Isaac Savage looks at Spring’s unwelcome house guest.

Mold is good…except when it’s growing inside your house. Without mold, decomposition would not occur, cheese would be boring, and the majority of houses in western North Carolina would be missing the musty smell that wafts up from the ductwork every time the air is turned on.
Mold is what makes nature’s cycle complete. The role of mold is to break down the energy in plants/cellulose so that it can return to the earth, beginning its cycle all over again.

Our society has decided that it makes good sense to build our houses out of trees. We frame them with sticks of wood, sheath them with plywood and OSB (shredded wood mixed with glue and heat), and finish off the inside with sheetrock that is sandwiched between paper. Even though we live in houses made of mold food, this fodder is only appetizing when moisture levels are out of balance. Therefore, it becomes very important that we keep them dry.
There are three main sources of moisture introduction in a house: plumbing leaks, water from the outside and moisture produced inside the home.

Plumbing leaks are typically a result of freezing.
The only way a pipe can freeze in a house is if it’s located in an exterior wall cavity that is poorly insulated or in a cavity that is connected to outdoor air via breaks in the air-barrier. When planning the location of plumbing, consider the temperature of the cavity where the pipes are located. Interior walls and well-sealed floor cavities are the best options. When positioning water heaters or air-handlers on upper levels, include drain pans beneath them to prevent damage if a leak occurs.

Outside moisture comes from the sky, from the ground and from the air.
Water from the sky should go exactly where you want it to go—away from your house. Leaky roofs and flashing details, negative slopes around the house (land sloping toward your house), missing drainage planes between the sheathing and the siding, and non-functioning gutters are typical “sky water” problems.

Water from the ground should also be managed by design. The lack of vapor control systems in the crawlspace and poor (or non-existent) exterior foundation drainage systems are common ground water intrusion problems.

The most mysterious of the three is moisture from the air—vapor. Vapor gets into the home via air leakage or by diffusing through each material that your building envelope (walls/roof/floor) is composed of. Air leakage transports about 100 times more moisture from outside to inside than the natural diffusion of vapor through the materials in the wall. As such, air leakage can also be a source of moisture that needs to be addressed.

Outside air that leaks into your home through the building envelope carries moisture into these cavities. If these cavities contain wood, darkness and the right temperature range, you have perfect conditions for mold growth. In the summertime, outside vapor tends to move into the house (from high levels to low levels). In the wintertime, the opposite is true. So, the likelihood of mold growth is pretty high when outdoor air can leak into the wall cavities and condense on the back of a cold piece of sheetrock (air-conditioned house) that is lined with paper. This is also a problem if there is a layer of plastic between the sheetrock and the studs. The condensation will then drip down the plastic and settle at the bottom of the wall. The same can be said in the winter, only the cold sheathing is the outer surface of the house. The only way to control this air-transported vapor is to seal the holes in your walls, which, like most things, is easier to do while the house is being built.

To battle outdoor moisture, the house should be as air-tight as possible and be designed to shed water. There are many materials and systems that play a part in the control of moisture. For example, there are exotic materials that are simple to install, while there are also simple materials that require more careful installation. Either direction will work as long as the building envelope is functioning as a system. Investing more energy and money in controlling moisture within the building envelope will be well worth the effort in the long run.

Moisture produced inside the house should be removed with proper use of bathroom and kitchen exhaust fans.
It is imperative that these ducts take the exhausted air all the way to the outside, not just into the attic. It is also important that the ductwork on these fans be as short as possible with very few bends. If you cannot avoid a long duct run, get a larger fan or install a booster fan to compensate for the added static pressure.

Oversized air conditioners (A/C) are also quite common and can create high moisture levels inside the home. First, understand that the role of an A/C is to cool and dehumidify. When an A/C unit is too large, it satisfies the temperature demand of the thermostat before it has the chance to remove enough moisture to make the house comfortable (this requires longer run times). All you’re left with in this scenario is cool/sticky air, high moisture levels, and lots of cold surfaces. Remember, bigger is not always better.

What size is the right size? A “Manual-J” calculation can be done to determine the proper sized machinery for your specific house. This calculation is not done on paper or in one’s head and can only be accurately generated by using a sophisticated computer software program which takes many different variables into account, all of which are specific to your house. This report not only tells you how big the overall system should be, but also how much air to inject into each room of the house for optimum comfort.

No one wants a rotting house that stinks of mold. A true sign of a quality house is one that handles moisture properly. Whether you’re trying to improve your current property or building a new home, focusing on moisture control should be a top priority for your health
and your wallet.

WHAT IS MOLD?
Mold is a fungus that can grow on and decompose any number of objects. There are various types of mold, some of these can emit toxins that can be potentially harmful to humans and animals. Toxic mold poses the biggest threat to those individuals with weak immune systems such as babies or the elderly.

WHERE CAN MOLDS BE FOUND?
Molds are usually found wherever there is moisture, such as under a leaky pipe. Molds may grow wherever there is water, oxygen and something they can stick to and feed on. Outdoors, they are found on rotting materials such as logs, branches, plants and leaves, especially in dark, moist areas. Molds may grow indoors and into our homes in dark, damp areas such as closets, basements, and under kitchen or bathroom sinks. While mold grows in moist areas, it can still exist once the water has dried up. These can all be seen and removed while the worst is when mold creeps into wall cavities and underneath the flooring of a home, where they cannot be seen.

WHAT ARE THE POTENTIAL HEALTH EFFECTS?
Molds and mold spores produce mycotoxins that can cause a number of health problems. Mycotoxins may cause diseases related to indoor airborne exposure to molds. Skin is another potential route of exposure to mycotoxins, and toxins of several fungi can cause cases of severe dermatosis. In view of the serious nature of the toxic effects reported for mycotoxins, exposure to mycotoxin-producing agents should be minimized.

PEOPLE SENSITIVE TO MOLD MAY EXPERIENCE…

Nasal stuffiness
Cough
Eye irritation
Wheezing
Skin irritation
Fever
Chills
Muscular aches
Respiratory problems:
Asthma
Shortness of breath and other Respiratory problems
Headache
Confusion
Depression
Fatigue
Irritability
Sleep Disorders
Cancer
Death

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