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Humidity Testing And Mold Problems In Hot Humid Climates

In hot humid climates, such as are encountered in tropical and sub tropical regions around the world proper humidity testing and control can be crucial to properly understanding and solving a mold problem.

In fact many coastal homes in Florida and the South East experience mold problems in the absence of any leaks. Many homeowners and even mold inspectors fail to properly understand the connection between common building defects that cause humidity and the buildings mold problems. Sometimes large oceanfront mansions have constant or reoccurring mold problems that go on for many years.

According to all the reliable text and experts including but not limited to Bioaerosols Assessment and Control, Institute of Inspection Cleaning Restoration Certification S500, and S520, EPA Guidelines and many more mold can become a problem when humidity goes above 60% to 65% RH. Pleases note that 60% RH is not optimal but may be just barely adequate humidity levels to support a small amount of the most drought tolerant molds. The higher the humidity, the more mold growth will occur.

Humidity levels that are too low also cause problems. Humidity levels below 30% cause dry lips, dry throats, and other increased health complaints such as drying mucous membranes and an increased risk of catching colds. Low humidity can also increase static electricity that can in return damage computer data. To be on the safe side, keep your humidity between 30% and 60% RH.

A few species of xerotorlant pen asp mold are commonly found indoors. xerotorlant is just a fancy was of saying drought tolerant. I like to call these molds humidity molds. These molds by definition do not require as much moisture as other molds, but they still require moisture. They can grow in the absence of leaks by simply living on the humidity content (ERH) that they absorb from growth surfaces in humid environments. Simply, here is how it works. Humidity in the air absorbs into the growth surface such as drywall, wood or clothes, the humidity levels in these substrates known as equilibrium relative humidity goes up in direct proportion to the humidity in the air. This causes the available moisture content (wA) in the substrate to go up. Thus, the humidity in the air eventually ends up being absorbed into the clothes in your closet and into the drywall in your home and then by the mold.

Humidity in and of itself causing mold growth is not the only concern from elevated humidity. It will also prevent proper drying of wet surfaces when leaks occur. If you own an ocean front property in Florida, Louisiana, or the Carolinas, and have high indoor humidity and a leak occurs then you are courting trouble. Especially, if you are out of town when all this occurs because the leak will not dry up before mold sets in.

This inspector (DW) often finds two types of xerotorlant molds, again these molds do not require much water but only what they get from humidity. One specific type of humidity loving xerotorlant pen / asp mold grows on dark black clothes and black leather shoes and purses. Why does this mold like black clothes? It grows on all clothes but it is almost always completely invisible on other clothes because the mold forms small white circles about 1/8 inch across that only shows up on black clothes. This mold loves clothes, luggage, leather, wicker items and sometimes walls.

It starts out first in your closet because drying air circulation is typically lower in closets.

If you find your mold inspector inspecting you shoes and clothes don't freak out, he is just doing his job.

One important fact is that this mold when it first starts may be almost completely invisible to the untrained eye, yet it has been demonstrated to cause seriously elevated spore levels in the air, furthermore you may be wearing this mold on your clothes and the mild odors associated with it everyday and suffering from allergenic reactions as a result long before you find out what is happening.

The other most common xerotorlant humidity mold that I know of that grows in humid indoor environments but does not require leaks is a slow growing golden tan form of pen /asp. Specifically it is a type of Aspergillus that loves to grow on painted wood, painted drywall, and on books, it also forms colonies about 1/8 inch across and like the white mold above is not found around leaks. If you find your mold inspector looking at your books he is likely not reading but may be inspecting for these mold colonies. If you are familiar with faxing or yellowing of old books and documents you already have an idea of what this mold looks like. This mold and the oxidation of paper that results in faxing are likely sometimes confused with each other.

There are many ways that humidity or moisture can be measured in the air. Inspectors utilize two methods on a regular basis during comprehensive mold testing and humidity testing investigations.

Relative Humidity

Relative Humidity compares how much water vapor is present in the air to how much water vapor would be in the air if the air were saturated with water vapor.

Mixing Ratio

Mixing Ratio also measures the amount of water vapor in the air. But, mixing ratio measures the mass of water vapor for a given mass of dry air. We typically express it as grains of moisture per pound of dry air. That is grains not grams.

RH vs. MIXING RATIO

There is a strange phenomenon to take into consideration when measuring the amount of water in the air using relative humidity - the colder a parcel of air is, the more humid it becomes, even if you do not add water to it. And the warmer a parcel of air is, the less humid it becomes, even if you do not remove water from it.

When measuring the amount of moisture in air using mixing ration, temperature will not change the inspectors readings, thus the inspector should use mixing ratio measurements in hot or cold spaces so temperature changes do not affect the readings.

Example I:

Inside an attic in a tropical region the temperature may be 100° F and the humidity may be 50% RH. This is an acceptable humidity level if all you consider is relative humidity. Many Florida mold testing investigators may not think anything of this; however, with the use of, a good quality humidity meter or a cheaper meter and a psychometric chart, we see that this hot 100° F air at 50%RH actually contains about 145 grains of moisture per pound of air. That is a some what high amount of moisture to have in your attic, if it is raining outside it may not be unusual but if this amount of moisture is always in your attic you may have a problem; in fact, if a cold front moved in and the temperature dropped to 88° F in that attic at night, the relative humidity would be 70%RH. These are wonderful conditions for many molds and bacteria, and they will accept your invitation to take up residence. If a few nights later the temperature drops to 78° F in the evening without the addition of any new moisture from outside, the humidity would go up to 100% in your attic, at this point, condensation would form. Metal may rust, and mold would grow on the outer surfaces of your attics ductwork if conditions are not improved.

Example II:

Inside a hot attic that receives humid breezes from the ocean via the attics soffit vents the attic temperature may be 100° F and the humidity may be 50% RH. This is an acceptable humidity level if all you consider is relative humidity. This hot 100° F air at 50%RH actually contains about 145 grains of moisture per pound of air. That is a some what high amount of moisture to have in your attic, in may not cause a problem in your attic but if you live near the breezy ocean in South East Asia, Hawaii, Florida or the South Eastern United States it may be like this in your attic much of the summer.

If the ocean breezes entering your attic via the soffit vents pressurizes your attic and blows this humid attic air into your hallow wall voids and into the house via a loose fitting attic access or via top hat light openings in the ceiling then the air will encounter indoor temperatures of around 78° F.

Without the addition of any new moisture from outside, the humidity in the attic air that escapes into your house would go up to 100%, at this point condensation would form and cause mold growth on cooler ceilings where the air is escaping from the attic, or at the top areas of closets where circulations is poor. This condition confuses many of our clients and even other mold inspectors and eludes attempts at correcting the problem sometimes for years or decades.

So now what?

If you have humidity related mold do not just keep wiping it off your shoes, one day you will find that is has spread to your clothes, furniture, walls, books, and artwork. Do not ignore it and do not hire a cheap mold inspector to take a few quick air samples you will just be wasting your money and time.

If you want your problem properly assessed you are going to need a comprehensive building investigation that is designed to put all the pieces together, it must be conducted by an engineer, licensed mold assessor, industrial hygienist, or certified indoor environmentalist, who has some knowledge of building construction, HVAC systems, complex humidity issues, and mold ecology. The person you hire is going to have to find out where the humidity is coming from then they are going to have to advise you on some ways to keep it from getting in.

In attention they are going to need to assess your HVAC system to assure that it is properly drying your air.

About the Author

Daryl Watters is a certified mold inspector, certified home inspector, and certified indoor environmentalist providing testing services and building inspections since 1993. For more information visit
http://www.floridamoldinspectors.us

http://www.florida-mold-inspection.com

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