Hi Willy - We are under contract on our house and this issue came up. The attic rafter which I thought came up with inspection and you didn't think it was mold. Do we need to have it looked into further?
Willy's Reply: The bad mold (if you had a problem) would be on the plywood roof sheathing and on the sides of the roof rafters. The picture you sent could be mold but it’s from the lumber when the house was built. In a lumber yard wood sits outside and gets rained on. The lumber is not kiln dried, it’s what they call surface green and mold as well as other fungi grow on and in this “NEW” lumber. The mold (if it is mold) is dead but the wood has been stained. If the stain concerns you, get some white primer paint like “Kilz Max or Zinnsers' mold killing primer” and paint over the black spots. When a serious mold problem does occur, professionals spray paint the entire attic with these type of products to kill the mold. It also helps to prevent it from growing back. But mold can grow on virtually any surface, so the best solution is to reduce the moisture and the mold, which is a plant, dies. The dead mold stain is what it looks like you have on your roof rafter from your photo. Hope that helped.
Hi Willy, hope all is well.
Question - Do you think I should get my central air vents cleaned? The ones that run through the home? Thanks!
Willy's Reply: The short answer is NO. If your A/C ducts are made of plastic, they cannot be cleaned, and cleaning may damage the plastic liners. If they are metal, they may have some type of insulation inside them that can be damaged if cleaned. Even if they are unlined metal ducts, there have been studies that show if left undisturbed, dirt and dust that builds up inside ducts develops a hard shell over it. This shell harmless unless disturbed by cleaning and sometimes cleaning releases more dust and mold spores into the air.
Now there are conditions where you should clean the ducts - If there has been a fire in the home, it’s a way of helping to get rid of the smoke smell. If there is a continuing mold problem, then definitely clean the ducts. If there is a high moisture problem in the basement, the moisture can support mold growth inside the ducts.
The best thing you can do is change your air filters in the heat and A/C system about every two to three months. I tell people to use the 3-M Filtrate pleated air filters with a merv rating of 8 (see pic above). They remove 99.9% of all the dust particles in the supply air. Because they are so efficient at removing dust they clog quicker than a fiberglass filter, so you must remember to change them more frequently. If you have pets like dogs or cats, then you will need to change them more often as well.