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Mold on your Air Conditioner? Causes and Cures.

December 29, 2016 | Blog

Mold on air conditioners is disgusting and hazardous, leaving homeowners wondering where everything went wrong and how to fix it. Here’s everything you need to know about mold in your AC system.

How does it happen?

Mold is common in dark, damp, dirty places, which provide the perfect environment for it to thrive. Unfortunately, AC systems meet this description perfectly. Mold spores naturally traveling in the air attach to damp areas and grow there. AC technicians often find mold on the exterior of air conditioning systems and ducts rather than the interior. Some problem areas for mold are:

  • Supply plenum
  • Air vents
  • Flex ducts
  • Trunk line

How to Eliminate Mold

Mold cannot grow in environments that lack moisture. If you get rid of the moisture, you’ll keep the mold from growing. In HVAC systems, moisture occurs due to the mixing of hot and cold temperatures. It’s the same reason cold beverages sweat and create condensation. The difference between the two situations is that condensation on air conditioners happens for a long time.

When looking for causes and cures for mold growth, you should ask two primary questions:

  1. What is causing water to form?
  2. How do I eliminate the water/moisture?

Stopping Mold in Problem Areas

Supply Plenum

  • Have a professional remeasure the duct sizing to ensure proper airflow through the system.
  • Replace the plenum with a higher insulation R-value.
  • Increase the distance between ducts.

Mold buildup on evaporator coil and supply plenum due to improper duct sizing and insulation value.

Air Vents

  • Replace the grill, ensuring proper size and fit.
  • Properly seal to make sure no attic air is penetrating through the supply box.
  • Make sure that the home does not have outside air filtration (often caused by construction, negative pressure, etc.).

Mold on an improperly installed air vent.

Flex Ducts

  • Have a professional measure the ducts to ensure proper airflow through the system.
  • Keep flex ducts from touching. Ducts that touch create condensation.
  • Install a dehumidifier for the attic air, reducing the opportunity for condensation to form.

Mold on flex ducts that are touching.

Duct Board Trunk Lines

  • Replace the duct board with properly sized ducts.
  • Increase insulation value.
  • Eliminate cold air leakage.

Mold on duct board trunk line.

Mold on air conditioning systems is easily avoidable with proper installation practices and system design. If you have mold on your AC system, contact Mission AC, and let our experts eliminate it fast.

Contact us today to begin your service request.


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