Understanding Home Moisture

Home moisture control is a balancing act.

Air that is too damp can cause problems with mold and mildew growth. It causes condensation on windows. It can even lead to rotting wood  in your house. Damp air contains mold spores that are toxic. They can be a health risk.  Children with asthma and people with mold allergies can be especially susceptible.

When home moisture is overly dry  it can cause furniture to crack or sparks to fly when you touch someone. Also a lack of moisture causes uncomfortable,  dry and itchy skin and nasal passages.

What Is Relative Humidity?

home moisture showing a condensationRelative humidity tells us how much moisture is in the air in relation to the amount the air can hold at a given temperature. When air contains all the water vapor it can hold at that specific temperature the relative humidity is 100%. When the moisture is above 100% it will begin to condense .  When air contains 1/4  of the water it can hold at that temperature, the relative humidity is twenty-five per cent.

Cool air can not hold as much moisture as warm air. Think about the humidity on a hot summer day. As a sample of air warms, the relative humidity drops.

What is the right home moisture level?

The best relative humidity for a house is less than fifty to fifty-five percent. Home moisture levels below 50% is good to keep mold from growing in your home. If  in cold temperatures there is condensation on your windows you may need to drop the relative humidity. Try as low as thirty-five percent. Refer to Controlling Household Condensation for more information.

For people with asthma it is advisable to keep bedroom humidity in the 40% range. This is to discourage dust mites that prefer levels of 50% and up. Dust mites make asthma worse.

There are some cases where home moisture problems won’t be solved by dropping the relative humidity. Improperly installed or damaged vapor barriers or can create cold areas in your home. These areas attract condensation. Running a dehumidifier rarely resolves the issue. You may need to call in someone to renovate the problem spots. Be aware that these circumstances can lead to black mold growth.  You may require professional mold removal service.

 Where does moisture in air come from?

Home moisture comes from many sources. Washing dishes or clothes, showering or cleaning floors all use water. Simply breathing releases moisture into the air. Damp outdoor air enters your house every time the door opens. Most houses are equipped to deal with this kind of moisture

On the other hand, when there are  floods or plumbing leaks mold can develop within one or two days. You need to deal with such emergencies immediately.

How to measure your home’s moisture level

You can measure relative humidity with a hygrometer or humidity sensor.  Some  hygrometers are electronic and some are mechanical. Both are easy to use and fairly inexpensive to acquire.

Mold inspectors also use surface or pin moisture meters, also known as mold meters.

Preventing too much home moisture

Easy preventive measures are: drying clothes outdoors and not running a humidifier. Make sure your cloths dryer is venting to the outdoors. Another good investment is to install a fan in your bathroom.  It will vent the moist air out of the house from bathing and showering moisture.

A heat recovery ventilator works well. Fresh air intakes combined with an exhaust fan helps ventilate  and decreases relative humidity. Use an air conditioner that dehumidifies incoming air instead of just making it cooler. These air conditioners have a high rating for latent heat rather than a rating for sensible heat.

Be aware of how the stack effect of air pressure can be used to advantage or create condensation leading to mold infestations.

A dehumidifier is an effective way of preventing moisture problems.

Be sure to read How to Control Humidity and What is Moisture?  or Reduce humidity, moisture and mold for additional information about limiting home moisture.