Mold Growth: Why Moisture Is the Real Problem

According to the New York Toxic Mold Task Force study,

“Dampness, excess moisture or water damage in buildings is the major factor in promoting mold growth. That is because spores are always present in the air. Indoors, airborne spores eventually settle on all exposed surfaces, including floors, walls, ceilings and furnishings. If a water source is not present where spores settle, the spores become part of the settled dust that occurs in all buildings. They can remain dormant in settled dust, in some cases for many years, as long as they remain dry. Dormant spores in settled dust will be triggered to germinate and begin growing only when the material where the dust has settled becomes wet.”

This highlights a key truth: mold itself isn’t the starting point — moisture is.Let’s break down how mold develops and what to look out for in your home.

The Mold Lifecycle

Mold spores are invisible to the naked eye, and they’re always floating around us. On their own, they’re harmless. But once they land on a damp surface, they can begin to germinate.

Here’s the typical cycle:

1. Spores land on surfaces indoors.

2. If dry, they stay dormant — sometimes for years.

3. When moisture is introduced, spores awaken and begin to grow.

4. Growth leads to colonies, which then release even more spores into the air, continuing the cycle.

This is why even a small leak or an unnoticed patch of condensation can eventually create a much bigger problem.

Common Sources of Moisture Indoors

Moisture can come from many places, some obvious and some hidden. Common areas where elevated surface moisture is found include:

• Exterior walls, especially corners where temperature differences often create condensation.

• Behind furniture pressed against walls, where airflow is limited.

• Closets adjacent to exterior walls that trap humidity.

• Single-pane or older double-pane windows, particularly metal-framed ones, which are prone to condensation.

• Roof sheathing or attics with poor ventilation.

• Bathroom and kitchen ceilings where steam isn’t vented properly.

Even small amounts of moisture in these areas can provide the right conditions for spores to wake up and grow.

The Role of Humidity

It’s not just leaks or floods — humidity plays a big role in mold growth.There are three key ways to think about humidity indoors:

• Absolute Humidity: The actual amount of water vapor in the air.

• Relative Humidity (RH): The percentage of water vapor in the air compared to how much the air can hold at that temperature. (For example, 60% RH means the air is holding 60% of the moisture it’s capable of holding at that temperature.)

• Specific Humidity: The mass of water vapor in a sample of moist air.

Mold thrives when relative humidity indoors consistently rises above 60%. Keeping RH between 30–50% is recommended for healthy indoor environments.

Why Professional Help Matters

At Utah Mold Pros, we often say: mold is a moisture problem. Simply testing the air won’t solve it. Spores are always present — it’s about finding where they’re growing and why.

If you suspect mold issues in your home, hire a professional. A true investigation goes beyond air sampling. We look for hidden moisture sources, identify active growth, and develop a clear plan for remediation to protect both your home and health.

👉 Have concerns about mold in your home? Schedule a professional inspection with Utah Mold Pros today.