Humidity Control Tips


One of the leading causes of mold in warm humid climates is humidity.

Everyone knows that leaks causes mold and that leaks must be repaired as soon as possible to prevent mold growth. However few take elevated humidity seriously, people will live with high humidity for weeks, months, or even years and think nothing of it. Yet it is humidity that causes a thin sometimes almost invisible layer of mold to grow on clothes in our closets, on furniture, and on walls ceilings, and floors.

This surface mold is sometimes referred to as mildew, microscopic analysis will reveal the presence of mostly Aspergillus, Penicillium, and Cladosporium and others. Culturing or DNA analysis reveals much of the powdery white mold to be Penicillium chrysogenum and the black colonies to be Cladosporium. My specialty is dealing with these very specific types of mold problems. The above mold identity observations are based on my own analysis and lab analysis of hundreds of samples.

To prevent such growths from spreading throughout your entire property and potentially covering all your belongings follow these steps:


Most importantly stop humidity at its source. Do not keep windows and doors to the exterior open excessively on warm humid days.


Also in line with source control, ventilate bathroom air to the exterior during and for several minutes after all showers. After doing mold inspections and humidity investigations in South Florida for a decade I can safely say that outdoor air infiltration and showers are the two leading sources of humidity in homes in my area and likely yours as well.


Seal openings in AC closet walls and ceilings. You will not find this one in a book or any other source. I cannot find it anywhere but I can tell you without about that this one can and does cause humidity problems. Openings even a few inches across in an AC closet wall will allow the AC to pull humid air out of the walls. This humidity will then be free to circulate through your AC and through your property. Sure the Will remove some humidity but it can only do so much.


Set your thermostat to auto and not to on. This is another one of those tips that are not well known. Setting your thermostat to on will cause your AC to circulate humid air without drying it, this is obviously a bad thing. Setting it to auto will force the AC to dry and cool your air when it circulates it


In commercial buildings introducing fresh outdoor air into your AC system can be beneficial, and even a building requirement, it dilutes indoor pollutants such as volatile organic compounds and body odor. However in warm humid areas outdoor air being pulled into the AC system will very often overwhelm the AC unit’s ability to dry air and will cause condensation, humidity, and mold inside the system. Some of the buildings and homes with the foulest smelling mold problems are in such a condition because of the introduction of fresh outdoor air. This is truly a case of good intentions resulting in a very negative outcome.

Of course there are other factors to consider such as boiling foods, detached dryer vents, humidistat use, and improperly sized AC units. The above considerations however should cover most situations.  One other thing I did not mention is using a dehumidifier. These devices can be quite effective at removing humidity from your air but they do not solve the problem only mask it. It is almost always possible to cure the problem with a proper understanding of what is causing the problem.

Source: By Daryl Watters for Moldinspectors weblog

The professionals at Aspen Environmental Services recommend professional mold testing and removal to ensure that your home or business is rid of mold. Call us at 978-681-5023 or email us at [email protected]