Is Humidity a Problem in Your Home?

It is common knowledge that too much humidity can cause extensive and expensive damage to your home.  Humidity is invisible as the air carries it.  It would be helpful if we could see this harmful humidity. There is one reliable visible warning that there is damaging humidity in your home.  It is the build-up of water vapor on your windows.  This condenses to form fog or frost on your window panes.  Here we will attempt to help you understand and come to grips with the humidity and the problems it causes.

IS IT A PROBLEM OR SYMPTOM?            

It is actually both a problem and a symptom.  A little amount of fog or frost on the lower parts of your windows is nothing to worry about.  If it blocks the entire window you have a problem.  This is a symptom of moisture damage that is occurring throughout your home.

Homes are built tighter today to make them more energy efficient, but the price that is paid for this is a dramatic increase in humidity.  The tighter construction helps hold the humidity in.  The tighter construction of a home to make it more energy efficient is a good thing.  The increase in humidity is a problem that can be solved by following a few simple steps, which we will go into in this article.  

VAPOR PRESSURE:

The outside air is typically dryer than the air inside the home.  Therefore, the humid air tries to flow towards and mix with the outside drier air.  It is called vapor pressure.  Vapor Pressure can go upstream to air flow as it forces moisture through wood, plaster, brick, cement and most of the other materials we use to build our homes.  You can see this happening as you see blisters form under your paint on the exterior of your home. This is from the vapor pressure forcing the moisture out through your siding.

HUMIDITY TRAP:

We use more moisture trapping materials to build and decorate our homes today.  The increase in the glass, polyurethane, vinyl wallpaper, vinyl floor coverings, etc. are all traps for moisture.  Add to it vapor-seal insulation and you now have moisture trapped inside.  The results are condensation and fogging.  You can see how this works in your own bathroom when you take a hot shower or bath.  Your mirror and window will fog over.  One other added source of trapped humidity is a house without a basement.

ELEVATED WATER-VAPOR:

There are many changes in the modern households that increase the humidity problem.  Today, we do more washing, take more baths and showers, and have more appliances and furnaces.  There is less dry heat such as fireplaces and wood stoves.  A family of four can increase the humidity level by 18 gallons or 150 pounds each week.  How do we do that?  Simple daily activities such as cooking, washing, laundry and the human bodies themselves all add that moisture.

SAFE HUMIDITY LEVELS:

There is a certain amount of humidity needed to remain in a healthy environment in our homes.  A little fog or moisture on the bottom of your windows in the colder months is normal and indicates an acceptable level of humidity.  You don't want so much that it runs down the window frames or down onto your walls marring your paint or wallpaper.

A humidity gauge called a psychrometer is a very useful item to have in your home and comes in many decorative styles.  Below, is a table showing the acceptable levels for a home heated to 70° F.  The higher the indoor temperature, the lower the humidity should be.

 

Outside Air Temperature	Indoor Relative Humidity
-20°F or below -20°F to -10 -10°F to 0     0°F to 10   10°F to 20   20°F to 40	not over 15% not over 20% not over 25% not over 30% not over 35% not over 40%

 

HOW DO WE REDUCE HUMIDITY?

1.      Shut off all humidifier units. This includes the furnace humidifier unit also.

2.      Air out the house on a daily basis. Air out the kitchen, laundry room, and bathroom while in use.

3.      Use your exhaust fans often and for a longer period of time.

4.      Open the fireplace damper

5.      Have properly sized attic vents and louvers and keep them open.

6.      Make sure dryer vents and all gas burners are vented to the outside.

 

PERSISTENT PROBLEM HUMIDITY?

Windows do not cause humidity problems.  Humidity levels cause the moisture problems.  The reasons for window condensation and humidity can be complicated.  You may need an expert to help you solve the problem if the steps above do not help.  Start by calling your furnace repairman to install an outside air vent for your furnace.  Whatever the humidity problem is, do not let it go unchecked.