Mould in your heat pump: signs, risks, and what to do
A dark, humid, rarely-inspected space with a steady supply of dust. Heat pump coils might as well be designed for mould.
How mould ends up in a heat pump
The coil and drain pan stay damp through the cooling season. Dust and organic matter land on them continuously. Temperature is mild. That's three of the four things mould needs. The fourth is time, and time happens whether you want it to or not.
Halifax's humidity and proximity to the ocean accelerate the process. We see visible mould growth on heat pumps as young as 18 months old in homes near the harbour.
Signs you probably have mould
Black or dark-grey streaks on the louvers. Musty smell on startup. Visible dust that feels slightly wet to the touch. Allergic symptoms that flare up when the system is running. Increased humidity in the room despite the heat pump running.
If any of those apply, don't wait. Mould spores become airborne every time the fan kicks on.
What removes it
Surface-cleaning the visible mould does nothing. It's growing inside the coil. The only way to reach it is a full disassembly, coil-specific cleaner that kills and breaks down the biofilm, a thorough rinse, and an antimicrobial treatment to prevent regrowth.
We do this routinely, every day. What surprises homeowners most is how much comes out. The runoff from an uncleaned coil looks like strong tea.
Common questions
- Is the mould in my heat pump 'black mould'?
- Usually no. Most heat pump mould is common environmental mould (cladosporium, penicillium) rather than the toxic stachybotrys. All of it should still be removed. Spores are spores.
- Will cleaning fix it permanently?
- It resets the clock. With annual deep cleans, the antimicrobial holds up well and mould stays away. Miss a year and it'll come back.
- Can I install a UV light to stop mould?
- UV can help in some ducted systems but isn't effective in most ductless mini-splits because of geometry. Cleaning is the reliable answer.
Ready for a deep clean?
Put this into practice in your home.
Book online in two minutes. Free estimates, no obligation, evening and weekend slots available.