EPA guidelines to Mold Prevention and Treatment

Moisture problems and their solutions differ from one climate to another. The Northeast is cold and wet; the Southwest is hot and dry; the South is hot and wet; and the Western Mountain states are cold and dry. All of these regions can have moisture problems. For example, evaporative coolers used in the Southwest can encourage the growth of biological pollutants.

In other hot regions, the use of air conditioners which cool the air too quickly may prevent the air conditioners from running long enough to remove excess moisture from the air.

The types of construction and weatherization for the different climates can lead to different problems and solutions. Take each into consideration.

As the temperature goes down, the air is able to hold less moisture, therefore, in cold weather, moisture condenses on cold surfaces (for example, drops of water form on the inside of a window). This moisture can encourage biological pollutants to grow.

Environmental Protection Agency (EPA) Guidance

Moisture Control

Water in your home can come from many sources.
Water can enter your home by leaking or by seeping through basement floors.
Showers or even cooking can add moisture to the air in your home.
The amount of moisture that the air in your home can hold depends on the temperature of the air.

Moisture On Windows

Your humidistat is set too high if excessive moisture collects on windows and other cold surfaces.

Excess humidity for a prolonged time can damage walls especially when outdoor air temperatures are very low.

Excess moisture condenses on window glass because the glass is cold.

Other sources of excess moisture besides overuse of a humidifier may be long showers, running water for other uses, boiling or steaming in cooking, plants, and drying clothes indoors.

A tight, energy efficient house holds more moisture inside;

you may need to run a kitchen or bath ventilating fan sometimes, or open a window briefly.

Storm windows and caulking around windows keep the interior glass warmer and reduce condensation of moisture there.

Humidifiers are not recommended for use in buildings without proper vapor barriers because of potential damage from moisture buildup.

Consult a building contractor to determine the adequacy of the vapor barrier in your house.

Use a humidity indicator to measure the relative humidity in your house.

The American Society of Heating and Air Conditioning Engineers (ASHRAE) recommends these maximum indoor humidity levels.

Outdoor Recommended Indoor Temperature Relative Humidity

Source:  Anne Field, Extension Specialist, Emeritus, with reference from the Association for Home Appliance Manufacturers (www.aham.org).

In the second case, assume that the RH is 50% and the temperature is 70oF in the middle of the room. 

The higher RH at that temperature indicates that the water vapor pressure is high and there is a relatively large amount of moisture in the air. 

The high surface RH is probably due to air that is "too moist." 

Humidity is the dominating factor, and control strategies should involve decreasing the moisture content of the indoor air.

Key Facts About Hurricane Recovery

www.bt.cdc.gov/hurricanes/index.asp                        
University of Minnesota, Department of Environmental Health & Safety -
www.dehs.umn.edu/iaq/flood.html            
"Managing Water Infiltration Into Buildings."  A Systematized Approach for Remediating Water Problems in Buildings due to Floods, Roof Leaks, Potable Water Leaks, Sewage Backup, Steam Leaks and Groundwater Infiltration.  Questions and comments may be directed to:  Neil Carlson, M.S., CIH, Department of Environmental Health & Safety, University of Minnesota, or Arif Quraishi, M.E., Vice President, Special Projects, Indoor Environments Division, Institute for Environmental Assessment, Inc.