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Attic mold - vapor barrier necessary ? Hearing conflicting things

Attic mold - vapor barrier necessary ? Hearing conflicting things


  #1  
Old 01-20-05, 10:09 AM
spspsp
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Attic mold - vapor barrier necessary ? Hearing conflicting things

Hi All,
I have read many threads at length. Thank you very much for your help.

We purchased a house 2.5 years ago, and after purchase found an extensive mold problem on the roof decking. Long story short, we had to eat $ 10,000 and rip off all the decking and re-did the roof. We have an 1500 sq ft attic we put in 16 soffit (8 double sections per side) vents and a continuous ridge vent

1 year goes by on the new roof, and the first winter, there's ice all over the interior decking. I call the roofer, he states that it was due to the extreme cold, and not to worry. No mildew / mold in the spring. So I blocked it out as bad deja vu.

This winter rolls around. I hadn't been up there since the Spring, but upon my first visit, Mold is all over the brand new decking.

I had insulated with unfaced r-25 - which I know is a little light on the r-value - i wanted it to breather freely though. Upon finding this new problem - I called the roofer. Thankfully he is fairly open to come over and check it out. I also phoned an insulation guy; as I had read online, that a vapor shield is necessary.

He stated it was not. He has said, even if a sauna was under there un-shielded, the roofer having just redone the ventialtion - his setup is not working as the r-25, although unfinished, should not let enough moisture up there to mold in 1.5 years.

I am going to lay poly plastic tonight under the r-25 - in hopes of doing all I can to stop this problem before it gets worse. I pre-cut all my strips at 16" to fit in the joist channels - is this ok ? Should there be overlap up onto the joists ? I have already painfully, financially and physically, re-laid the perimeter of the roof with new r-38, with a kraft faced barrier.

In the Spring, also I plan to bleach the mold. Or should it be done now, as it is frozen and not as "sporey"?

Thank you all for any thought and help !!!!!!
 

Last edited by spspsp; 01-24-05 at 10:59 AM.
  #2  
Old 01-20-05, 01:59 PM
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Do put a poly V/B under the insulation there. There also is a paint that you could use on the ceiling thats help work as a V/B there also. Now you said you put vents in the over hang there. So did you put the foam rafter vents in also so that the air from the over hang can get up over the insulation it has to you know. lots of times like that R 25 will like block the air from the overhang. You have no bath vent fans blow out up there do you??

ED
 
  #3  
Old 01-20-05, 06:33 PM
J
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Yes. Install vapor retarder on the warm side of the insulation. Too bad the original builder didn't put it behind the drywall. I am suspicious about your soffet venting. The intake has to equal or exceed the exhaust (ridge). Nice, big, screened holes are great. The code venting ratio is 1:300 min, 1:150 is better. An inch of overlap onto the side of the joists is fine. Don't let any of the vapor retarder be exposed to the cold attic air, buried behind insulation only.
Ed, I don't think he has vauted ceilings.
Jim
 
  #4  
Old 01-20-05, 06:41 PM
J
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I just thought of a few other items. Like Ed said, check all fan vent ducting(bath, kitchen & dryer). Check for cracks in your drywall ceiling and caulk. Check to make sure any electrical fixtures are sealed tight and have vapor retarder over them. Check flue ducts in the attic.
Jim
 
  #5  
Old 01-20-05, 07:00 PM
spspsp
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Thank you very much guys for all your insight and help I began to lay the v/b tonight. Also, I turned off the furnace humidifier. In turning that off 2 days ago, it's seemed to dry out up there quite a bit already. There used to be ice on the roof deck nails, there is no longer, as well as some of mold actually looked to be drying !!!!! I will continue laying the v/b as well as while the mold is unfrozen I'm gonna hit all the decking with some bleach.

Thank you again very much !!!!!
 
  #6  
Old 01-23-05, 08:12 AM
J
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Himebild, I don't agree. Please see my comments below:


"I am bothered by the advice you have been given to date since it is largely inaccurate and shows only a poor comprehension of the problem and an even poorer anaysis on how to correct it.

First, it is rarely IF EVER proper to add any type of "vapor barrier" to an attic after insulation has already been installed. The guy is replacing insulation, so it has not been installed yet. The code required (International Residential Code, Section R322) vapor RETARDER should be well protected by the R-25 insulation in all but the coldest climates of the US.

As previously mentioned, drywall, paints, laths and other materials already ACT as vapor barriers. Poor ones. According to the NRCA Roofing & Waterproofing Manual, 5th Edition, Vol. 3 a vapor BARRIER is a waterproof membrane and must have a perm rating of 0.0. Vapor RETARDERS must have a perm rating of .5 or better. ˝” drywall’s perm rating is 50, almost useless as a vapor retarder or barrier. Some paints may qualify. Plastic sheet barriers should rarely if ever be used because they will only contribute to future condensation problems.

Second, unless you seal all ducts, chases, conduits, wires, cables, chimneys, doors, hatches and any other opening between the living space and your attic....you will still have excess warm air entering your attic space and continued moisture problems. This is exactly what we said…seal all cracks and joints.
Third, the goal is to reduce moisture. You can do this by eliminateing excess moisture into the cold attic space from warm living space below as has already been mentioned:

1) Adjust humidifiers on forced air heat systems
2) Eliminate dryer and bathroom ducts terminating in attic spaces. Code requires all of these to exhaust outside of the building.3) Seal all holes from ducts, chases, conduits, wires, cables, chimneys, ducts between the living and attic space with approved foams or caulks. This is exactly what we said…seal all cracks and joints.

But the bottom line is that adding additional vapor barriers in an sttic is rarely if ever a proper solution especially if you try to install any type of a "plastic" vapor barrier. This is not an “additional” vapor retarder, just the code required one on the warm side of the insulation."


imho,
Jim
 
  #7  
Old 01-23-05, 08:14 AM
J
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I guess I don't know how to use this board. Tried to underline & bold my comments, but it just inserted [B] & [U]. My comments are between these marks.
Jim
 
  #8  
Old 01-23-05, 04:54 PM
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homebild Read how and what he is going to do

First, it is rarely IF EVER proper to add any type of "vapor barrier" to an attic after insulation has already been installed.
ED
 
  #9  
Old 01-24-05, 05:03 AM
J
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Homebild, spspsp is NOT in Florida. He has ice in his attic! He is above the 40 degree line on both the ICC climate map and the NRCA one. Code requires a vapor retarder on the WARM side of the insulation. Look it up in the references posted above. Show me a test result from a house paint that gives a perm rating of 0.0, qualifying for classification as a vapor barrier. You can't, because there is not one. It takes a BUR or single ply to get it. If house paint could qualify as an ICC vapor barrier, the paint companies would be selling and advertising like crazy! Vapor retarders slow the rate of water vapor movement, vapor barriers prevent the movement of water vapor. You need to study the NRCA Roofing Manual because you Do not know this stuff. I have been calculating dew points in wall and roof assemblies for over 25 years and understand the situation crystal clear. How else would we know how much insulation to specify? Also, please get some manners and be polite.
Jim
 
  #10  
Old 01-24-05, 08:01 AM
spspsp
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Update

Hi Guys, Again let me thank you all for your input and advice. I wanted to give an update as to what I have done, as well as some more spec's on the environment.

The home is in Northern Ohio - it is gas heated - the area in questions in an unfinished attic served by a hatch entry in a hall - it has a continuous length ridge vent served by 8 dual panel sets of soffit vents down each side (so 16 panels down each side - the area is approx 1500 sq ft. - there are 2 shower vents - but both vent via flextube hosing to outside roof vents

Around the perimeter I removed the unfaced r25 and replaced it with faced r38 - this then covers approx 4' in from the sides - all soffit vents are completely unblocked and show plenty of light through them.

Under the existing unfaced r25 - I have cut 18" wide 6 mil Poly sheeting and taken up the r25 - laid the plastic sheeting - then relaid the r25 back in over top.

On the product box of the Poly it did clearly state vapor barrier as a use for it.....

All top plates / romex chase / light fixture have been covered...by both Poly and then insulation - I see I may want to spray them still with foam though - I have not done that as of yet.

This new poly sheeting then, I placed under the r38 faced overlap by about 4 inches at the ends - packed the r38 back down snug.

The r25 which was removed from those preimeter areas - is now laying perpendicularly over several of the bedroms as a 2nd layer to bring those areas up to an r50 value - as r48 is spec'd for our area.

The areas which appear to be the possible culprit of the moisture - are the bathrooms - it appears their drop down soffit areas - above the shower stalls, as well as lighting areas - were left wide open up to the attic. Lighting cans had been replaced with airtight ones last year. It does also appear that they may have used standard drywall and not green board when the old owners had remodeled Also, it appears after this remodelling they did not insulate the walls - so when that humidifier was turned up, it had a fairly unobstructed path up and into the attic....

Above those areas however I removed all insulation and stapled the plastic sheeting over the channels - on all sides and ends - then laid the faced r38 back over top - hopefully "doubling up" the vapor protection. Also in one of the soffits I laid some r13 w/ kraft face on the soffits painted wall - the other 2 sides of the soffit are vinyl wall paper'd (which was stated to be a vapor barrier).

I have also shut down the house furnace humidifier - this is noticeable as several first floor wiondows now show no condensation - they used to however with the humidifier on. I did also speak to another friend who had said their humidifier was causing huge moisture issues. In our scenrio, with those open drywall soffits - I can only assume, this heat and moisture was simply rocketing up into the attic. Also, the humidi may have been even set a little higher than it should've been too - thus again point a finger at it as being a contributor - I won't say which finger I'm pointing at it though

The attic is now cold, and within the 2 days from completion some of the mold in the less condensed areas, looks to be visibly drying and hopefully die-ing. I am hoping and assuming the others areas will follow - it's just less noticeable as they were more "developed" in their growth

I do plan to paint the bathrooms with an oil based vapor locking paint in the Spring - to further supplement the v/b protection - I can't now as there is an infant in the house.

The bathroom main walls are wall paper'd with a vinyl paper, so the walls I believe are OK, it's the ceilings which are of concern. This then would in essence give me nearly a "triple" barrier in some areas.

Again, thank you all very much for all your help and advice, any and all of it is greatly appreciated !!!!

If anyone can offer their opinion as to my courses of action so far, please do so. Thanks !!!!

==============================

Thursday 1/25 evening update - sprayed all mold on decking with pure bleach - this then will let me adequately gauge in a week or so, if growth has stopped, or if it begins again post-barrier install.
 

Last edited by spspsp; 01-25-05 at 07:03 PM.
 

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