Funky Smell in Ductwork

Replies to This Discussion

Permalink Reply by Pat Dundon on November 2, 2012 at 12:52pm

have you tried to run a blower door there?  it really has little to do with what I think is happening, but if this is the problem, it will amplify it quickly so you will know. 

did the remodelor somehow cut the plumbing vent line?  did he leave it dead ended in the attic or somewhere in a wall?  do you have a malfunctioning vent termination?  I don't know what they call them, but occasionally plumbers put a termination on a vent line that is supposed to only let air in, but never let air out of the plumbing vent.  they are commonly burried inside a wall. 

running heat may change pressures enough to make something that works at 0 stink at +/-1. 

I have accidentally found broken plumbing vents in 2 houses, and several where the vent terminated inside the attic while doing a blower door test. 

not the most pleasent experience. 

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Permalink Reply by Dick Meyer on November 4, 2012 at 2:30pm

It's possible that a leaky return duct could be sucking in gasses from a terminated vent line.  BTW they're called, air admittance valves (generically) among other things and yes, they can malfunction.  If your code permits them, they are restricted to one per living unit, should be installed horizontally, and must be readily accessible (not buried in a wall) if installed correctly, among other things.  I would be more inclined to insure that all ducts are sealed and then trace the path of the vent pipe from the point that it penetrates the roof down through each of the plumbing fixture groups before beginning the search for a malfunctioning AAV.  A borescope might be helpful.

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Permalink Reply by Patrick Michaelyan on November 4, 2012 at 3:18pm

Thanks Dick, that is helpful.

Reading your reply reminded me that I forgot to mention an important fact...the ducts are all flex duct, but there may have been some pan-joisting for the returns.

I will still try to trace the vent pipe and see what this may tell me.

Patrick

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Permalink Reply by Dick Meyer on November 4, 2012 at 4:03pm

I hope not.  Pan-joisted return ducts are the leakiest of the leakiest ducts.  A very bad idea.  I think the first priority here is to find the source of the obnoxious and dangerous fumes and the second is to figure out how to seal the return.  Hopefully the return is not too long and you can convince the owner to replace it with a conventional duct with all seams sealed with mastic.  Short of that, you could try house wrap tape, but to me, that's a distant second choice.

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Permalink Reply by Patrick Michaelyan on November 4, 2012 at 4:20pm

I hear you Dick.

I was not happy to see the pan-joisted return ducts, and I made this known to the homeowner. I think this homeowner is a smart cat, and will do what is required to resolve this situation, especially if I tell him that we may be facing a dangerous issue.

As for the sealing of the pan-joisted return ducts, I am a firm believer in the power of duct mastic. Ideally one would replace such ducts (as you mention), but I take what I can get.

Thanks Dick!

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Permalink Reply by Dick Meyer on November 5, 2012 at 4:48am

Patrick, two thoughts:

1. I mistakenly said that AAV's should be installed horizontally.  It's just the opposite, should be vertically.

2.  If the owner elects to try to seal the existing pan-joists, perhaps a one-part foam would be the best answer as I'm sure that neither mastic nor tape are tested or approved for metal to wood or drywall contact.

Good luck!  Would be interested to see you come back and tell us the outcome of the story.

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Permalink Reply by Patrick Michaelyan on November 6, 2012 at 12:28pm

Thank your sir.

I'll make sure to follow up.

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Permalink Reply by Curt Kinder on November 5, 2012 at 7:00am

Open sewer vent during blower door test...been there, done that...yuk! In my case, plumbing fixtures were not yet installed so I taped over the openings so I could keep down my lunch.

Agree that wall cavity joists are an energy disaster, also a fire hazard. If nothing else, perform a ductblaster test to highlight the leakage almost certainly occurring.

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Permalink Reply by Tal segal on November 8, 2012 at 6:34am

I had funky smell in my ductwork too,

my HVAC tech fixed my ductwork but the smell didnt go away, i bought 2 unit of dual lamp uv germicidal and the moldy smell start go away! its really work.

i reseach prices arroud for the dual unit, and i find the best one on ebay, here is the link

http://www.ebay.com/itm/Air-Purifier-UV-LIGHT-ultraviolet-AC-hvac-d...

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Permalink Reply by Kevin DeBord on November 16, 2012 at 8:44am

Obviously all of the prior recommendations could be correct however there is another possibility. In the HVAC industry it's typically referred to as "Dirty Sock Syndrome". It occurs in heat pumps and shows up in the heating cycle. The smell is the result of microbial growth on the indoor coil. Typical treatment options involve cleaning the coil. Some of the most effective methods are a three step process that involves cleaning the coil, then treating it with an anti-microbial agent and a coil coating that inhibits growth on the coil. In many cases this must be repeated every year or two. A quality UV light properly installed and maintained can kill the organisms and prevent them from returning. Of course this is more effective if the coil is cleaned and treated first.

There are several chemical companies that have effective products for this issue; NuCalgon and Atlanta Chemical are two of them.

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Permalink Reply by Patrick Michaelyan on November 17, 2012 at 4:31am

Thanks a lot Kevin.

I will soon take all of these recommendations to the HOs, and then work with my HVAC partners to hopefully resolve this issue.

I'll follow-up if and when we resolve this issue.

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Permalink Reply by Colin Choney on November 20, 2012 at 4:21pm

Hi Patrick, just curious if you ever determined what was causing the smell and what the solution was to correct the issue

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