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Did I make mistake?

potterdlp's picture

Did I make mistake? (post #213683)

Will try to make it short.  Background: Our crawl space usually dry.  This has been a hot and humid summer in North Carolina 

Today, we noticed the crawl space with moisture..some puddling on floor..from droplets from and on air condition unit metal case..the air carrying tubes too. 

I researched and it seems this can be related to the need for insulation on metal parts, boots, etc., so that when cold conditioned air in tubing meets the warm humid crawl space air condensation won't ensue...I get that.  

My problem::   we recently ( middle of winter 2015)  reinsulated the crawl space joists. I told my husband that to reduce having to do it again...(the old sagged) instead of strapping as contractor did...use landscape fabric. Easy... accessible..breathable..air permeable. .moisture permeable ..just staple it up over insulation after joists were insulated.

HE says (because this is the first time we noticed this) must be because of the one change we made.. ---the landscape fabric. We did my sons the same the same time.  A marathon.  My son's house is conventionally built with wood framing.. Same issue..the boots with water droplets..the air conditioning unit sweating..floor water puddles..  We have an SIP construction.  I say it is the weather, heat and humidity and no insulation around the air the boys did not get around to sealing the floor vapor barrier (winter came quickly) its there but with gaps..and so there is increased moisture from the ground available to condense that was not there before.  The floor barrier completion planned for next month when it is cooler under the houses. 

The son is in a panic thinking the landscape fabric is the culprit and needs to come down.  The husband fears the same.  I do not think thst is the issue. I don't see how it can be.  It is air and moisture permeable and it currently feels dry  ...what do you think???? Again we are in SIP so important that things breathe... I think the house vents through it like it should.. Additionally we have an air exchanger..not pertinent just an FYI.

Did I goof? I have searched everywhere for information, but I only find use of landcape fabric over crawlspace floor..never to secure and hold bat insulation 

thank you for your educated opinions

If by landscape fabric you (post #213683, reply #1 of 6)

If by landscape fabric you mean the felt-like stuff that you can almost see through, then it is about as porous as they come.  It may be contributing slightly to the problem, but is unlikely to be causing it.  And if the ductwork is below the landscape fabric vs being enclosed by it it's hard to see how it could even be contributing.

Recently it's been incredibly hot and humid across much of the US -- some of the worst I've ever seen--, and getting condensation on uninsulated ductwork is not at all unexpected in this situation.

What you really need to do is to insulate the ductwork.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Thank you. I felt that was (post #213683, reply #2 of 6)

Thank you.

I felt that was the case. Yes, it is the black fibrous stuff.  I had no idea there was a netting ( as an option to strapping ) or I would have gotten that. I thought the landscape fabric a great idea...I knew it had to breathe because we have the SIP construction above as I stated.. All ductwork is below the fabric.

Again, thanks for your response. It has eased my mind. 

hold your ground... (post #213683, reply #3 of 6)

Pretty common hereabouts to see scary levels of sweat dripping off crawlspace duct work in brutal summers. I  don't quite get your description of "air conditioning unit" but if there is bare metal under there it will likely condense moisture when it's really hot and humid out. If you have a leaky duct or two it seems to contribute.   Short answer is it seems to me to be very unlikely your landscape fabric is to blame. I actually like the idea if it isn't too costly.  

If said ac unit has a pvc drainline it wouldn't hurt to make sure it is draining. If the vapor barrier joints are contributing much the soil under the barrier should be obviously wet.  


Thank you (post #213683, reply #5 of 6)

Appreciate all input.


to clear confusion...the air conditioning unit outside on a base . A Trane unit.

Under the house is the rest of it -- the part where the ducts branch off. I have not personally seen this mechanical box..I am just relating what my spouse has described.   The furnace is also under there and snakes have been known to take up residence on the furnace and on the joists.., and so I have decided to "see" the crawl space through the eyes of my spouse and son.  I miss ---spoke when I said "air conditioning unit." 

But, from the kind responses....I am comfortable that it is NOT the landscape fabric..and It was not a bad idea. AND, that the boys should have finished the job on the floor barrier regardless of the temps (this I will repeat several times

Potter (post #213683, reply #4 of 6)

6mil or thicker on the soil, lapped at seams and taped.  Sealed at the perimeter.

I'd close the foundation vents spring through fall as the warm moist air coming in will immediately condense on that metal.  No need introducing that into the space.

insulate the ductwork etc.

some use house wrap as a holder of insulation.


how the above jives with sips?  No idea.

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Remodeling Contractor just outside the Glass City.


Air movement (post #213683, reply #6 of 6)

If this is a closed and insulated space it seems to me it should be ventilated by the ductwork in the house, heated or air conditioned.  It should be treated as an indoor space.  Wet ductwork implies it is a warm humid space in the summer.  I think that would cure the problem and wouldn't cost much.