Energy Adviser: Humidity plays key role in mold problems

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Energy Adviser: Humidity plays key role in mold problems

The Columbian - Vancouver,WA

Sunday, October 8, 2006

BRUCE CARTER for The Columbian Advertisement

http://www.columbian.com/lifeHome/lifeHomeNews/10082006news65673.cfm

My wife and I set our thermostat back at night to keep the house

cooler for sleeping as well as to lower our heating bill. In January

I noticed that a fine layer of white mildew started coating the

shoes and clothes in our bedroom closet. We cracked the window at

night to add a little ventilation hoping that it would cure our

mildew problem, but it didn't seem to help. I am worried that the

same problem will come back this winter. What causes it and how do

we keep it from happening?

Mold is a living entity. As such, it requires oxygen, a food source

and moisture to survive. Although there is no practical way to

eliminate mold spores from your home, the best way to stop mold from

growing is to identify and take away the moisture allowing it to

thrive.

By far one of the most common moisture sources leading to mold

growth is a water leak. Leaky plumbing inside the wall or in the

crawlspace can go unnoticed long enough to establish a mold colony.

Standing water in the crawlspace often leads to mold problems in the

house above. Once established, mold no longer needs liquid moisture,

but can thrive with high moisture content in the air. Fix plumbing

or outside water leaks and make sure basements and crawlspaces have

no standing water.

High concentrations of water vapor -- humidity -- can also lead to

mold growth. High humidity levels can be much harder to understand

and control.

Saturation point

" Relative humidity " describes the amount of moisture vapor in air at

a specific temperature. The closer the air gets to saturation -- the

point where the air can no longer hold the moisture as a vapor --

the higher the relative humidity.

Warm air can hold more water vapor than cool air. As air cools, its

relative humidity rises. As an example, 70-degree air at 50-percent

relative humidity becomes saturated air when the temperature drops

to 48 degrees. This is important because mold can thrive when

relative humidity rises above 50 percent.

When you lower the temperature in your home at night, you decrease

the air's ability to hold moisture and its relative humidity rises.

As you and your wife breathe during the night, you add vapor to the

air. This, coupled with cooler temperatures in the room, causes the

humidity in the room to rise. When the air temperature reaches 60

degrees, the relative humidity is about 70 percent, which is more

than enough to support mildew growth.

So how do you control this problem? First, look for a source of

liquid moisture in or under the bedroom. Make sure the crawlspace

has plastic sheeting covering all the dirt under the home. If there

is standing water in the crawlspace, pump it out.

If there is no source of liquid moisture, keep the relative humidity

in the bedroom below 50 percent. Purchase an inexpensive hygrometer,

an instrument that measures relative humidity, to help track it in

your bedroom. Hygrometers are available at many hardware and home

improvement stores. To control relative humidity, keep the bedroom a

little warmer at night. Cracking a window will also lower relative

humidity by bringing in cooler, drier outside air. If necessary,

purchase a small, portable dehumidifier for the bedroom to control

humidity.

Public Utilities is holding a free workshop on mold and other

moisture-related problems Tuesday at 7 p.m. at the utility's

community room located at 1200 Fort Vancouver Way.

Bruce is an energy specialist for Public Utilities.

Send questions to energyadviser@... or to Energy Adviser in

care of Public Utilities, P.O. Box 8900, Vancouver, WA 98668.

A panel of local energy-efficiency and energy-product experts will

review your questions. Past topics are at www.clarkpud.com.