Is Mold Creeping into Your Home?

Jeff Bookout
May 23, 2022

Reading Time: 5 minutes

When I speak with people about mold I hear a similar response from many, “I have a clean house. I don’t have mold in my house.”

People often associate a mold problem with a neglected, filthy house or one of those homes from a “hoarder” reality TV show. As any mold inspector will tell you, this is not always the case. In fact, if finding mold was just a matter of finding the big black stuff on walls, mold inspectors would be out of a job. But mold is not that simple, mold can hide, even in a pristinely kept home. 

Mold… a problem for clean homes too.

Mold hides in many places. It can be hidden in a wall cavity, behind your master shower, in your HVAC system, etc. It can be in a number of areas that you would never look.

This past week I was inspecting a home with a large master tub. On the outside, it looked fine, but one look underneath and I saw all the jets and pipes under the tub were covered with mold. All the wood framing was covered in mold. All the sheetrock was covered in mold. Mold can easily hide under a tub because nobody looks underneath their tub. The things that should concern you are mold spores and mycotoxins. They are tiny and you can’t see them with the naked eye. For reference, a human hair is about 100 microns in size. Mold spores which can be coated with mycotoxins are 3 microns and completely imperceptible without a microscope.

So if you keep your home clean, how does mold sneak into these places? Where does it come from? Common places include wall cavities (spce between your walls) and ceiling spaces (empty space above your ceiling) where mold can grow undetected and then enter your home air through small holes or gaps in your walls.

Your wall might have cavities

One common wall cavity issue I see is around electrical wall outlets. If there is a gap in the wall outlet, then the wall air behind that wall will communicate or “talk” with my breathable air. So if there is a mold problem behind the wall, that mold problem is now contaminating with the indoor air. There could be a water intrusion behind that wall like a leak or leftover building materials that were previously contaminated. Even without a significant water leak event, statistically, the air in my attic, wall cavities, or in my crawl space will have about ten times higher mold contaminants than my normal breathable air. I can take my air testing equipment and test that area, but even without doing that testing, I just know that the air behind that wall is naturally a lot higher in mold spores.

One day I was putting in a ventilation system in a woman’s home where I had to cut a six-inch circle in an outside wall. While I was inside her home, I made the cut and started removing the insulation from the hole, and all of a sudden all this dust, dirt, and debris blew in my face, mouth, and into my contact lenses. Yuck. I wondered if I’d punctured a pipe behind this wall, but in fact, all that happened was that the air conditioner came on. It created negative air pressure, or suction, in every cavity of her house. Negative air pressure will bring in things you can see and a whole lot more mold spores and mycotoxins that you can’t see.

Therefore, it is extremely important to seal any cavities in the home that will allow contaminated air to “talk” with your inside air. Sealing your electrical outlets and lights can prevent contaminated air from contaminating your inside air. I’ve created an instructional video on how to seal walls and ceilings where I give examples of sealing outlets and light switches with inexpensive gasket sealers you can get at any hardware store. It also shows how to seal your recessed lighting, which can be a big problem.

The solutions are cheap, easy, and make a big difference. 

Using fog to find areas of contamination

Now that you know how to seal cavities, it’s time to find all the cavities which will require a bit more effort. One way to do this is to run a fog machine, like those in the HavenFog Kits. In short, you put your fogger in an attic or crawl space and allow it to get really foggy. Then you look for leaks in your home by where the fog emerges.

To find cavities in the attic or crawl space use HavenFog and let it run. 

Once after doing this for a client, I decided to do the same thing to my own home. I hopped up in my attic, got my attic real foggy, and turned on my HVAC system. I walked around my house looking at my registers. I’m thinking “I’m a rock star”. No fog is coming out, until I walked into my kitchen. Fog is just pouring out my can lights on the ceiling and my door jam base plate. The fog showed me exactly where my attic air was getting into my kitchen and potentially contaminating my indoor air. I then got some metal duct tape and covered the mounting holes on the can lights. With a $4 tube of silicon, I sealed around the trim of my doorway.

Other common problems… Pipes and ladders.

Another area that is easy to miss is pipes. Pipes come up from the crawl space or come down from the attic and run into the kitchen, bathroom, or laundry room areas where contaminated air can mix with my breathable air. Again, this can be especially problematic with the negative air pressure from an HVAC unit. Radiant heat can push air from one side of the house to another while air from a crawlspace can rise up and come out from pipes as well.

Finally, consider your attic access. Often those fold-down ladders in a hallway or master closet are not well sealed. If you don’t need to access your attic but a few times a year, you can use silicone sealant to go around that entry. Then when you need to get into the attic, cut your seal and get what you need and then reseal it with silicone. It is extra work, but it is amazing how much nasty air your attic will bring into your breathable air environment. 

Fold-down ladders present a problem for indoor air because they are not sealed. 

May our homes be mold-free.

I hope this brief discussion about common air contamination sources (even inside a well maintained and clean home), will motivate you to take some steps to seal up wall and ceiling cavities that are likely to be bringing some pretty nasty stuff into your home. As always, if you are having a hard time tackling your mold issues contact us and we’ll see how we can help.