Mold is an exaggeration for homeowners. Due to the complexity of the biological process, mold is excluded in home inspection contracts. The problem has received so much publicity that many people are wondering what conditions can lead to the growth of mushrooms in the house. First, the problem most often occurs because of a problem with water on the outside, such as a roof leak or uncontrolled water, which has allowed water to stand in the bypass space or basement.
When analyzing homes, professionals usually deal with relative humidity (RH), and this is the percentage of moisture in the air. Air is rated at 100%. It can not retain more moisture, so when installing air on the surface of the condensate. When this happens, we begin to see obvious problems.
The warmer the air, the more moisture it can hold. But when the temperature drops overnight, the cold air is less able to retain moisture. If the house is 70 degrees F and RH is 50%, what happens if the temperature drops to 50 degrees F? The simple answer is: relative humidity rises to 100%, and condensation becomes irrelevant.
Probably the first place that a person sees is excess moisture, condensation, is on the windows, but moisture can also occur on the walls or in the walls. Research and experience show that condensation usually occurs on walls / sheathing, and not so often inside walls or on insulation of internal walls.
People often ask this question: what is the optimum relative humidity for my house? At first it is difficult to answer what you would think. The fast number, at least for my region of the country and provided by the Northwest Clean Air Agency, ranges from 30% to 50% with readings up to 60%, which are usually not the cause of great alarm. It is best to follow the reading in the winter.
The problem is the dew point. Remember that air is regulated when relative humidity is 100%. Well, the dew point is the temperature at which water condenses inside the house. Some people think that the dew point is a low temperature around freezing and that this temperature can never occur inside a house. It's harder than that.
Some practical examples are in order. In the house, if the RH is 40% and the temperature is 69 degrees Fahrenheit, the dew point in the house is 44 degrees - the temperature should drop to 44 degrees before condensation forms. This is a typical RH and temperature based on my research in this northwestern region of the country.
In another example, if the RH is 56% and the temperature is 70 degrees F, this change in the equation leads to a dew point of 53 degrees F. Condensation forms if the house falls to 53 degrees Fahrenheit.
In the last example, let's look at higher rates that may exist inside a house that is wet. With a relative humidity of 77% and a temperature of 73 degrees Fahrenheit, the dew point is 66 degrees F - only 2 degrees under 68 degrees, which many people use as the ideal thermostat setting! If the house drops to 66 degrees, condensation will form inside.
It is obvious that, especially in winter, homeowners need to maintain relative humidity. Where I live, in colder weather, it is more practical to keep a home somewhere above 44 degrees overnight than to keep it above 65 degrees.
This detailed information goes beyond what most people, including inspectors, will constantly participate in. A warning word, while you can get useful information from relative humidity readings, to get enough information, most of the information is needed to determine if a problem exists. This requires some study and analysis. And, some homes that seem to them should have mold growth, but, on the contrary, may be true. Being warned about this information helps to better understand why some homes have wet spots or stains. Excessive humidity caused by high relative humidity can cause damage to leaf rock, wood rot, mold, mildew, rust on metal, shrinkage or expanding wood, reduced heat resistance of insulation, and odors. Often people ask what causes high relative humidity. It is not always easy to say, but some of the usual suspects are showers, baths; Cooking; washing clothes, dishes, floors and walls; breath, sweaty; pets; uncontrolled surface water, wet by-pass spaces and basements.
If you are personally interested in looking at the RH in your home, buy a humidity sensor (hygrometer) from an electronics store or online. You can easily find online, dew point calculators or “psychological charts” that will allow you to determine the dew point from the temperature rand readings of relative humidity.
