The first cold night of fall in Western Massachusetts or Northern Connecticut, you turn the heat on and the house smells like a damp basement. It's one of the most common calls we get this time of year, and it's worth paying attention to.
A quick note first: a burning smell for the first hour or so is usually just dust cooking off the furnace after a summer of sitting idle. A musty smell is different. Musty almost always means moisture, and moisture in an air system is where mold and mildew get started.
Where the moisture comes from
All summer, your air conditioner pulls water out of the air. That water collects on the indoor coil and drains through a pan and a line. If the pan doesn't drain fully, or the coil stays damp, mildew can grow there. When the furnace blower starts pushing air across that same area in October, it carries the smell through every vent in the house.
Other common sources:
- Ductwork running through a basement or crawl space, where condensation forms on the metal
- A dirty filter that has held moisture over the summer
- A whole-house humidifier pad that hasn't been changed
- Dust buildup inside the ducts, which holds moisture and gives mildew something to grow on
What you can check yourself
Start with the filter. If it's gray, damp, or you can't remember the last time it was changed, replace it and run the heat for a day. Then take a look at the drain pan under the indoor coil if you can reach it safely, and check any basement ductwork for rust spots or drips. If you have a humidifier on the furnace, swap the pad.
If the smell fades after those steps, you've likely found it.
When it's time to have the ducts looked at
Give us a call if the smell is still there after a new filter, if it's strongest at one or two vents, if you can see dark spots on vent covers or inside the registers, or if someone in the house has allergies or asthma and is having a harder time since the heat came on. Those are signs the problem is inside the duct system itself, and a filter won't reach it.
If we do find growth in the ductwork, that's a different job than routine cleaning. You can read about what mold remediation for HVAC systems actually involves before you decide anything.
Affordable Duct Cleaning serves homes across Western Massachusetts and Northern Connecticut. If your heat smells musty this fall, call us at (413) 359-6570 and we'll help you figure out what's going on.
