Mold Testing

What Is Mold And How Does It Get In Your Home?

Ok, I’m going to assume if you landed on this page you already know what mold is, so I won’t get too technical and scientific on you.

So here it is in plain English:

It is a type of fungus that usually grows indoors in humid wet environments.

There are over 365,000 types of mold species, however, only a handful of them are normally found indoors and harmful.

Most mold spores are non-toxic and may not affect humans unless that have a certain type of allergy to that particular mold species.

Mold can be indoors and outdoors, but you don’t care about it being outside.

You want to know how it got in your home, correct?

Mold In Your Home

mold entering the home

Yes, you likely have some mold spores in your home.

They could have been brought in when you opened your doors or windows, carried it on your clothes, brought in by pets, or maybe even on some of your food.

But look:

Those are perfectly normal situations.

What we are worried about is mold growing on building material throughout your home such as on walls, interior doors, in cabinets etc.

When mold actively colonizes and starts growing is when you really can start having problems whether it be related to health issues or damaged building material.

How Does Mold Start Growing Indoors

You need three things for mold to grow:

  • Moisture
  • Relative Humidity Above 60%
  • A food source such as drywall or wood

One other thing which fits this category would be time.

Some mold can generally start growing within 24-48 hours, however, there are certain types of mold spores that can take much longer to grow. Those are usually the more dangerous types of mold aka “black mold”.

Once you have those three present, any mold spores floating around in the air will attach itself to the water damaged building material and start growing.

Here’s an example for you:

A leak has suddenly occurred under your kitchen sink.

It is going behind the sink base so you cannot actually see anything. It’s only dripping a little bit of water at a time so there are no puddles anywhere.

But one day you decide you want to renovate your kitchen…

And you find this:

mold behind kitchen

But why did mold grow here?


You had a leak which provided the moisture.

The area behind the sink does not get any kind of air conditioning and is almost certainly over 60% relative humidity.

And then you have the food source which is organic building material.

BINGO! Perfect conditions for mold to grow.

Mold will only grow on porous surfaces. While it will not actively grow on non-porous surfaces, it will land on there and hang out there.

The HVAC System

Remember the three things that you need in order for mold to grow (moisture, humidity, food source)?

Once misconception is that in order for these three things to be present, there must be a leak.

While some sort of water leak can certainly be the cause of mold, there is another issue which is overlooked…

…The air conditioning system (HVAC)

The HVAC system (air conditioning) keeps the home cool. Older air conditioning systems may have something called a humidistat which is where you can control the humidity in the home.

Newer systems do not need humidistats because modern air conditioning systems are built to dehumidify through the HVAC unit itself.

Here’s where the problem comes in:

When the air conditioning unit is not properly dehumidifying but still properly cooling.

Let me explain…

When an HVAC unit is not dehumidifying but still blowing cold air, the mixture of the cold and humid air causes condensation.

Once you have condensation that is landing on a food source, and the environment is already humid, mold can start to grow on porous contents and building material throughout the home.

Another issue is when the thermostat has been left in the “On” position for an extended period of time. This can cause excess cold air into the home which can lead to condensation and eventually mold.


mold in ducts

Another issue with the HVAC system is mold within the duct work. This is a little bit of a misunderstood concept. Many people think that duct cleaning is a scam, but it may be necessary.


I am not saying that there aren’t companies out there that are unethically telling you that you need to clean your ducts, but in certain cases, dirty duct work can affect the overall air quality within the home.

Mold does not generally grow on the duct work itself.

What happens is dirt and dust build up in the duct work and mold will grow on that opposed to the actual ductwork.

It’s not just mold that can affect the air quality. All sorts of particles and debris that gets removed when the ducts are cleaned.

What is the Difference Between Mold And Mildew

mold vs mildew

Almost every time I am called to a home where the owner suspects mold due to odors, they always refer to it as a “mildewy” type smell.

Here’s the issue with that:

Mildew grows on living plants and not building material.

That stale kind of smell that is referred to as “Mildew” is generally either mold or a home that has not had sufficient air exchange.

98 out of 100 times when a homeowner reports having mildew in their home, they are incorrect.

Mildew is also the title that people give mold to minimize the damage and make it sound like no big deal. Often times during a pre-purchase inspection I hear a realtor refer to mold as mildew and say something along the lines of:

“It’s just mildew, it’s not a big deal…”

When in fact it is mold.

Sometimes it is just surface mold and can be wiped off with a biodegradable solution.

My Point is this:

Don’t be fooled when somebody says a stain is just “Mildew” because in all likelihood it’s not.

If you hear those words come out of a Mold Inspector’s mouth and there are no living plants present, it’s possible, you didn’t pick a good inspector.