moisture behind insulation


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Old 01-18-05, 07:37 PM
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moisture behind insulation

I have an unfinished room above a downstairs bathroom. There is insulation in all the 2x6 studs and vaulted ceiling (which also has baffles, a ridge vent and soffit vents).My problem is there is frost behind the insulation, especially on the north side of the room and also some in the ceiling and now that it has warmed up it is melting and coming in the downstairs room through the ceiling. What is the matter?? I did not have this problem last year at all. Should I have a plastic vapor barrier on the walls and ceiling in addition to the kraft paper on the insulation? I hope to finish this room next winter.
 
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Old 01-18-05, 08:42 PM
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moisture

You didn't happen to have installed a vent fan in that bathroom since last year ? I'm thinking a vent fan may be improperly discharging into your unfinished 2nd floor room. Just a thought.
 
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Old 01-19-05, 12:14 AM
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High Humidity? Air flow?

Taking into consideration of the last comment I need to ask if this bathroom is complete with shower and or tub and is it used frequently. This could explain raised humidity levels. Then of course the exhaust fan, is there one and where is it being discharged.

If there is moisture then your insulation may be compromised and if this is the case your insulation isn't performing very well if at all as water makes a great conductor.

The fact that this did not happen last year does not necessarily mean the problem did not exist. It may have increasingly gotten worse. Were the conditions identical (inside and out)? Perhaps your insulation has continued to take on moisture all year.

Is the insulation exposed in any way? Can convection currents flow through any spaces where the insulation is installed? Perhaps warm are is permitted to flow through any gaps to the exterior walls. What is the substrate of the exterior walls, wood, metal, concrete?

Another problem may devellop, mold.

If so this company has some interesting information: www.oceanairsys.com or if you want to research "thermal dynamics" there is some interesting information here: http://www.eaglecoatings.net/content...l/Tutorial.htm
 
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Old 01-19-05, 04:46 AM
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reply

Yes there is a vent fan in the downstairs bathroom that is vented to the outside wall from the suspended ceiling.It is a large one, don't remember the cfm's.This bathroom also has a shower that is used everyday.The substrate on the exterior walls is wood. Would a dehumidifier take care of this problem for now till I get the upstairs room finished? The insulation is exposed in the studs upstairs yet and should this be covered with a plastic vapor barrior so warm air can't get behind the insulation and freeze?
 
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Old 01-19-05, 09:38 AM
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similar problem

Is that frosty N. wall an exterior wall? My guess is that it probably is.

I'm sure that a qualified professional on-site could bring a lot more to

this discussion, but I had a similar problem several years ago that resulted

in structural framing damage. After fixing the damage and doing some

"band-aid" fixes to insul. and ventilation, I had the same problem all over

again in a couple years, this time with worse damage. After a lot more

research into the cause of frost behind insul., I decided this time, after

rebuilding the entire wall, to put a layer of 1/2 " polystirene foam board

on the outside, before putting new siding on. It's been almost three yrs.

now and not a hint of problem anywhere. Some people advised me not

to use this method because of fears of creating the very problem I was

trying to correct. There may be a less invasive cure for your problem and

I realize that most homes do not use 1/2" poly on the walls and have no

problems, but this was one of those rare cases when the (foam)

manufacturers recommendations worked in spite of "conventional wisdom".

Just a thought, good luck on a simpler fix.
 
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Old 01-19-05, 10:07 AM
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No matter how hard you try you cant get a seal for a good V/B with just the paperback on the insulation. That is why we always staple the paper on the inside of the studs . When its all up walls and ceiling then we put a 4 mil poly over the walls as one piece and the ceiling as one piece. id take out what you have and let dry them put up new insulation.

ED
 
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Old 01-19-05, 10:14 AM
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Thanks

everyone for all the help!
 
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Old 01-19-05, 01:38 PM
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another two cents worth

One of the places I worked at had a bathroom that was in a disgusting condition. There was black mold in the mushy drywall around the tub and below the window. The ventillation fan was noisy and was set to go on each time the light was turned on as this facility was frequently used.

We called in a company called www.oceanairsys.com who specialize in air quality control and mold remediation. After removing and replacing the dw these guys removed the fan entirely and installed a "Passivent" which is a vent that works automatically without power. It reacts to humidity and will open when the levels are high and close when they return to accepted normal levels. The advantages are of course less energy used and the humidity is automatically removed. There is no need to guess how long you need to keep a fan on. The walls were coated with a liquid ceramic insulation coating (Super Therm) to prevent condensation from develloping on the walls and ceiling. Six months later the bathroom is in great condition. The walls and ceiling stays dry. The vent does indeed open and close by itself thus we are not losing much needed heat.
 
 

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