Reviewed by the Nampa Mold Experts inspection teamUpdated How we write and check these pages
Short answer: HVAC mold usually starts at a wet spot: the AC coil and drain pan, condensation on ducts running through a hot attic or damp crawlspace, or a swamp cooler's wet pads and reservoir. Ducts in vented crawlspaces can also pull musty crawlspace air into the house. Find the moisture first, then decide what needs cleaning.
Where mold grows in heating and cooling systems
- AC evaporator coil and drain pan: cold, wet surfaces every summer; clogged drains leave standing water
- Duct insulation and lining: condensation on cold supply ducts in humid crawlspaces
- Return-air leaks in the crawlspace or attic that pull in damp, dusty air
- Swamp cooler pads, reservoir and the duct into the house
- Humidifiers attached to furnaces, if not cleaned and maintained
- Dirty filters that collect moisture and dust
Swamp coolers in the Treasure Valley
Evaporative coolers work well in Nampa's dry summers, and some homes still run them. They cool by adding moisture, which means they need regular care:
- Change or clean pads at least once a season, more often in heavy use
- Drain and clean the reservoir; don't let water sit when the cooler is off
- Keep a window or relief vent open while it runs so moist air leaves the house
- Winterize in fall: drain, disconnect the water, and cover or close the duct
- Watch for musty air at the start of the season, a sign of growth over winter
How we inspect an HVAC system
- Visual check of the air handler, coil area, drain pan and condensate line where accessible
- Duct runs in the crawlspace and attic: insulation, condensation, disconnected or crushed sections
- Return-air leaks and where they draw from
- Swamp cooler condition and the duct connection
- Air samples with the system off and running when it helps compare, plus an outdoor control
- Tape lifts or swabs on visible growth inside registers or ducts
Most calls about HVAC Mold Testing in Nampa, ID turn out to involve the crawlspace as much as the equipment. See crawlspace mold.
What fixes HVAC mold
- Fix the drain: clear the condensate line, clean the pan, check the slope
- Seal and insulate ducts in crawlspaces and attics
- Fix the crawlspace if ducts run through a wet one
- Clean the coil and air handler through a qualified HVAC contractor
- Duct cleaning only when there's actual growth or debris; it isn't a cure for a moisture problem
- Replace contaminated duct liner or flex duct rather than trying to clean porous materials
Ask for HVAC Mold Testing Nampa, ID before paying for whole-system duct cleaning. Often the problem is one wet component.
HVAC Mold Testing Nampa, ID: questions
Will duct cleaning get rid of mold?
Only if mold is actually in the ducts and the moisture cause is fixed. EPA notes that duct cleaning hasn't been shown to prevent health problems and isn't needed routinely. Fix the water first.
Why does my house smell musty when the AC turns on?
Usually a wet coil or drain pan, or ducts pulling air from a damp crawlspace. Check the condensate drain and filter first.
Can HVAC Mold Testing in Nampa, ID tell me if my swamp cooler is the problem?
It can raise indoor humidity, especially without a relief window open, and dirty pads or reservoirs can grow mold. Regular cleaning and good airflow prevent most problems. An inspection can tell you whether the cooler is the source.
