Mold, Indoor Air Quality, and Your Health


If your home isn’t ventilated well, it can set up a veritable breeding ground for mold, leading to poor indoor air quality that can affect the health of your household.

Mold is a key factor in breaking down organic matter such as fallen leaves and dead trees. That’s good for outdoors, but not your house.

Molds reproduce via tiny, invisible ‘spores’ that float in the air. But for these spores to ‘bloom’, warm, moist conditions are required: an average temperature above 70°F and at least 50% to  70% Relative Humidity (RH) or higher.

That’s okay because mold is not usually a problem until it is grown indoors. The only way that mold grows indoors is if there’s a moisture problem. The best way to control mold growth inside the home is to control moisture.

Many types of mold, all grow with water or moisture

Moisture can be generated in your home by many sources. Physical cracks, holes and other penetrations can cause rain, surface runoff to leak into roofs and walls, while cracks in foundations can cause groundwater to seep through walls and basement floors. Daily activities such as showering, laundry, and cooking, when combined with poor or inadequate ventilation, can all be significant moisture sources. Unvented space heaters also add quite a bit of water to the interior of your home and can boost mold growth in many cases.

There are also a number of invisible-to-you sources that can factor into indoor air quality issues and mold growth. One of the biggest of these air leakage. If you live above a moldy basement or crawlspace, chances are, the air quality in your home’s living spaces will be affected. Likewise, duct leakage can bring a fair amount of poor quality air into the home and should always be inspected when air quality issues are at play.

Any combination of these factors can cause an overload of moisture in your home on a seasonal or ongoing basis. In a nutshell, the air in your home can hold a certain amount of moisture, depending on its temperature (and the temperature of the air outside). The lower the air temperature, the less moisture can be held by the air. This explains why moisture condenses onto cold surfaces like windows in the winter.

While you can wipe up condensed moisture on windowsills and other surfaces, what you can’t do is see or clean up moisture in hidden areas. When moisture condenses and temperature conditions are right, you can get mold growth when spores land on the wet or damp area and begin to grow. Reducing the relative humidity of the air in the home is the number one way to minimize condensation and possible wet, damp surfaces inside the house.

Mold in houses causes health problems for people

All molds produce allergens and irritants, and some molds also produce potentially toxic substances called mycotoxins. Outdoors, this is rarely an issue. However, in an enclosed space like a house, molds are a common cause of health problems. Immediate or delayed allergic reactions can be triggered by touching or breathing in mold or mold spores. These reactions include:

  • Sneezing
  • A runny Nose
  • Red Eyes
  • Skin Rash
  • Mold can also trigger asthma attacks or other respiratory problems.

Moisture problems and the resulting mold growth reduce the quality of the indoor environment, making your home less healthy to live in.

Ventilation Solves Mold Problems and Improves IAQ

The first step in minimizing or eliminating mold problems is to fix any and all water leaks, and clean up the visible mold growth — if you don’t fix the water problem, the mold problem will not go away. If you can get some air sealing work done, then you can reduce the amount of air exchange between inside and outside. It’s impossible to get rid of all the mold and mold spores in your house, but that’s okay, as molds will not grow if moisture is not present. Controlling moisture is the key to preventing mold growth.

In order to fight bad air quality, it’s important that you get to know why ventilation is so important in treating moldy homes.

Adding or improving mechanical ventilation is the best solution to continually avoid moisture problems and mold growth. Your house should stay within the range of 40 to 60% RH year round. Getting rid of moist, stale air and replacing it with fresh filtered air keeps the indoor environment from hitting the conditions required for mold growth. In addition, the air movement provided by ventilation helps to reduce the rate of condensation on windows and other cold surfaces.

Whole-house, balanced ventilation systems like those designed and built by Zehnder America are designed to eliminate excess moisture in the air. They work by providing a continuous, low-flow, energy conserving, mold preventing the rate of fresh filtered air while pulling moist air out. Intermittent strong sources of moisture from bathrooms, kitchens and laundry rooms get cleared at higher ventilation rates, so there’s no chance of the moisture to either settle in the ‘wet’ room or to spread throughout the house. Improve the indoor air quality in your home now.

Even if there is not a known active mold problem, installing adequate ventilation such as a Zehnder ComfoAir System can help to keep mold concentrations low and indoor air quality high. Zehnder offers free system design services and will happily be with you through every step of the process! Request a System Quote today.