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Have you noticed water stains or peeling paint around the A/C vents located on your ceiling? If you have, your first instinct may be to call a roofer to investigate a roof leak. What you likely have is condensation caused by your A/C System.

Water stains may form on the area where your air vent meets the ceiling’s material (usually drywall or sheetrock) due to a temperature difference in the air and inadequately sealed ductwork. Your A/C System delivers cold air to the entire house via the system’s ductwork, which terminate at air vents often called “registers.” When the cold air within the ductwork mixes with the hot, humid attic air, condensation is created. Therefore, stains around your vent may indicate a duct work problem. If condensation issues are not taken care of in a timely fashion, mold and mildew can start to grow, making a bad problem worse.

It is very important to address a condensation issue immediately upon its discovery. Do not ignore the water stains on your ceiling. Not only is it a problem, but the small stain may quickly spread and lead to increased repair costs and possible spread of mold or fungi. For example, exhaust fans installed in bathrooms often contribute to ceiling water stains. Why? This is because the job of an exhaust fan is to remove moist air and odors from the bathroom and distribute them elsewhere via a duct or simply into the attic. If enough condensation accumulates, it will begin to drain to the bottom of the duct and leak through the ceiling.

Think of it this way: If you take a cold glass of water and place it outside, condensation droplets will form on the outside of the glass. The droplets will then travel down the outside of the glass and create a puddle of droplets around the base of the glass. The type of material the glass was placed upon, such as a wooden table, will become wet from the condensation. This is the same thing that is happening on your ceiling. The materials in your attic are soaking up the condensation and creating a water stain.

Causes of Water Stains

There are several reasons why condensation may build up around your air vents:

  1. Poor Insulation
    Your attic is equivalent to a sauna, with temperatures exceeding 130 degrees during the summer. When the hot air meets the cold air vents, it creates condensation. The water stains on your ceiling could be due to poor insulation. To resolve the issue, a qualified and certified A/C service technician should first inspect your attic. Additional insulation may be the way to create a thermal barrier between the air in the duct work and the attic itself.
  2. Use Insulated Ducts
    Often we find situations where ducts are sweating due to missing insulation or none at all around the exterior of the ductwork. Rodents love to strip ducts of their insulation to make nests. In some cases, older-style flex ducts fall apart in attics due to improper materials used in manufacturing. The excessive attic heat can deteriorate the vapor barrier of the ductwork. Other homes have 40+ year old ductwork that has simply lost its insulating factor, which leads to sweating ducts.
  3. Air Leaks
    Previous studies have shown that 80% of the ductwork in Florida is either undersized or leaking. The cool air passing through your ducts is between 50 and 65 degrees. If there was an air leak, cold air would meet with the hot attic air to create condensation, which typically occurs where there is an attachment point or duct joint. If the joint is not properly sealed, this could create an air leak. Sometimes, simply applying mastic can resolve this issue.
  4. Use the Shortest Run
    When adding exhaust fans in your home, your AC technician should use the shortest route through the attic. The more ductwork the air must travel through, the greater risk for condensation. Your exhaust fans should run straight up from the room in which it is installed and avoid too many connection points.

We at AC Today have certified and qualified Ductwork Specialists who can resolve any and all of the issues listed above. Please call AC Today or stop by our headquarters to have a cup of coffee or iced tea to speak with our Ductwork Specialists!