basement insulation - vapor barrier help please!


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Old 04-06-11, 06:17 PM
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basement insulation - vapor barrier help please!

Hello everyone,

Let me start off by saying I have no clue what iím doing. I decided to finish a rec room in our basement. This is an old house with concrete block walls that were previously painted with latex paint.

I went to lowes and asked a random person about what type of insulation I would need. He suggested faced batt and then asked if I had put up a vaper barrier between the wall and the frame. I said no but if that is the best way to go I can still do that without too much trouble. Long story short, here is my current setup which after looking on the internet seems to be a terrible one.

I wrapped the back, sides, top, and bottom of my frames with plastic sheets I got from lowes. I have the frames directly against the concrete blocks. I then added the r-13 insulation with the paper facing the inside, and drywall over top. so from inside out I have drywall, frame/insulation, plastic sheet, block wall.

The basement is fairly dry. The few spots suspected of any moisture had drylok applied. There is a ledge about 5 feet from the ground that moves the wall out about 4 inched to the outside, so the upper two feet of the frame is not touching the wall directly leaving 4 inches of space between the wall and frame. My location is NE Ohio

I am kicking myself for just trusting someone and not doing any other research. Do you see any way to salvage this setup or do I need to remove the drywall and the vapor barrier. If it is possible to leave the frame against the wall what do you recommend using?
Any help or suggestions are greatly appreciated.

Thank you!

oh, forgot to mention the setup is pretty much the same as this guys youtube video
YouTube - How to Install Vapor Barrier
 
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Old 04-06-11, 06:53 PM
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I'm not understanding what the problem is exactly. It sounds like all the moisture is contained behind the vapor barrier and the cement wall has latex paint which breaths. The wood is in contact with the plastic sheet. The only possible problem is if you put kraft insulation and created a double vapor barrier, and even that shouldn't be a big problem unless there is obvious water. If you feel concerned, cut a small slice in the drywall at the top and the bottom and rip out some of the kraft. I would leave it though.
 
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Old 04-06-11, 10:39 PM
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If you are getting moisture behind the vapor barrier there would be two sources. Either you are getting water entry through the outside wall, or your vapor barrier is not properly sealing the insulated wall. Vapor barrier is used to control air flow, and what you don't want is warm inside air flow meeting cold outside air, or condensation will occur. I have read that even a 1/4 inch hole can produce a cup of water a season. To keep this from happening it is best to completely seal the vapor barrier along each joining surface, ie. floor, and sill plate. You can use accoustic sealant for example to do this. Ridgid foam insulation instead of batts provides both a thermal break verses thermal barrier as well as when it is also completely sealed provides complete control of air flow between warm and cold. In basements ridgid foam or the more expensive BASF type spray foam is the best way to go. There are many basements finished in the past with batt insulation and insufficiently sealed vapor barrier that smell more like a swamp than a liveable space.
 
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Old 04-07-11, 12:43 PM
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Thank you for the replies.

It seems everyone has conflicting views on this issue, but it does seem that the best way to have gone would have been to attach and seal foam boards to the wall, then put the frame up against that.

I have read that with the setup I have now, since the plastic is touching the cool concrete block wall, condensation could happen on the inside of the plastic and then be absorbed by the insulation creating mold. Does that make sense?


Some people seem to think i'd be fine the way it is now and others act like it could not be worse. It is very confusing.

I think I can at least take down the drywall sheets and remove the paper facing from the batt. Everyone seems to agree that having the paper in basement walls is a bad idea.

If I were to put foam board against the cement block now it would be a big hassle since electrical outlets/wires and drywall are already in the frame.

Do you think it is worth removing all that?

To seal the sill plate, do you just need to put a bead of caulk where it meets the floor?

I really do appreciate the reply.
 
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Old 04-07-11, 11:08 PM
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Make sure that your top sill plate is well sealed where it meets the foundation wall. Not sure if you have a gasket or not on that plate depending on the age of your house, but any gaps can be filled with spray foam from a can, and you could caulk if needed also to eliminate cold outside airflow. If it is not well sealed alot of cold air will pass through that area. If you don't have any obvious moisture problems from your foundation walls I think at this point it would be better for you to apply the vapor barrier on the inside of the insulation behind the drywall to at least eliminate any warm moist air flow from entering the wall cavity and causing possible condensation especially near the sill. I would try and secure and seal the vapor barrier at the top, all the way up between the floor joists, and along the bottom wall plate with a product like accoustic sealant running complete beads to attach the poly. Are you doing anything with the floor pad in regards to a thermal and moisture break? In the end it all comes down to budget and what results you can live with.
 
 

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