A new air-conditioning system is supposed to bring relief, not mysterious moisture or mold.
But one homeowner's Reddit post about a wet filter and mold developing above the furnace showed that an installation problem can stay hidden until it affects comfort, air quality, and energy bills.
Here's what to know
A post on the site's r/hvacadvice forum centered on a problem that did not appear until well after a central AC replacement.
"We got a new AC about a year ago, and now the AC furnace filter is damp and top of the furnace is starting to mold," the original poster wrote. "What do y'all think the issue could be? I checked the pan and it's dry, no clog, the coils are clean. Please help!"
With those common issues not turning up anything, the source of the moisture was hard to identify.
Several users focused on condensation in the ductwork as a possible explanation. One advised checking the indoor humidity, temperature of the supply air, and airflow across the coil. "Sounds like your ductwork is condensing," they said. "It could also be an oversized unit or undersized ductwork."
Another possibility raised in the thread involved insulation and the temperature gap between cold equipment and warm air. "Probably lack of insulation in that area causing the super cold air or duct to come in contact with the warm air in the room, causing it to continually condensate," they wrote.
What can be done?
Clearly, a new system is not necessarily an optimized one. Efficient heating and cooling equipment can cut monthly costs, but only if the installation, airflow, and ductwork are all working together properly.
Save $10,000 on solar panels without even sharing your phone number Want to go solar but not sure who to trust? EnergySage has your back with free and transparent quotes from fully vetted providers in your area. To get started, just answer a few questions about your home — no phone number required. Within a day or two, EnergySage will email you the best options for your needs, and their expert advisers can help you compare quotes and pick a winner. Solar panels can save you more than $50k over their 25-year lifespan, and EnergySage can help you save as much as $10k on installation. Which begs the question — isn't that worth an email or two? |
If you notice a damp filter, mold, or sweating near your furnace or air handler, the next step is to have a qualified technician inspect the system. Homeowners may want to ask about duct leaks, insulation, blower speed, airflow, and whether the unit is correctly matched to the home.
And if you're thinking about replacing or upgrading your system, Palmetto can help you understand your HVAC options and slash your energy bills with new, efficient HVAC units and heat pumps. Its Comfort Plan network can help you find efficient heating and cooling solutions for your home and connect you with vetted installers.
The Comfort Plan also includes $0 down options that can lower your heating and cooling costs by 50% and include 12 years of maintenance.
Where can I learn more?
Humidity issues, airflow problems, and drain trouble often show up together. The stories below look at a few ways homeowners have dealt with those headaches, from adjusting settings to staying on top of maintenance and planning upgrades.
• One homeowner found 'dry mode' cut humidity, energy use, and mold.
• On TikTok, a homeowner showed how cleaning AC drains can boost efficiency and prevent clogs.
• Another homeowner turned an AC leak into compost water instead of wasting it.
Moisture around HVAC equipment is usually a warning sign and not something to brush off. Catching it early and making the right maintenance choice or installation fix can help you avoid a large repair bill, mold issue, and wasted energy.
Get TCD's free newsletters for easy tips, smart advice, and a chance to earn $5,000 toward home upgrades. To see more stories like this one, change your Google preferences here.
