Thread: 'Indoor Only' Ductwork

Does the 'indoor only' mean out of the rain or is it only for interior walls?

I found this in an underfloor crawl space today and it got me thinking....

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Well ... it is no problem in the attic ... which is a different environment than a crawl space, but ... ??? ... it is 'probably' okay in the crawlspace as some "indoor environments" might not be any better, and that would mean one would need to define the environment and not just as "indoors" and "outdoors".

However, typically, "outdoors" means allowed to be exposed to the sun, the rain, the wind, the snow, you name it, all the outdoor weather conditions, and a crawl space offers protection from most of those.

That said ... see those yellow spots on the lower left of your photo?

Yep, those look like tears in the outer covering and that allows moisture in, penetrate through the insulation, and condense on the inner duct core. Reach under the duct and see if the bottom 'feels colder than the sides and top' of the duct, if it does, there is most likely water in there which is making the insulation basically ineffective, meaning a pretty good section of duct will need to be replaced.

If the bottom does not feel colder, it may still have moisture and condensation in it, just not enough to have saturated the insulation YET. Still may need replacing, push the insulation up against the inner duct and try to feel for cold wet insulation, if you can, and it is different than doing the same thing at the side and the top, then it most likely needs to be replaced too. If the bottom feels like the sides and the top (the water would gravitate down and collect on the underside of the inner duct) they the duct may be able to just have the outer covering patched ... but I would defer that to the HVAC contractor to verify moisture presence in the insulation, he can cut it open and patch it back up if okay, but in making that call you will know that the bottom is, or is not, the same as the sides and top, and what that likely means.

thanks JP... fwiw, the picture was taken upside-down so the writing was more readable (I'm guessing you knew that). The crawl was bone dry. The ducts were very light and had no detectable moisture (at least by feel or look).

It's fairly common around here to find ducting full of water. Sometimes on new construction from the ducting being installed early on. I also had a case recently where the carpet cleaners had mistaken the registers on the floor for drains!!! It's quite a surprise as you're lifting a section of ductwork to crawl beneath it and it turns out it's the worlds biggest 'water weenie'. I don't know why but I always want to jab my screw driver into it to see what comes out (I usually resist the temptation to avoid getting soaked).

Originally Posted by Matt Fellman

fwiw, the picture was taken upside-down so the writing was more readable (I'm guessing you knew that).

Matt,

I didn't "know" that it was taken upside down and turned over but I was suspecting that as you were in a crawl space yet the insulation was "down", so I went ... HUH? ... then ... Oh, yeah, probably upside down photo.

Glad to know that I was not crazy thinking that.