What causes mold to form on air conditioning systems? Simple.
Mold is common in environments that have Dirt, Dampness, and Darkness.
Mold spores naturally traveling in the air attach to damp areas then begin to grow.
I often find mold on the exterior of air conditioning systems more often than the interior. The outside of ducts more often than inside. Supply air grills (see pictures below) as well on the outside of air distribution plenums and trunk lines than internally.
When looking for causes and cures for mold growth on air conditioners and heaters you should ask two primary questions:
What is causing water to form?
How do I eliminate the water/moisture?
Mold cannot grown in environments that lack moisture. Get rid of the moisture and you’ll keep the mold from growing. In an air conditioning and heating system moisture occurs due to the mixing of hot and cold temperatures. Think Condensation. Same reason cold beverages sweat and create condensation is that same reason hvac systems create mold. Now we don’t find mold growing on our beers or soda cans because we don’t give them enough time.
Common causes and cures for mold growth.
COMMON PROBLEM AREAS
Supply Plenum Mold
Supply Air Grills Mold
Flex Ducts Mold
Trunk Line Mold
CURES FOR SUPPLY PLENUM MOLD
Remeasure duct sizing to ensure proper airflow through the system (you’ll need a professional)
replace plenum with higher insulation R value
increase distance between ducts
CURES FOR SUPPLY AIR GRILL MOLD
ensure proper size and fit of grills and ducts
ensure that no attic air is penetrating through the supply box
Replace and properly seal supply box keeping attic air from living space.
Make sure that home does not have outside air filtration (often caused by construction, negative pressure etc.)
CURES FOR MOLD ON FLEX DUCTS
Measure ducts to ensure proper airflow through the system (you’ll need a professional)
Keep flex ducts from touching. Ducts that touch typically create condensation
Install Dehumidifier for attic air (less moisture in the air can reduce opportunity for condensation)
CURES FOR MOLD ON DUCT BOARD TRUNK LINES
Replace duct board with properly sized ducts.
Increase insulation value
eliminate cold air leakage
Mold on air conditioning systems can be avoided. Proper Installation practices and system design will reduce the likelihood of having issues like those shown here.