What Would Cause False-Positive Mold Test in Attic???

We recently did a mold-test kit in our attic because we'd had some areas along the outer edges of the attic floor where the insulation (blown-in) had somehow been moved out of place, and on our ceilings, shadow/gray blobs appeared. We had a couple of contractors take a look, and they believed the gray areas on our ceilings were caused by the lack of insulation in those specific areas, due to the temp difference in the attic and in our living space. They advised us to move the insulation back into place, and clean/wash the gray/shadow looking areas on our ceilings and paint over them if need be, and see what happens. Well, most of the gray came off when scrubbed. However, we were still concerned about the opportunity for possible condensation to present itself. We waited a few weeks and did a do-it-yourself mold test kit (petri dish) that we bought at Lowes for $10.00. It came back positive and a few different colors of mold grew in that dish. However, we cannot see or smell ANY mold in the attic. This is a regular 1,000 sqft rectangle-shaped ranch house - nothing extraordinary. Anyone know why a mold test would come back positive when we can't even find it or see it? We're stumped. Attic is well ventilated, with vents in both ends of the attic, and an attic fan at one of the vents. Also had a new roof put on three years ago, and NO leaks. We're stumped.

 

I wouldn't be so quick to say that it's a false positive but you can buy a test kit made by a different company to confirm or deny the original results.

 

I am not an expert on mold, they get the big bucks, but mold is everywhere and you can never get rid of it. That said, you can stop feeding it, food and moisture. Wood is food, so that makes it difficult to eliminate it in your home. But the moisture can be controlled. Air sealing between your house and the attic will greatly reduce the amount of moisture delivered from below, which can find a cold surface and form condensation. Air sealing also reduces your energy costs, see link below.

Your attic fan is not helping, as it can draw warm moist air from inside your home up through all of those leaks. Sealing them will reduce the effects of the fan.

When insulation is blown away from the soffits, it can be due to wind blowing in those soffits. They recommend a baffle to shield the ends of the insulation.

You have removed the visible part of the mold, but it is still there embedded in the wood. Hurricane Katrina taught a lot of people about encapsulating. Fosters products can cover the wood to hide it for ever, we hope. But the real solution is to eliminate the moisture and most of that is probably (guessing) coming from inside your home.

Bud

http://www.efficiencyvermont.com/ste...ide_062507.pdf

 

Not sure why you would call it a false positive, but at any rate, almost anytime you do a cultured mold test in a petri dish, you are going to get mold. As Bud said, mold is everywhere. Makes me think back to when we did that in Biology class years ago, touching different household items to the gelatin... and everyone's dishes grew mold. Was there mold actively growing on any of the items that students touched to the dish? No. But mold spores are everywhere. Give them the right conditions and they will grow.

So eliminating the conditions that might grow mold is your priority. Adequate insulation will help prevent interior surfaces from reaching the dew point. Frost often occurs in attic spaces, so your attic space is another issue entirely.

 

Thanks for your response. I called it a "false positive" with the idea that a positive test would mean active mold growth in the attic. As I stated in original post, we can find NOTHING. To me, that makes me think the test should have been negative. We called the company's phone # in the test kit, and they swear up and down that if there's "enough" mold in the air that the petri dish catches it, then there's "definitely mold growing in your attic and it needs to be addressed" --- but again, we can find NOTHING. That's why I called it a "false positive".

 

Thanks for your reply, Bud. We hadn't thought about sealing any "leaks" such as areas where ceiling fans are installed, etc. Thanks for the link. We still can't find any mold growing on any surface, and cannot identify any other sources of moisture.

 

p.s. to Bud: When you said "You have removed the visible part of the mold" --- it wasn't mold that we washed off the ceiling areas. It was dust/debris/other particulates in the air that "stuck" for lack of a better word, to the cold spots on the ceiling where the insulation in the attic directly above said spots had been moved/blown out of place. We examined the gray/shadow looking places on the ceiling up close and personal, and it was not mold. Also got up in the attic and dug through the insulation all the way down to the drywall ceiling - and still no mold.

 

Mold is everywhere. There should be more mold outside than inside. Your attic is open to the outside. that's where the mold is coming from. You could do a test inside and get the same results.

 

By the way the test from the DIY stores really don't tell you much.