Heritage Restoration, Inc.

Mold Issues #1

Over the last few years 2 sides of our house has had a green mold problem that seems to get worse every year.

One side is where we put in central air with heat pumps in 2009, the north side, no trees close to the building. Once or twice every year, I clean what I can reach, with bleach and tsp, which I last did in the fall and the mold has come back again

The other side, (east) which does have tall bushes close to the house, but I keep them trimmed about 2 feet from the house, was also cleaned in the fall and the green mold has come back again.

Its only over the last 3 years that this has happened

The house is painted in solid stain, maybe about 7 years ago

Please help


Many people share your concern, trying to fight nature and the effects. The conditions that make mold thrive are always a little different, so let’s first look at mold and treating it, then we can consider the building, its siting, and how to resolve it long-term.

Molds are all around us. There is no specific amount that defines either safe or unsafe mold exposure, you just know if it is too much by seeing excessive amounts, or your body reacts to it. Mold concentrations outdoors vary greatly with respect to time of year, species, location, and amount. Exposure to airborne mold outdoors, where levels often exceed thousands of spores per cubic meter, is considered safe, it’s just a matter of how feel. Indoors is a different issue altogether. Mold thrives on organic materials, playing a key role in breaking down leaves, wood, and other plant debris. Without mold, we would be buried in plant material. Mold makes tiny spores to reproduce, and the wind picks them up and they float until they land on something. When mold spores land on a damp spot with organic material, they begin to grow and digest.

Mold needs food and water, and houses are great suppliers of both. But how do you control mold on a house’s exterior?
• Remove trees and shrubs that are closer than two or three feet from the house.
• Be sure gutters and downspouts are functioning.
• Maintain exterior finishes, or apply a protective coating over existing finishes. Anti-microbial additives in finishes can fade over time, some faster than others.
• The smoother the siding or surface of the building material, the less organic material will latch on creating the right conditions for mold growth.
• Complete building diagnostics to determine if your building fosters mold growth in other ways. Indoor conditions that increase humidity can cause mold problems inside and outside the house. Moisture wants to go to the warmer, dryer places. Depending on the time of year, moisture is migrating in and out of your walls. Moisture from a house’s INTERIOR effects outside moisture levels on and in wood siding. Understanding the building’s dynamic, and considering changed over the years, are essential to knowing why mold can grow while also preventing it from coming back with the same vigor.

Cleaning is a great step, but it is not a long-term solution. The problem is airborne, so changing conditions is the best long-term solution. Whatever product or cleaning technique you use, first complete a test patch to make sure it works; it is much cheaper than testing on a whole house. There are products that treat mold, and other that clean and provide a protective coating. These products are chemicals and are more than using just using bleach. Bleach is fine for killing mold, although it does not stop it from coming back. Additives in finishes are best, since they can prevent the growth of mold way beyond application.

Outdoor cleaners and pre-paint mildew removers are formulated to kill mold and mildew, remove dirt and stains on most exterior painted or non-porous surfaces, and they do not require scrubbing. They contain mildew ides, bleach activators and detergents. They will not damage painted surfaces and some may be applied near plants and shrubs. Some contain Acetic Acid and Sodium O-Phenylphenate, which are toxic to fish, carcinogens and can mess with your skin. Some are mixed with bleach, so be sure to wear gloves, goggles and other prescribed personal protective gear.

There are also products meant to clean exterior surfaces containing mold, mildew, algae, and surface dirt, and have a protective film to inhibit regrowth of mildew and algae. While it sounds great, it will not protect the surface forever, just buy more time between cleanings.

Curiosity did get the best of me, so I talked to Kit and found out the following:
• The problem has gotten worse over the past 3 years.
• The house has shingle siding.
• The house sits on about 1 acre of woods, mostly pines. There is only one spot with trees about 2 feet from the house, with the canopy overhanging a bit.
• There is a pond a few hundred yards away.
• Insulation was blown into the walls a few years ago.
• Central air was put in about 3 years ago. It smells for about a week after the air conditioning turns on for the season.
• The mold is the worst above the condensers outside.
• The house was built in 1975.

This is where the problem becomes a bit more complicated. More next column.

Leave a Reply