condensed water in the attic floor


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Old 01-12-12, 07:00 PM
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condensed water in the attic floor

I have read alot of usefull related posts on this issue before raising this question. I 'm amased how little I know the science behind ventilation/insulation and warm vs cold air phenomenon.

My favorite posts so far are of bud9051, redhouse, xsleeper and more.

My question is, regards to my existing issue with water in the unfinished attic floor to which many posters have given very good explainations and answers, will the water problem go away if I finish the attic and turn it to living space providing I would do what it take to properly insulate and vent this new addition?. Its too late to fix the inside of floor because 3/4" OSB were glued and nailed down through out the floor perimeter.

Your inputs will be appreciated
Thanks
 
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Old 01-13-12, 03:09 AM
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Assuming the moisture is not water leaking through the roof above, then it is moisture condensing on the floor or on the bottom of the roof above and dripping down. Often the nails that protrude through will frost up, then melt and drip. In any case, it is then moisture from below being carried into the attic through air leaks. With the OSB in place you will have trouble accessing the ceiling below where the air sealing needs to be done. As al alternative, less effective, you can seal the leaks in the basement if you have access. Plumbing pipes and chimneys often pass basement to attic. I'll add a link on air sealing so you can try to identify the major leaks and consider it cutting away some of the osb would be worth the effort to access the area below.

The humidity inside your home can be reduced and make sure any bath exhaust fans are venting all the way outside. There should also be venting into and out of that attic space.

Bud
 
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Old 01-13-12, 07:26 AM
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Thank you Bud for a fast reply. The water is not from leaking roof. It 's from condensation inside the floor. I happened to cut out a small piece of the floor to access electrical wiring and found the cut piece wet on the inside. I have no idea how extend it is through out the floor.

Will the condensation go away once I finish the attic as heated living space?, taking into account that I will do the best sealing holes and opennings from below and understanding that this addition will need to be properly vented and insulated as suggested by your previous posts?
 
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Old 01-13-12, 10:46 AM
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It should, but do a very good job of blocking any air flow from outside walls into the ceiling/floor cavity. I. E. if you install knee walls, then one option is to block the cavity below the wall and insulate those cavities over to the outside wall.

The problem at hand is the current moisture. Left unattended, mold can get started in 48 hours and I suspect you are well past that. If you sampled each joist bay and only some were wet, that might give you some idea as to where the problem is coming from. Can lights, electrical boxes, drop ceilings, plumbing pathways, are a few. Use the efficiency Vermont link I'm sure you have seen as a guide. Just a thought, but a 2" hole saw might be able to create some ventilation for those cavities below and could easily be parched later, assuming that isn't going to be your finished floor.

Bud
 
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Old 01-13-12, 04:27 PM
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You are on top of things. Yes, there are knee walls but I consider not to insulate the knee walls, instead I will insulate the rafter cavities all the way to soffits using baffling chutes for air flow between soffit and ridge vents. The roof has a 12:12 pitch, 2x8 rafters, 4ft knee walls, 5ft slanted cathedral ceilings, and 8ft flat ceiling with small attic on top. The knee walls will have only sheet rock. I will sheet rock under the roof outside the knee walls that way the joist cavities below will get warm.

Pleass tell me if I didn't think right about this idea.
 
  #6  
Old 01-13-12, 07:14 PM
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Sounds like you're on track. Take a look at Roxul instead of fiberglass. Very dense and great properties. They have a locator to see if it is available around you.

Bud
 
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Old 01-15-12, 10:38 AM
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You write that it is condensation?
Therefore, you know that the warm wet air inside your home is escaping into the space above the ceiling, is meeting the cold air and wood etc; up there and condensing.
Once you turn this space into part of your comfort zone, the problem will move elsewhere.
The best way to proceed is to make sure that the new walls and ceiling are insulated to a high standard, this will move the condensation onto the windows where it can be wiped dry.
Sheet polystyrene or blueboard or similar forms of closed cell insulation will give you the best result from a cost ease of fitting view.
Make sure that the insulation is at least 50% better than that recommended for your area, this will reduce your heating and cooling costs.
As standards rise, the recommendations are always being upgraded.
 
 

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