# Insulation condensation



## k.hinton (Aug 18, 2011)

Recently I have installed 2" of ridgid insulation to my basement walls. Tuck taped and spray foamed every seam. My question is. At the floor it appears I have some water forming. A few table spoons. I know it's not alot but it is something and I'm not sure why it is forming. My grading around the house is great. Now I am only getting three spots like this in a 1300 sq ft badement. If u have any thoughts let me know.


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## TarheelTerp (Jan 6, 2009)

k.hinton said:


> At the floor it appears I have some water forming. A few table spoons.
> Now I am only getting three spots
> 
> If u have any thoughts let me know.


Archeology 101:
Carefully remove the insulation at one of those spots (or all 3)...
see if you can identify the route the water is traveling and it's source.

Based on your findings... do what you can.
hth


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## Windows on Wash (Aug 30, 2011)

If you are sure that the water is not coming through the basement wall, than the issue is interior air making it to the cold concrete and condensing.

You will need to re-check all your seams and make sure there are no gaps.

It likely was not an issue previously because you had air circulating against the concrete and in doing so kept it warm enough to avoid dew point.


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## TarheelTerp (Jan 6, 2009)

Windows on Wash said:


> *If you are sure* that the water is not coming through the basement wall, than the issue is interior air making it to the cold concrete and condensing.


If it was occurring generally as in more than just the three spots... I'd tend to agree.
But the OP offers no reason to be sure...



> It likely was not an (observed) issue previously because you had air circulating against the concrete and in doing so kept it warm enough to avoid dew point.


Maybe.
OP: how long have you been in the house?


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## Windows on Wash (Aug 30, 2011)

TarheelTerp said:


> If it was occurring generally as in more than just the three spots... I'd tend to agree.
> But the OP offers no reason to be sure...
> 
> 
> ...


If you have a seam that is open in one of the foam boards, moisture and condensation can be very localized in this case. 

I agree that the OP needs to post up more details.


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## Gary in WA (Mar 11, 2009)

I've read in a few places that moisture is condensing on the cold concrete walls but is dispersed by the moving air currents immediately upon forming........ does that sound right? From Building science and fine homebuilding.

Gary


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## Windows on Wash (Aug 30, 2011)

GBR in WA said:


> I've read in a few places that moisture is condensing on the cold concrete walls but is dispersed by the moving air currents immediately upon forming........ does that sound right? From Building science and fine homebuilding.
> 
> Gary


+1

The rapid movement of air (warm air) strips the condensation off. With a rigid foam board and a nearly tight air barrier, this will not happen. If enough air is getting through, it will generate the problem without being able to self correct.


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## dsmith10 (Jan 4, 2012)

I agree with the statement:

"If you are sure that the water is not coming through the basement wall, than the issue is interior air making it to the cold concrete and condensing."

If you are absolutely sure that that it is not coming from the basement walls then I would recheck your seams - from what you have said it seems like the likely explanation. 

--------------------------------
Condensation Control


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## k.hinton (Aug 18, 2011)

Appreciate all the great information.. I know that no water is coming through my foundation. Not only is my grading ok but I also have applied Sani Tred to the walls a added protection. Before I insulated I made it a must too and look over the basement for leaks before I applied the board... When I did apply the board I literally have spray foamed every seam there is down there and also applied tuct tape to every seam.. Now along the floor I havnt applied anything.. Is that where I have went wrong. Also I havnt done vapor barrier but I was under the impression that it wasn't required with foam board. I heat my house with a wood stove which is in the basement so there is lots of hot air and air movement at that.. So with this issue if I used platon flooring should I be concerned with the little amount of water or really go to town and consider doing vapor barrier


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## Windows on Wash (Aug 30, 2011)

k.hinton said:


> Appreciate all the great information.. I know that no water is coming through my foundation. Not only is my grading ok but I also have applied Sani Tred to the walls a added protection. Before I insulated I made it a must too and look over the basement for leaks before I applied the board... When I did apply the board I literally have spray foamed every seam there is down there and also applied tuct tape to every seam.. Now along the floor I havnt applied anything.. Is that where I have went wrong. Also I havnt done vapor barrier but I was under the impression that it wasn't required with foam board. I heat my house with a wood stove which is in the basement so there is lots of hot air and air movement at that.. So with this issue if I used platon flooring should I be concerned with the little amount of water or really go to town and consider doing vapor barrier


Vapor barrier necessity depends on the type of foam board used.

What did you use?

If you used EPS or unfaced XPS/Iso, you still can get enough vapor diffusion in some cases.


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## k.hinton (Aug 18, 2011)

I did use eps style for foam boarding.. Now could I use a foil instead of vapor barrier to reflect heat back into the interior or just use regular vapor barrier. Once again appreciate everyone's advice.


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## TarheelTerp (Jan 6, 2009)

k.hinton said:


> I heat my house with a wood stove which is in the basement...


With this new information... I'll suggest you deal with the modest symptom the same way that my grandmother did in her root cellar 75 years ago: one of those dry rid products.

Grandma had a cotton bag of it hung from a nail.
It worked fine.

hth


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## rightit (Mar 5, 2011)

Here is more information which I coincidentally came across earlier today:

http://www.buildingscience.com/docu...-insulation?topic=doctypes/information-sheets


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## Gary in WA (Mar 11, 2009)

*Where are you located?*

The thickness of foamboard needs to be correct for your location (dew point of cavity). 

Adding a plastic vapor barrier or foil-faced polyiso could work... depends on location and thickness of board.

Gary


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## k.hinton (Aug 18, 2011)

I live in Ontario Canada in a city on lake Ontario. The foam is 2" thick


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## Windows on Wash (Aug 30, 2011)

k.hinton said:


> I live in Ontario Canada in a city on lake Ontario. The foam is 2" thick


Not enough thickness when using EPS for up there.

You need a vapor barrier in this application. A non-perforated radiant barrier will do the trick as well as adding a layer of rigid foil faced iso or poly skrimmed XPS.

2" of EPS is not enough in this case (roughly R-7).


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