Mold is not always caused by simple roof and plumbing leaks, if the true root cause of an unusual mold problem cannot be properly diagnosed by a certified mold inspection firm familiar with psycrometrics and corrected by a certified remediator  then the mold problem is destined to return after remediation is completed.

Some unusual mold condition that goes undiagnosed are caused by building pressurization problems. Sometimes unusual conditions such as negative building pressurization causes hot humid outdoor air to be pulled into a buildings soffit vents and down into the insides of the walls where the air is allowed to cool. Because cold air is more dense than warm air it holds less humidity and as a result causes the humidity in that air to rise even higher.

Sometimes humidity can become elevated to such a point for example over (60 to 65%RH ) that humidity alone can cause mold growth in the absence of any leaks. This happens every day in musty humid closets where mold grows on clothes and shoes.

If humidity levels get to high the cooled air can no longer hold it's moisture and the moisture is squeezed out of the air.  If you sit a cold glass of ice tea down in a humid environment the glass cools the air touching it and this air becomes dense and squeezes some of it's humidity out this humidity now is water that forms as condensation on the glass.

Below is some information from an inspection that was conducted by our certified mold inspector in West Palm Beach Florida. In it the inspector finds that building pressurization caused a serious mold problem inside walls.

In this report the term house always refers to the Cabana or pool side house. The main house was not inspected thus this inspector does not intend for anyone to utilize these remediation recommendations for the main house. We make no recommendations in regards to mold removal in the main house and have no reason the believe the main house has any unusual mold conditions.

Upon entering the house the inspector immediately detected that the property had a strong mold odor. Next smudges of black mold was observed around nearly 1/2 of the houses electrical outlets and switches, this was mold not soot. In addition similar black mold was observed around many of the baseboard areas.

Moisture meter readings indicated nearly 100% of the wall area tested was moderately moist to very moist when tested.

Humidity readings indicated that the humidity went up and down somewhat, but overall it was typically humidity inside, indoor humidity was higher than the humidity outside on this rainy day.

Indoor humidity was an extremely high 84%RH at 23C indoors at one point, this is extremely high.

Humidity indoors should me maintained between 30%RH and 60%RH anything higher than about 60% or 65% can support mold growth.

Humidity meter being used was a very high end Vaslia humidity meter that was calibrated by the manufacturers recently.

Indoor spore levels were around 2000 spores per cubic meter of air, this is higher than typical.

Spore levels inside the walls were extremely high at around 60,000 pen asp spores per cubic meter of air.

Somewhere between 100 and 300 spores per cubic meter of air is more typical for indoor rooms and also for inner wall air samples.

Spore levels this high in your walls must not be allowed to stay and cannot be simply treated.

Drywall must be all stripped away. No one should sleep in this house.  

So why is all this happening.

It has nothing to do with roof leaks, the roof was sturdy and not weathered, it has nothing to do with ground water or pool leaks despite the houses proximity to the swimming pool.

What is happening is the house is negatively pressurized, this means that the air pressure inside the house is lower than pressure outside the house.

1) Thus the house is like a vacuum and sucks air out of it's walls through the gaps between the base of the wall and the floor, this is behind the baseboards,

2) Air is also being pulled out of the outlet & switch openings in the walls.

3) Now the walls are negatively pressurized so they in turn pull air out of the attic.

4) This causes the attic to become negatively pressurized and pull air in via the screened soffit vents in the roof overhang areas.

The root cause of the negative pressure in the house is the wall mounted AC unit. This is not guess work but was all demonstrated to be occurring with a smoke pen when the AC unit was turned on, when the AC unit was off negative pressurization stopped immediately. When turned back on it started up again.

The AC is creating negative pressure by actively pulling air out of the house through two small holes in the bottom of the AC unit.

In addition this wall mounted AC unit had no visible condensation drain line to drain condensation water to the outside, this is very unusual, where is it's condensation going, it may be blown back into the houses air.

This AC unit was 100% of the cause of the negative pressure that pulled in humidity that in turn resulted in severe mold contamination in the walls.

See photo section of the report and remediation section as well. See remediation section regarding our recommendations.