It’s a core goal in building a home that moisture should be kept out as much as possible, and for good reason: it rots wood, rusts metal, and fosters mold. But solid walls and roofing can’t keep out one source of moisture you should be aware of: your ventilation system.
Condensation occurs when hot air, laden with water and very humid, comes into contact with a cold surface. Cold air can’t hold as much moisture as warm air, so the extra condenses onto the metal surfaces. It’s the exact same process that causes your cold drink glass to be covered with water droplets on a hot summer day. As the very job of your HVAC ducts is to shuttle around hot and cold air, it’s understandable that they can suffer from the same problem.
Water droplets from ventilation can be spotted almost immediately or may not make themselves until a serious problem has occurred. If you’re lucky, you’ll see droplets coming out of ceiling vents or notice small, unexplained water drops on walls and ceilings. If you’re not, you won’t know you have a problem until you discover mold or structural elements are sagging, buckling, or even collapsing due to rot.
Well-constructed ducts will have special ductwork insulation to keep temperatures within a safe range and avoid condensation. You should have your HVAC contractor check on your duct condensation if you suspect a problem, or add it to your annual inspection. Even a small crack insulation can cause condensation, and no matter what, proper insulation will improve the efficiency of your HVAC system.
If your insulation is in good shape and you’re still having condensation problems, the issue is likely with the climate of your home. Very humid areas have ductwork moisture as a common foe, especially if you like the temperature in your home somewhat high. While your A/C will have a dehumidifying effect on its own, adding a dedicated dehumidifier in the worst rooms in your home can make a big difference. You should also make sure your AC’s coils aren’t frozen over, as that can damage its ability to dehumidify. Finally, if you went all-out and bought a system took powerful for your home, it may simply not run long enough to properly dehumidify.
Letting moisture sit can turn a minor annoyance into a huge, costly problem quickly. If you ever suspect moisture, be sure to contact your HVAC contractor as soon as possible.