How can I get rid of the mildew smell in my home after cleaning and inspecting the HVAC return?
Asked by Yannik Gautier 
7 months ago
Last Updated: May 8, 2024
Hey, can you lend a hand? We’ve been working hard to get rid of that musty smell by tearing out walls and cleaning the wood and drywall. But despite our efforts, the smell lingers. I just checked out the main HVAC return and noticed a couple of things. First, there’s this broom-looking thing. Second, the middle of the return seems to be missing some metal and instead has what looks like rock wool or insulation. Any idea what’s going on here?
The brush is from a duct cleaning company that had a malfunction with their equipment and lost the cleaning head. The soft lining inside ducts helps reduce noise from the airflow and might also provide insulation. I’m not an expert, so I’m not sure how you’re supposed to clean that material.
The broom seems like it was used to clean, but the handle broke off, right? It’s interesting that there’s only one insulated duck section. I had an insulated duct replaced in 1990. Can you tell which picture shows the missing metal?
The majority of this duct, which is the primary vent for all the others, is made of straight metal. This section seems to have insulation. Could this be the source of the mildew smell? How should we proceed with replacing or removing this?
By I’m not entirely sure if that’s where the smell is coming from; my guess would be probably not. As Mark mentioned, the sound is likely due to the expansion and contraction of the ductwork when the heat turns on and off. The rest of the duct appears to be clean. Have you noticed any dampness in the basement? Does the smell become stronger in the basement? (assuming you have one) Do you only notice the smell when the furnace and blower are running? Where in the house do you detect the smell the most?
Found himself near this large duct. The living room is on one side, and the guest room is on the other, and the smell was strongest there. We removed walls because the living room had old 70’s wood paneling under some strange textured paint. It was beneficial because it needed a thorough cleaning behind it. The window insulation in the guest room was discolored, so we replaced it with spray foam. All the drywall and insulation in these rooms have been replaced, and they are still intact. This particular section of the house sits on a slab. On the other side, we have a very shallow crawl space that we completely cleaned and encapsulated about 5 months ago when we purchased the house.
Standard duct lining is typically used to minimize sound, like with rockwool insulation.
How can we get to it for replacement? Do we need to cut the metal first and then weld it back together?
Did you get your air handler cleaned recently? If the condensate drain is slow or clogged, it can lead to algae and mildew in the unit.
I believe so. Is that included in the annual HVAC maintenance? We recently had that taken care of. I’ll give them a call tomorrow to confirm.
By My HVAC system has a plastic pipe for condensation to drain when the A/C is on. Sometimes it gets clogged. There should be a plastic screw (if yours is plastic) on the top (outside the unit) that you can unscrew, run some water down and check if it’s draining properly. Mine drains into a floor drain.
Is it raining outside?
By Nope, my unit is located in the basement with the pipe leading to a drain in the floor. I remember in my previous unit there was dirty water accumulating on a metal tray below the interior unit’s condenser coil. The water is supposed to drain through the plastic pipe, but it got blocked so I had to clean it. I have a very thin metal snake that I use to clear the pipe as far as it can reach.
By it’s typically included in the annual maintenance.
There’s duct liner in there – it’s insulation. Looks like someone dropped a duct cleaning brush.
Hey, I’m pretty new at this. Can anyone tell me why only a small part of the vent in my living room is insulated, even though it spans the whole room and is about 5 feet out of 20 feet?
By explained that if the duct runs through an unconditioned area, it’s lined or wrapped. I personally line mine even in conditioned areas to minimize noise.
Try finding a handle that can extend and has a hook or something similar to pull out the brush attachment. Then try attaching it to something to help remove the dust and other debris inside.
My husband mentioned trying with two golf clubs 🤦♀️
I believe using a clamper might work better.
By I don’t mind if it stays in there, but I like to ensure the lines are clear
By, please make sure to take pictures if he cleans the golf clubs 🤣
Spouse:
I’ve experienced this before, had the a coil cleaned, and it solved the smell issue.
Thank you! It seems like I’ll have to contact the HVAC company again.
By mentioned using a foam spray to clean the ducts, you just apply it and let it sit.
Oh I see. Thanks!
The previous owner paid for duct cleaning and ended up getting more than what he expected.
You’d be a great fit for duct cleaning and HVAC maintenance. It’ll improve your health and your unit’s efficiency. When running our HVAC systems during renovations, it can strain them. I usually change filters weekly until the painting phase, then again once everything is back in place.
The insulation is likely trapping various debris. However, it’s unclear if it’s advisable to attempt removal.
In my personal experience, HVAC cleaning is not effective in removing that. I have tried it before. The dirt is stubbornly stuck, not just surface dust.