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Air Conditioning Condensation Problems

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As per the norm, I am basing today’s topic on a very common occurrence here in the sunshine state… duct work that is forming condensation and supply vents sweating. I see duct work that is forming moisture on almost a daily basis. So first, let’s look at the whys when it comes to wet ducts.

In a properly functioning air conditioner the air leaving the unit is going to be around 20 degrees colder than whatever the set point on the thermostat is. If the thermostat is set at 73 then the air leaving our unit is going to be right around 53 degrees. Next, please stop and consider that on a hot summer day it is not uncommon for an attic to hit 150 degrees. I don’t want to bore you with a long science lesson so keeping it simple think about taking an ice cold can of soda out of the refrigerator and setting it on the patio table — what happens? The can will start to sweat, right? That is the exact same thing that is happening when your ducts are leaking cold air out into the hot attic space. Make sense?

This is where we need to look at how bad the condensation is to determine the extent of the needed repairs. If the duct system is extremely old (over 40 years) it is highly probable that the only remedy to stop the condensation is going to be replacement of the duct system. As a warning, duct system replacement is a major project, usually involving cutting ceilings, a few days without air conditioning and a major expense depending on the size of the home.

Next up, in a duct system that is between 5 and 35 years old, we can take a hard look at resealing the duct work to bring it back to as close to new as possible. The process is called Aeroseal™ and the best analogy I can use is Aeroseal is Fix-a-Flat for a duct system. We temporarily make the duct system a closed loop, an ultra fine mist is injected into the ducts and when the mist finds a hole it seals it. Aeroseal has a 10-year warranty and does a great job stopping condensation, reducing dust and helping to deliver all the air you are paying to cool into your home.

If the house and the duct work are under five years old and you are getting condensation it is likely due to the builder taking a short cut when the home was built. Look up at one of your supply vents, what is holding that vent up is screws that go into a can in the attic. The can is lowered into a hole that was cut in the drywall and mounted from the attic. If the hole that was cut for the can is even 1/16” bigger than the can, there is an air gap to the attic.  This will allow heat transfer from the attic causing the vent to sweat. Builders typically don’t worry about sealing that gap as when the grille is installed it hides the gap and of course, out of sight out of mind. This issue is a pretty minor fix that can even be a DIY project on a Saturday afternoon. All you need is a screwdriver and a caulking gun. Take down each grille and caulk that gap between the can and drywall, put the grille back you may have just solved your own problem, just be careful on that ladder.

Other things such as leaving windows and doors open can cause condensation and I have seen some complex issues in condos where condensation in one unit was being caused by what was going on in another unit. The bottom line is if you are having a condensation issue with the duct system in your home get us out to have a look. It is something we have seen thousands of times and we have specialized tools to dial in the exact root cause.

Alright everyone thanks for stopping by and shout out to people who don’t know the opposite of in.  House Whisperer out!!  


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