Mildew and mold problems
We are currently remodeling our 1947 vintage home in Austin, Texas. It is a pier and beam and we have been having a mildew/mold problem. I have cut some additional vents in the crawl space and am presently laying a 6 mil. poly liner and also insulating previously uninsulated walls. Do you think this will take care of our mildew/mold problem? Are there additional measures that we could try? After we add the insulation, should we also add a vapor barrier?
It's hard to pinpoint a solution for a mold and mildew problem because you're really asking a two-part question. First, you need to address the mold and mildew. Second, you need to incorporate proper ventilation into your home to prevent further outbreaks.
If you don't quite understand how mold and mildew develop, let me give you a brief overview. Mildew and mold are part of the fungi group. Unlike plants, fungi do not produce their own food so they must derive their nutrients from the animals, plants, or decaying matter on which they live. In your case, the household paints are probably over ten years old and can no longer resist the fungi.
To get rid of mold and mildew requires a few chemicals and a lot of elbow grease! Wash your walls using a mixture of 1 cup trisodium phosphate (TSP), 1 quart liquid laundry bleach, and 3 quarts of warm water. When the surface is clean, rinse with fresh water. If TSP is not available in your area or its use is prohibited because of ground water regulations, your paint dealer can suggest an environmentally safe product.
Let the area dry for at least one week, depending on the time of year and the humidity, and then repaint using paint containing an anti-mildew additive. Again, your paint dealer can suggest an appropriate product.
In a high humidity climate, it is possible that mold/mildew can begin inside the stud cavities and actually permeate wallboard, appearing on the interior side of the wallboard. Unfortunately, wallboard removal and replacement won't really solve the problem because in a humid climate there's no way to actually dry out stud cavities. Depending on the level of damage, studs will need to be removed in this area or—in an extreme case—the house may need to be torn down.
Normally when mold and mildew appear in a home it's because the home was built so tight it doesn't have proper ventilation to breathe. In your case, you might have to install an air exchange unit or an electric ventilation fan on the roof or at each gable end. If there is excess moisture on the interior side of the windows, then you need to install a portable dehumidifier. It's important to check with your local building department to get requirements for your area to properly ventilate your particular structure.
Adding the 6 mil. poly liner in the crawl space will help with normal moisture but not with standing water from runoff or an underground spring. Eliminate this with a sump pump. However, redirecting water due to rain and snow runoff away from the home will prevent water from depositing in the crawl space. Make sure you use a black poly liner (not clear) as it will hold the moisture to the ground.
Mold and mildew result from excessive moisture, and ventilation's role is to ensure the removal of excessive moisture from the building. It's important to properly ventilate bathrooms, laundry rooms, and kitchens—these rooms are more prone to moisture than other rooms in a home. Another area of concern is an uninsulated AC duct, where the possibility for moisture is great.
Finally, when does the mildew appear—during the summer because of air conditioning, in the winter because of condensation, or both? As you plan your insulation and vapor barrier, consider the following:
To learn more about moisture and mold, go to Johns Manville and type in their search engine the following: "Technical Report by Larry Gelin Moisture and Mold Growth." The .pdf document brought up titled "Not in my Building; Moisture and Mold Growth and the Specification of Wallcovering" is very interesting.
The U.S. EPA, Office of Air and Radiation Indoor Environments Division (6609J) offers a document titled "A Brief Guide to Mold, Moisture, and Your Home." This guide provides information and guidance for homeowners and renters on how to clean up residential mold problems and how to prevent mold growth. Click here to go directly to the source on their website.