Mildew Problem and insulation

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  #1  
Old 03-23-03, 12:42 AM
Kirkwa
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Question Mildew Problem and insulation

I am remodeling my home, in the process of re-dry walling; I found that the exhaust pipe came off the upstairs bath vent. A black dust, (I think is mildew) formed on the plywood in the attic, and thought out the blown-in insulation. Based on what I have read, and on the recommendation of a friend, I clean the area with bleach, and water.

The plywood looks brand new. I am going to replace the blown-in insulation. To my question, I also found a black discoloration on the R19 insulation batting in the exterior walls. There is no water damage or wet insulation. Should I replace this as well or will it be fine to re-install and cover with a moisture bearer?

On the other hand, can the R19 batting be treated, and reinstalled?

Thanks Kirkwa
 
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  #2  
Old 03-23-03, 08:38 AM
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Wait and see.

The discoloration of the plywood maybe either because of the plywood being wet or mold/mildew growth. In either case since you have addressed the source of the moisture. The moisture, mold or mildew will go away. Let the area of concern dry out and then try brushing the area clean.

The black dust in both kinds of insulation indicates air movement. The insulation acts as a air filter, trapping the dust inside the air as it moves through the insulation. The cellulose indicates the leaky bathroom vent as being the source and you have apparently corrected the problem.

The wall fiberglass insulation is a different story. The source is probably wind pressure and this usually occurs near the top of walls because of overhands or eaves. These act as a dam when the wind blows against the wall, forcing the air into the wall. A telltale sign is this black colored dust found in the insulation. This by itself is not a moisture problem. It is when this interacts with other applications inside the structure that it becomes a moisture problem. An example of this is cooling the home and the outside is warm and humid and the wind is blowing hard against the house. Since warm humid air condenses against cooler surfaces, as this occurs while cooling the home, the warm humid air from outside will penetrate the wall and condense inside the wall once it reaches a cool enough surface.

The solution is to apply an air barrier to the outside of the structure such as Tyvec. If this is not feable for you and the cavity of the wall is only open to the inside the structure, then you can apply the air barrier first against the outside wall, then install the insulation. However, in order to make sure the effectiveness of the air barrier, you have to staple and tape with a qualified tape the sides, top, bottom and seams in the air barrier.
 
  #3  
Old 03-23-03, 04:02 PM
Kirkwa
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Question Meldew Problem and insulation

Thanks you for your quick response! The reason I posted my question was simply confusion on my part. I was not sure if the discoloration in the wall insulation was mildew, and what would cause the infestation. I should tell you the discolorations are not limited just to the top of the walls, and just around the bathroom area. There are black spots throughout all the upstairs wall insulation, top, bottom, and middle.

Let me be sure I understand you correctly on several points. If this is dust in the insulation, and is caused by a situation such as you’ve described. How do I determine this for sure? I read if you spray the infected area with bleach/water then waiting several minutes, and it dues not go away. This is a good indication it is not mildew. I did the following based on some research.

As I stated, this same discoloration was on the plywood, (black dusty substance) and the bleach/water solution salved the problem. I sprayed a small section of the wall insulation, (black spot) with the bleach/water solution to determine if this was the same substance. The bleach/water solution bleached the insulation white all around the black spot but did nothing to change the color of the black stain.

Question:
Is this a good test in determining whether the discoloration is something other than mildew?

Question:
Regardless what the discoloration is, should I replace the insulation?

You mentioned “Tyvec.” I’m assuming you are referring to the house wrap that provides an air infiltration barrier. If so I had not planned to re-side my home, and as you have described, this product is applied to the exterior of the home between the plywood, and siding. Correct?

Question:
Are you suggesting I staple/special tape this product between each wall-stud on the inside, and then install the insulation. Alternatively, a continues piece between, and over the wall studs, then insulation?

Question:
If I use the Tyvec, is plastic needed over the top of the insulation before I drywall?

Thanks Kirkwa
 
  #4  
Old 03-23-03, 09:43 PM
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Moisture is the best test.

Mold and mildew cannot survive without moisture. Remove the source of moisture and the mold and mildew goes away. I disagree with the use of bleach and water on laminates because you can inadvertently delaminate the plywood. In reality one can test for the presence of mold or mildew but the elimination of the source of the mold and/or mildew is the solution. Furthermore, moisture control is not only a solution but a preventive measure. In other words you can test for mold and/ mildew you still need a viable solution and an action to prevent it from reoccurring. In this case the preventive action is the same as the solution, moisture control. In my opinion, there is no need for testing.

Since the black spots were found throughout the upstairs walls and not being confined to a particular area we step into a realm that I find difficult in explaining to individuals who are experienced in this industry. The black spots without question is dust and is a direct result of air infiltration. An air barrier applied to the outside of the structure is the most common and accepted solution. However, in the vast majority of cases, the cause for it is the attic by-pass phemonenon and air leakage. Examples of this are poorly closed attic entrances, whole house fan louvers in hallways, recess lighting, and absences of closing dampers on exhausts fans.

From here I would have to consider the different schools of thought. One would be that in the absence of mosture the dust (black spots) in the insulation is a natural occurrance and in the winter could assist in the drying out process of the structure. Another school would point out the potential for mold and/or mildew. The spore for the growth of mold and mildew are in the dust, all you need is moisture. Air conditioning could produce the conditions required for condensation.

There is a big difference between over-reacting to a potential problem than providing a practical solution. In my opinion since the walls cavities are open, I would not recommend re-installing the old insulation. I would recommend installing fiberglass insulation that is encapsulated. Manville makes such a product where plastic surround the fiberglass. I know what you're thinking, vapor barriers being on both sides of the insulation. If you look at this product, you will notice the plastic on one side is heaver that the other sides of the insulation. The thinner plastic meets the five times rule concerning vapor barriers. In other words this thinner plastic has a more than five times perm rating than the vapor barrier and will not trap moisture inside the insulation. What the thinner plastic will do is prohibit the air infiltration that carries the dust and spores. The probability of mold and mildew growth will be greatly reduce.
 
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