by Patti Dees

Common problems with HVAC systems tend to result in moist environments. That moisture breeds mold, mildew and bacteria that can damage property and occupant health. Fortunately, good maintenance practices help identify current problems and prevent growth in the future.

Identifying Mold in Commercial HVAC Structures

Excess moisture and mold growth are among the most common issues encountered in HVAC systems. Since HVAC design touches every part of a building, from the building envelope to interior piping, this creates many opportunities for water to wreak havoc. Some of the signs that should trigger investigation and repair are musty odors, water stains and puddles and an uptick in occupant respiratory illnesses.


Wet materials and molds themselves can produce odors. In some cases, this may be the first indication of a problem. Look for the source of the odor to determine if there is a microbe-loving environment in the making.

Stains and puddles

Leaks from piping runs and valves for heating or cooling water, as well as excessive condensation buildup, may leave visible indicators. Dry and repair these issues as soon as noticed to head off the mold.


Molds are sneaky. Their spores are not limited to their immediate environment. Some may even be carried through the HVAC system to other parts of the building. Mold spores can cause respiratory issues such as asthma as well as headaches and even neurological problems. Occupant health complaints should be taken seriously as a possible sign of HVAC issues creating undesired moisture in the building.

2Causes of Mold

Treating the mold without addressing the conditions that encourage its growth only temporarily resolves the problem. The key is to limit factors such as food and water that allow mold to gain a foothold in the first place.

Removing dust and debris around HVAC equipment is good for reducing the organic material that mold feeds on. However, the real impact comes from limiting access to water. HVAC systems have many ways to create moist environments.


Outdoor HVAC equipment requires openings in the building envelope. This allows moisture to enter the building, making it difficult to control the humidity within. High humidity also contributes to condensation along ducts and piping, especially if they are poorly insulated. As mold likes humid and wet locations, this issue creates double the problems.


Not all condensation is bad. HVAC systems incorporate condensate lines and drain pans because some condensation is expected. Even this source can create unwanted moisture if lines become clogged or drain pans overflow.


Piping runs for refrigerant and heating are not infallible. Leaks happen, usually at joints and valves. Because pipes tend to be placed out of view, small leaks may be missed. As time passes without repair, conditions can encourage mold growth.

How to Prevent Mold

There are many ways to prevent mold in a building, rather than just remediating it after staff or occupants find it. Minimizing the chance for HVAC-related mold growth begins at installation. Properly sized units, thoughtful design elements and a focus on maintaining effective seals and insulation for the building envelope and ductwork are the first steps in preventing mold.

Once installed, however, vigilance through preventive maintenance and monitoring are necessary. Preventative maintenance limits the chance for water to contribute to mold growth. By identifying potential leaks and damaged insulation early, maintenance tasks help keep areas dry. Investing in preventive maintenance tends to cost much less than mold remediation and repairs from long-standing leaks.

In addition to proactive maintenance plans, other technologies can improve mold defense. Facility managers can install automated systems to help them monitor and manage HVAC equipment. UV-C lights can be used to keep equipment in hard-to-reach locations clean of organic material. Antimicrobial agents can be added to water and refrigerant to protect lines and coils.

Goodbye, Mold

There are options for both new constructions and existing facilities in the fight against mold. As the primary defense against mold, HVAC preventive maintenance plans protect property by removing sources of water. Occupants can breathe easier — sometimes literally — when managers prioritize prevention over remediation. Therma can assist managers and owners with their HVAC system design and maintenance as they say goodbye to mold.

Patti draws on her background as a chemical engineer to share information with readers on technology, manufacturing and construction.


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