Census figures. In Englewood, a large share of units are counted as vacant for seasonal use. A home that sits closed for the summer is exactly the setting where humidity drifts upward without anyone noticing. If you leave for months:

• Leave the AC running at a moderate setting rather than off, so it keeps pulling moisture from the air.
• Consider a dehumidifier that drains to a sink or floor drain, not into a bucket that fills in a day.
• Have the condensate line flushed before you leave, and leave interior doors open.
• Arrange for someone to check the hygrometer and look for water after storms.
• Use a smart thermostat or humidity sensor if you want readings while you are away.

How fast do you need to dry water after a leak?

EPA says water-damaged areas and items should be dried within 24 to 48 hours to prevent mold growth. Fix the source first, then dry. Pull wet rugs up, open cabinet doors, run fans and a dehumidifier, and keep the AC going. Wet drywall that stays wet beyond that window, or wet insulation inside a wall, often needs a closer look; the page on mold inside walls explains what that involves. After a storm surge or rising water, the rules are stricter, and the Tampa Bay flood guide walks through them.

What should you not do?

• Do not paint or caulk over mold. EPA says to clean and dry the surface first; paint applied over growth tends to peel.
• Do not rely on cleaning alone. EPA is clear that if you clean up mold but do not fix the water problem, the mold will most likely come back.
• Do not keep moldy porous items you cannot clean. EPA notes that porous materials such as ceiling tiles and carpet may have to be thrown away if they become moldy.
• Do not run the HVAC if you suspect it is contaminated. EPA warns it could spread mold through the building.

When is prevention no longer enough?

EPA says that if the moldy area is smaller than about 10 square feet, roughly a 3-foot by 3-foot patch, most homeowners can handle the cleanup themselves. Larger areas, growth after significant water damage, mold inside walls or ducts, and repeated growth in the same place call for outside help. Mold exposure can irritate the eyes, skin, nose, throat and lungs, and EPA advises that people with asthma or weakened immune systems stay away from moldy areas. Anyone with health concerns should talk to a health professional.

In Florida, the work is usually split between two businesses. Under section 468.8419 of the Florida Statutes, a mold 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. So expect a mold inspection in Tampa to come from one company and the removal from another. You can check either person's license status with DBPR's online licensee search, and the guide to vetting a Florida mold company lists the questions to ask.

For budgeting, Angi reports that mold remediation in Tampa typically runs $1,347 to $3,778, and a bathroom job typically $525 to $1,075. Those are reported ranges, not quotes; the size of the area, what has to be removed and access drive the final price. The Tampa mold remediation page explains what a full job includes. Renters have different options than owners, covered in the guide to mold in a Tampa Bay rental.