Closing a Miami Home for the Summer Without Starting Mold

Leave the air conditioning running at a set point rather than off, and have someone read an indoor humidity meter and check the AC drain line while you are away. EPA advises keeping indoor humidity below 60 percent, and in a Miami-Dade summer the air conditioner is what holds a closed house there.

Already know you need someone out? Call (315) 640-3590.

Why a closed Miami-Dade house gets damp with nothing leaking

A musty smell on the day you come back does not need a burst pipe behind it. EPA's mold course says one job of a building's air conditioning system is to remove moisture from the air before it is distributed through the building, and that if the system is turned off during or shortly after heavy water use, the humidity may rise greatly and moisture or mold problems may develop. In this county the air conditioner is the house's dehumidifier. Switch it off to save on the bill, or lose it to an outage, and nothing else in the house is doing that job.

Miami International's dew point, month by month

The outdoor air explains why. Over a 40 year record at Miami International Airport the mean dew point runs from 60.4F in January to 75.6F in August, with every month from May to October at 69.9F or higher and an annual mean of 68.5F. Dew point is a measure of how much water the air is actually carrying, and air carrying this much does not dry a house by being let in. Opening the windows while you pack trades conditioned air for wetter air. Drying here depends on mechanical dehumidification, which in most homes means the air conditioner running.

The Miami-Dade months you are away are the wet ones

The 1991 to 2020 normals for Miami International give 67.41 inches of rain a year, and 51.64 inches of it, about 77 percent, falls from May through October. June and September are the wettest months, and the station averages 141 days a year with measurable rain. The same normals count 4,659 cooling degree days a year against 104 heating degree days, with no month below 156. The air conditioner and its condensate drain run every month of the year, and a house closed for the summer goes unwatched through the half of the year that brings three quarters of the rain.

Aventura, Key Biscayne and Miami Beach sit partly empty every year

Seasonal homes are not a small corner of this county. The Census Bureau's 2020 to 2024 estimates count 50,471 Miami-Dade housing units vacant for seasonal, recreational or occasional use. In Aventura that is 30.0 percent of all housing units, in Key Biscayne 23.7 percent and in Miami Beach 21.2 percent. In a building where a fifth to nearly a third of the homes may be closed up, the unit above yours may have nobody in it to notice a dripping air handler, which is one more reason to leave someone a key and a written instruction.

Setting up a Miami-Dade home before you lock the door

Four things, most of them cheap. Leave the air conditioning on at a set point rather than off. Put a humidity meter where the person checking the house will see it: EPA says one costs about $10 to $50 at many hardware stores, and advises keeping indoor humidity below 60 percent, ideally between 30 and 50. Keep the air conditioning drip pan clean and the drain line unobstructed and flowing, both of which EPA names. And arrange for someone to walk the house on a schedule, with an instruction to tell you about any reading over 60 percent. If that person may need to deal with an insurance claim, note that the assignment ban in section 627.7152 does not apply to a chapter 709 power of attorney granted to a family member or management company; ask a lawyer or your agent whether one suits you.

What the Irma outage record means for an empty Miami-Dade house

Plan for the air conditioning to stop. A Florida Public Service Commission report on hurricane restoration records a peak of 919,340 electric accounts out in Miami-Dade during Hurricane Irma in September 2017, 80.9 percent of the county's accounts. An outage on that scale removes humidity control from most homes at once, and EPA's window for drying anything wet is 24 to 48 hours. The practical step is naming, in advance, who will open the house after a storm and how it will be dried without counting on power coming back quickly. A flood policy is no help with mold from a cooling failure on its own: the NFIP dwelling form excludes loss from power or cooling failure unless flood damaged that equipment at the property.

Coming back to a musty Miami-Dade home in October

Read the humidity meter first, then look where water gathers: the AC closet and air handler, the drip pan, under the sinks and behind the refrigerator. A small patch you can see, under about 10 square feet, is something EPA says most people can clean themselves once the moisture is dealt with. A smell with nothing visible, growth larger than that, or a stain running toward a neighbor's unit is where a licensed assessor finding the source earns the fee. Tell us in the form how long the home was closed and whether the air conditioning ran, and the reply says which of those you are looking at.