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laura_mae

Crawlspace condensation issues, flex duct dripping

11 years ago
last modified: 11 years ago

Location - Middle TN.

Current summer weather - highs in mid to upper 90s, humidity peaks at 90% and drops to 60% outside. Dewpoint hovering around 72. At times 75-76. Does drop on occassion below 68. Zone 7 - Winters are generally mild with occassional lows between 5-10 degrees, but generally 20 plus degrees in dec - jan

Gas pack installed outdoors, approx 4 years old. Inside is comfortable in summer and winter and utility bills are lower than average conpared to friend's in the area.

House was built in 2000 on a tall crawlspace - 5ft in most areas with rear wall partial concrete block with wood framed wall above as lot is sloping and first floor at rear is 7 feet above grade. Due to the sloping front to back lot there are a few drainage channels that cut front to back in the cs and I havent seen any standing water. House is 3 sided brick, with vinyl on back side.

I purchased the house in spring 2014 and noticed odors coming from the crawl but not having had a cs prior i didnt notice the insulation wrong or the missing black plastic in places and only corrected the issue by using the mastic tape to seal gaps at register boots from inside the house. The problem appeared "fixed" as no more musty smells coming in the finished living space and there still isnt.

Three days ago, in prepping to install new flooring, my moisture meter alerted high moisture on the plywood subfloor in multiple areas which I recognized as the flex duct path in the cs. A trip to the cs found sweating insulated flex duct that was dripping, batt insulation drenched as it was installed up against flex duct as well as very wet moldy subfloor around register boots due to batt insulation packed up against.

Several flex ducts are pulling away from boots (cheap tape was used) and some of the factory insulation got wet. I found several duct leaks at places where they join boots.

I immediately removed all wet insulation from the cs ceiling area.

Further examination revealed black plastic isnt covering the entire dirt/rock floor. Large gaps between seems and appears never fully covered the width of the cs.

There are lots of vents but as you see from weather info its just pulling hot humid air in to then condense and add to the problem.

So, what is my most affordable option to address this? Funds are somewhat limited right now (ie I dont have 5-10k to fix this - closer to 1-2k max).

I have spent hours reading and the choices are overwelming Im fairly good at diy and the cs has electricity and is fairly tall.

It would seem at a min I need to remove the current plastic ground cover thats in poor shape and get 10mil plastic (from where?) and cover the earth as well as concrete block walls. And remove the rest of the fiberglass insulation. But, how hard of a diy project is the plastic portion? Any tips or tricks to make install easier? And what plastic to buy?

Should I also try to fill all holes, gaps, block vents and add a dehumidifier?

Or is there a better aoproach given the issues and budget?

And what else do I need to do? I need to address the flex duct at boot issue. Any advice on the best way to fix that?

Comments (7)

  • 11 years ago

    Properly installed ducts will not sweat regardless of how humid surrounding air is. One red flag in your discription is "cheap tape was used". Flex duct is best secured with Zip-ties. The linner is normally taped to boot then insulation and outside cover pulled over linner and secured with Zip-tie. If you reconnect ducts to boots,buy the special tensioning tool to pull Zip-ties tight. It sounds like conditioned air is finding it's way out of the spirial wire linner then flowing against outside cover. There might be holes in linner or linner might be disconnected from boots. Another possibility is that duct is simply not well enough insulated.

  • 11 years ago

    It appears to be the flex duct that comes with insulation wrap already attached. How do I know if it has the right amount of insulation? Ever inch of flex is sweating profusely. Apparantly its a common enough site in the SE that people think its "normal".

    On the zip ties - I do not think those were used but can confirm. To make sure I understand, I would use those to essentially cinch the flex tight?

  • 11 years ago
    last modified: 11 years ago

  • 11 years ago

    Unfortunately, in our neck of the woods, sweating flexduct is not uncommon. You need to do all of the things you have proposed - plastic sheeting over the entire crawlspace floor, taped at the seams. Humidity will still wick up through the block foundation wall so you need a dehumidifier down there also. A 70 pint Home Depot Special should be sufficient. If you don't have any drainage options, get one with a built-in condensate pump (or install a separate one). Crawlspace sealing if rife with scammers - you are better off doing it yourself, if you can.

  • 11 years ago

    Glad to know Im on the right track. I spent 7 hours today in the cs. Removed the ripped apart black plastic, any trash etc from the original owner, fitted the new plastic in - ran out of time today to get walls done and tape it all up.

    My cs has trenches that appear to be lined with concrete and rest has thick layer of gravel. But, when removing last piece of old plastic I found some standing water in a trench. Should there be a drain somewhere? I havent found one near there. Found this black pipe on opposite end , overall the grade does slope towards it, but the way the trenches are cut I dont think it would ever make it there

  • 11 years ago

    Sorry for sideway pics - not sure why they did that! But you can kinda see there is one trench that runs the width of house down center, then 3 trenches run from it to the exterior rear wall, but at that wall there is not a trench that runs from one corner of the rear wall to the other corner which is the lowest point. Is that typical?

  • 11 years ago