Mold: Room by Room
It is possible for mold to grow anywhere in the home. All that the ever present mold spores need to live is a little water and a material to grow on. Once it has these two things, mold is off and running and can grow in as little as 24 hours. Because moisture is such a key component, the most common spaces in a home where you might find mold are the basement, kitchen, attic, bathroom, HVAC, laundry room, and crawl spaces.
Before getting into what makes each of those rooms particularly vulnerable, here is more information on common causes for excess moisture indoors: unsuitable temperatures and relative humidity levels.
The temperature that is conducive for most molds to grow in is between 65 and 75 degrees fahrenheit. Unfortunately, this is also the temperature range that most people are comfortable living in. Despite this range, there are still types of mold that can grow in extreme cold and extreme heat so sacrificing comfort in an attempt to prevent mold growth in your home is not recommended.
Relative humidity, the ratio of moisture present in the air to the maximum amount of moisture the air can hold, can be a key indicator of excess moisture indoors and a potential source of mold growth. Controlling the relative humidity in your home is vital to controlling mold growth. The recommended level of relative humidity in a room to limit mold growth is 60%. However, simply maintaining this level in the air is not enough since mold does not grow on air, it grows on surfaces. Cold spots or moisture pockets can alter the relative humidity near surfaces where mold can begin to grow.
Water vapor can enter into the home and increase its moisture level through human breath, steamy showers, humidifiers, vents, cracks in doors and windows, etc. As the temperature lowers, air is able to hold less moisture. Therefore, when the temperature drops, the relative humidity of that air goes up. This increases the possibility of condensation forming. Condensation forms when a unit of air contains all of the water vapor it can hold meaning the relative humidity is at 100%.
The relative humidity and the temperature can be inconsistent throughout the same room. If a surface in a room is really cold or one area of the room is cooler than another, then those spots will have the highest relative humidity. This helps explain why mold will sometimes grow in one specific spot. It is likely those areas are cooler, which can be caused by many things including an appliance, cracks in the walls, or a break in insulation. Moisture meters are good tools in helping detect hidden wet areas in a home.
Mold in Basement
Mold found in the basement is very common. Basements are typically dark, damp, and with little to no ventilation. Moisture can find its way in through cracks in the walls or windows and stick around for a long time. Flooded basements can cause water damage and can be a breeding ground for mold growth.
In addition to the walls and wet carpeting, other areas to inspect for excess moisture and mold growth in the basement include a sump pump and its discharge area, plumbing pipes and lines, drains, and vents. Also check the collection plate of any dehumidifier. This could be dripping onto carpet and causing a problem.
If you come across flooding in a basement, do not enter the water and do not inspect it alone. The water could have passed over electrical outlets and have an electric current running through it. This is extremely dangerous and could electrocute anyone who touches the water. If you can get to the circuit breaker safely, cut the power to the basement before moving forward. Since this situation is so unsafe, it is best to call in professionals to solve this problem.