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Discussion Starter #1 (Edited)
Advise needed !! Frost inside exterior walls in basement

hello everyone,I am new to this forum and had posted this question in the general topics section,but in hindsight I think I should have put it here.
I have copied and pasted it here, any comments or thoughts are appreciated

We are finishing our basement at the moment. we removed the vapor barrier and insulation to install some wiring and a switch box. I was surprised to find a fair amount of frost on the inside of the walls.

The outside temperature is currently -24 C or 12 below 0 F so I would expect to see some frost on the walls. Do you think the frost in the photo is excessive or normal? the pinkish stuff in the picture is insulation, the frost is white

 

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Discussion Starter #3 (Edited)
Your structure has a bad air leak causing the frost and possibly a water leak looking at the left portion of the pic.
Thank you for the comment I appreciate your thoughts and would appreciate some more of them,so here is some more info for you

The House is new, we had it inspected and could find no leaks. The insulation stops are all ok, and there is plenty of insulation in the attic and there is no water dam on the roof or water leaking through the roof. The house is wrapped in tyvek so we can't figure how we can have an air leak. There are no water lines in the wall anywhere near where this moisture is in the framing. The dark stains on the floor joist look like water stains but are not.

These new homes do not have chimneys, they pipe the furnace and water tank off gasses thru the walls and right outside. Like most new homes they are close together and the "steam" from my neighbours home does at times blow against my home, but we don't think that's the issue.

Any more of your thoughts or comments are appreciated.

thank you
 

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Was that frost uncovered when you pulled out the insulation--or did it grow after you exposed the cold wall sheeting?
 

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Discussion Starter #5
Was that frost uncovered when you pulled out the insulation--or did it grow after you exposed the cold wall sheeting?
the frost was there when i pulled off the vapor barrier and the insulation. I should aslo mention that the moisture is above the basement framing (bi-level) and seems to be in the area on top of the basement walls between the floor joists.

There are 2 heat ducts in the cieling blowing warm air into the basement along this wall, but the rest of the basement has heat ducts too, and its dry everywhere else.

here is a pic of the area in the home where the moisture is. The dark stains on the floor joists look like water stains, but are not.



thank you again for your comments
 

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Your structure has a bad air leak causing the frost and possibly a water leak looking at the left portion of the pic.

This is the only thing I can think of that could cause that---there are several insulation/ house sealing pros here---

Let's see if one of them has a remedy.
 

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I see from the send photo that you have insulation and vapor barrier along your rim joist. Just pushing the vapor barrier against the sheathing and stapling it in two or three places is not exactly an air-tight connection. So warm moist air from the living area got behind the vapor barrier condensed on the cold sheathing, and froze. Posssibly that was just a particularly bad spot. Might want to pull open a few more bays and see if they are all like that. My house is done the same way, so I am not saying the insultion was done inproperly, just that it is not perfect. This is an example that I would say is more likely to be close to air-tight....... although from a close look at that first photo, the air leak could be coming from the upper level.
 

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Discussion Starter #8
there are several insulation/ house sealing pros here---

Let's see if one of them has a remedy.
Thank You oh'mike

Here is some more info.

I cut through the drywall on the upper walls of the house above this frosty area and looked at the insulation and the sheathing. It was was bone dry above the area where the moisture is collecting. This should confirm there is no water running down the walls above this area into the lower framing.

The frost/water is only collecting on the exterior portion of the home the floor joists butt up to, nowhere else. It is only frosty on one side of the house. There is no snow or water build up on the exterior of the home that could melt and seep into the structure.

Thank you all again for your input.
 

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It could be as simple as SPS-1 described----warm moist interior air reaching that rim joist---

Air sealing might be the answer-----
 

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As a temporary test, and if possible, try taping plastic sheeting / visquine to the outside of the house in that location, a few feet in each direction of the frost area, to divert air infiltration and see if that frost diminishes to some extent. If I were a gambler I'd bet this frosty area is on the north side of the house.:)
 

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Also check to see if they ran the sheathing down past the foundation a min. of 1". You should never be able to see the top of the foundtaion from outside.
 

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1. The frost is on the engineered rim joist only, or on the rim and the top plate below?

2. Is the p.t. solid wood plate sitting directly on the concrete or is there a poly sill-sealer material between them? Could be wicking moisture from exterior grade; http://www.greenbuildingadvisor.com...ressure-treated-sill-plates-and-building-code

3. How long ago was the house built and did it rain a lot then? Could be wet lumber taking longer to dry between joists- no air movement, temperature difference, etc.

Tyvek requires taping and sealing for an effective air barrier.
4. What type of siding?

5. Any rain-screen air gap?

6. The air barrier on the rim joist should be air-tight as mentioned, foamboard/canned c.c.foam is best to stop infiltrating/exfiltrating air movement (either the inside poly is leaking or the outside air barrier (possibly taped sheathing) is));
http://www.buildingscience.com/docu...joist/files/bscinfo_408_critical_seal_rev.pdf

http://www.buildingscience.com/documents/digests/bsd-103-understanding-basements?full_view=1

Gary
 
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Discussion Starter #13
1. The frost is on the engineered rim joist only, or on the rim and the top plate below?

The frost is on the rim joist only, none on the top plate

2. Is the p.t. solid wood plate sitting directly on the concrete or is there a poly sill-sealer material between them? Could be wicking moisture from exterior grade; http://www.greenbuildingadvisor.com...ressure-treated-sill-plates-and-building-code

I don't know if the bottom plate has a poly sealer or not, I can't see it wicking from the final grade as the top of the foundation is 16 inches out of the ground

3. How long ago was the house built and did it rain a lot then? Could be wet lumber taking longer to dry between joists- no air movement, temperature difference, etc.

the house is less than a year old, it was not wet when it was built. The homebuilder is all over fixing the problem we are just trying to find the source of the moisture

Tyvek requires taping and sealing for an effective air barrier.

I can't tell its covered by the siding


4. What type of siding?

vinyl

5. Any rain-screen air gap?

sorry don't know what that is

6. The air barrier on the rim joist should be air-tight as mentioned, foamboard/canned c.c.foam is best to stop infiltrating/exfiltrating air movement (either the inside poly is leaking or the outside air barrier (possibly taped sheathing) is));

air barrier on the rim joist is fiberglass covered by plastic. Gonna have to take off the siding to check the outside air barrier


http://www.buildingscience.com/docu...joist/files/bscinfo_408_critical_seal_rev.pdf

http://www.buildingscience.com/documents/digests/bsd-103-understanding-basements?full_view=1



Gary
Thanks for taking the time to ask these questions.
 

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I see the answer above, vinyl siding.That was my fist thought when reading the thread. You are getting a leak , most likely at the bottom of the wall where the vinyl siding starts.On the exact opposite side of the frost or in the immediate vicinity look up behind the bottom course of siding and you will see the problem.
 

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Discussion Starter #15
I see the answer above, vinyl siding.That was my fist thought when reading the thread. You are getting a leak , most likely at the bottom of the wall where the vinyl siding starts.On the exact opposite side of the frost or in the immediate vicinity look up behind the bottom course of siding and you will see the problem.
The house is a bi level, so the bottom course of the siding is well below the area where the moisture is collecting. That said I wouldn't be surprised if it is an exterior seal problem.

Any suggestions on how to find an air leak into the house?
 

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The frost has found it for you. Look no farther, it's approximately centered on that frost area or slightly below coming in under the siding. When the wind drives against the side of the house the air is going to move left , right and up in this instance.
 

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There is little moisture in cold air, and Alberta air is about as cold as it can get. Thats why I am suggesting that is interior moisture condensing on a cold surface. Exactly the same as the frost forming on the bottom corners of your windows.
 

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Just because the house has Tyvek that doesn’t mean it was installed correctly and believe me, sloppy installs happen way more than you’d think. Even if it’s taped there is likely nothing sealing it at the very bottom.

I’d still want to see what the sheathing looks like on the other side of the wall at that spot. That type of inspection would be real easy to do with vinyl. But... with as cold as it is right now you need to be real careful with the siding. It will be very brittle and can break easily.
 

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Wouldn't the tyvec stop the wind from entering the home?

on another note,how do you send a pm to somebody here?
Not even close.

Tyvek, as it is normally installed, is just a bulk moisture barrier and not an air barrier.

There is little moisture in cold air, and Alberta air is about as cold as it can get. Thats why I am suggesting that is interior moisture condensing on a cold surface. Exactly the same as the frost forming on the bottom corners of your windows.
+1

All the moisture is from inside the home and it is just condensing and frosting on the cold exterior structure.

Just because the house has Tyvek that doesn’t mean it was installed correctly and believe me, sloppy installs happen way more than you’d think. Even if it’s taped there is likely nothing sealing it at the very bottom.

I’d still want to see what the sheathing looks like on the other side of the wall at that spot. That type of inspection would be real easy to do with vinyl. But... with as cold as it is right now you need to be real careful with the siding. It will be very brittle and can break easily.
+1

It will crack like peanut brittle. Don't even try if it is cold.

Fix the ribbon/band joist area.

Rigid of CC SPF is your friend here.
 
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