We're in the process of reducting our house for a central HVAC system.

We have an insulated "cold room" in the basement that had an outbreak of green mold in the past, probably from an old fridge but we're not sure. The room still smells funny after cleaning and humidity always peaks above 60% relative humidity each summer. There are no visible spores but we're pretty sure the problem is still there.

We want to leverage the HVAC system to permanently solve this mold problem by trying to lower the humidity in the room but we're afraid that installing a return duct in the room will spread mold spores into the insulated HVAC ducts (which are impossible to clean) and infect the rest of the house.

Any suggestions?

  • Why not provide a “supply” duct instead of a “return”? – Lee Sam Sep 22 '19 at 15:35
  • @LeeSam I was thinking the same. I'll have to ask my HVAC guy since he was the one to recommend a return in the first place. But even if I go with a supply, there is a risk of it pushing mold from the cold room into the main basement (the two are separated but there is a gap under the door). – Gili Sep 23 '19 at 16:03
  • I would probably add a stand-alone dehumidifier and keep the humidity low enough to keep the mold from becoming active. – Ed Beal Sep 24 '19 at 15:21
  • @EdBeal In theory, I could add a stand-alone dehumidifer, add the duct, then remove the stand-alone dehumidifier. Right? The problem with stand-alone dehumidifers is that they are limited to a single room and need to be emptied manually. I'd prefer to install a whole-house dehumidifier at the furnace and let us take care of all rooms. – Gili Sep 24 '19 at 17:24
  • Well taking air out is one thing but if dehumidified air is not supplied you have a loosing battle. – Ed Beal Sep 25 '19 at 1:13

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