How to Cure Window Condensation in Your Home

Causes and Cures for Window Condensation

Each winter sees more and more homeowners vitally interested in solving window condensation. Window condensation is not a happy interest because of bad experiences, which range from irritating to downright expensive.

It may strike you as odd, but the growing condensation problems of the nation are caused by progress. If you have trouble with window condensation, it's probably because you live in a "tight" modern home that you can heat for a fraction of the money it took to heat the house your parents lived in—a home that's cleaner and more comfortable besides! Your condensation problems also result from use of labor saving appliances that make life easier than it used to be.

This article explains the moisture problem of the "tight" home. It offers suggestions for curing condensation problems in existing homes and provides additional suggestions for you who are planning a home. You unquestionably will build a "tight" home, and there are more things you can do to prevent excessive moisture when you build than can be done in a home where the problem already exists.

What Causes "Trouble" Condensation?

A little fog on the lower corners of your windows now and then probably doesn't bother you. By the time you've thought about it a second time it has usually gone away. But we are talking about excessive condensation. Condensation that blocks whole windows with fog or frost. Water that runs off windows to stain woodwork, or in serious cases even damage the wallpaper or plaster. If you have this kind of condensation on your windows, you have good reasons to be concerned and good reason to act.

Don't worry so much about the windows where you can see the effect of excess humidity. You should worry more about what excess moisture may be doing elsewhere in your home. It may be freezing in the insulation in your attic where it will melt and damage your plaster exactly like a roof leak when warm weather comes. Or it may be forcing its way out through siding to form blisters under your exterior paint. That means the most expensive kind of a paint job. It's easy in such cases to blame the paint, or the insulation, or the windows, but it's wrong to blame them. The real villain is invisible. It's water vapor. The best, and usually the only way, to prevent this trouble is to get rid of excess water vapor. Once you've equipped your windows with good storm windows, there isn't very much more you can do to the windows to lick condensation.

What Is Humidity?

Humidity, water vapor, moisture, and steam are all the same in that they are each a form of water. Humidity is an invisible gas. It is present in varying quantities in nearly all air. This moisture in wet air tries to flow toward drier air and mix with it. Scientists describe this force as "vapor pressure." It is often a very powerful force indeed. It can act independently of the flow of the air which holds the moisture. Vapor pressure can force moisture easily through wood, plaster, brick, and cement—right through most of the materials we use to build our homes. That is exactly what happens when moisture seeks to escape from the humid air usually found inside your home to the drier winter air outside.

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Passyfier Dehumidifier Core Wall Vent Kits (High Rise)

The Passyfier Dehumidifier CoreWall Vent Kits also come in a High Rise version. These are to be used in situations where there are more than two levels high i.e a block of flats, apartments and town houses.

Instead of paying out a lot of money for scaffolding to fit from outside in, these Passyfier core wall vents can be fitted from the inside of the property. This is possible because the rubber seal gasket seals the hole from the outside.

The Passyfier Dehumidifier High Rise Core Wall Vent Kit comes in two different sizes. The 4” core can treat up to 5m² of floor area and can transmit 0.75 litres of water vapour transmission in 24 hours. Whereas the 6” core can treat up to 10m² of floor area and can transmit 1.4 litres of water vapour transmission.

Passyfier Dehumidifier Vent

Passyfier Dehumidifier Vents are used as an aid to help with the control of condensation problems. These vents are used in rooms such as bedrooms, living rooms and dining rooms. For your kitchen and bathrooms extractor fans would be needed as they can extract more water vapour in a shorter period of time than a Passyfier Dehumidifier Vent can.

How Passyfier Dehumidifier Vent Works

Imagine you have a clear plastic bag and you blow into it, you will be able to see water vapour from your breath, this vapour needs to go somewhere. If you then pop the bag the water vapour then can escape. This is how the Passyfier Dehumidifier Vents works it acts like an exhaust. Not only does it help draw the water vapour out of your habitable rooms but also helps with some of the draught problems unlike other vents, so there will be no more need to block up your airbrick vents when you replace them with the Passyfier Dehumidifier Vents.

The Passyfier is a non mechanical Dehumidifier Vent, so there are no running costs to worry about. There are no parts that need to be cleaned or changed.

There are two versions of the Passyfier Dehumidifier Vent. You can get it in a sleeved version or core version. The Passyfier Sleeved Wall Vent Kit is the most popular as it can do a bigger room size and can transmit higher water vapour transmission than the core versions. However the core versions are quicker and easier to fit.

The Passyfier Sleeved Wall Vent Kit also comes in a range of different airbrick colours and a choice of internal grille options. Extension sleeves are also available for those thick walls.

The Reason Why Condensation Forms

Condensation is the water produced when warm moist air or steam meets a cold surface such as windows, walls or floors.  It is sometimes so bad that householders believe their windows leak or that their house is structurally damp.

Condensation is often a problem in older non-thermally efficient houses or newer houses where doors and windows are more draught proof than in older properties or where there is central heating installed and there are no or fewer chimneys.

Condensation can cause mould growth on walls,ceilings and floors and can damage clothes and furnishings.  Controlling it is a matter of reducing sources of water vapour to a minimum and finding the right balance between heating and ventilation in your particular home etc

Here are some ways to help you control condensation

MAIN CAUSES OF CONDENSATION

• Boiling Kettles and saucepans.
• Washing and drying clothes.
• Bathing and showering.
• Using paraffin and flueless gas heaters.
• An over occupied property.

 TO CONTROL CONDENSATION

• When washing and drying clothes or cooking, keep kitchen door shut and open window.
• When bathing and after bathing, keep bathroom door shut and window open
• Air your house every day.  Every window in the house should be open for at least 10 – 15 minutes each day except in the coldest weather.
• Have bedroom windows slightly open at night,(ie on the security night latch lock position) even the breath of a sleeping person contains a lot of water vapour.
• Take advantage of dry, sunny days to give your house a good airing; and don’t forget the cupboards
• Use extractor fans where fitted.
• NEVER block up existing air bricks, flues or ventilators.  THIS COULD BE DANGEROUS. As they may be providing Air Combustion for a heating appliance/s. Ask a qualified Gas/Oil/ Solid Fuel/Paraffin/etc. engineer if they can be removed!
• If you use paraffin or flueless gas heaters, keep the windows open a little (every gallon of paraffin burned produces 1¼ (6 litres) gallons of water!)
• Keep your house warm (consistent with fuel economy requirements) even if you are out during the day.

PRINCIPLES OF CONDENSATION

Warm air can hold more moisture than cold air.  If air in a building acquires additional moisture this increased moisture content will not be apparent in places where the air is also warmed.  But if this moist air comes into contact with colder air, or with a cold surface, then air is likely to be cooled to its dew point temperature and sample of air is likely to be saturated, and the excess water vapour condenses to a liquid.

This effect could also be achieved by the same body of air without the addition of moisture, being allowed to cool down until it reaches its saturation point  (dew point).

TECHNICAL BACKGROUND

Condensation in buildings is a form of dampness caused by excess water vapour in the air.  Among the effects of condensation are misting of windows, beads of water on non-absorbent materials and mould growth.

As a general principal it can be stated that:

        Condensation occurs whenever moisture laden air meets

 surfaces that are at or below the dew point of that air.

The two types of condensation can be classified into two main types:

 1.     Surface Condensation;

 2.     Interstitial Condensation.

Surface Condensation 

Surface condensation occurs on the surfaces of walls, windows, ceilings and floors.  The condensation appears as a film of moisture or beads of water on a surface and is most obvious on the harder, more impervious surfaces such as ceramic wall tiles.  An absorbent surface may not show condensation at first, although persistent condensation will eventually cause dampness.

Interstitial Condensation

Interstitial Condensation occurs within the construction of the building. Most building materials are, to some extent, permeable to water vapour (that is, they allow the passage of air containing moisture).  If this air cools as it passes through the structure then, at the dew point temperature, condensation will begin to occur inside the structure and can damage important structural materials, such as steelwork.

What is Condensation

What is condensation?
Condensation is the accumulation of water vapor changing to liquid water onto a surface. When the interior temperature is warmer than the window surface, there is a chance that condensation will form. As the outside temperature decreases, the inside of the window surface will drop, causing the interior window surface to be between the exterior temperature and the interior temperature.  Since it is not possible to control the exterior, the interior conditions must be controlled in order to prevent condensation.

What is dew point?
The dew point is the temperature at which water vapor in the air will condense into liquid water. The dew point temperature will change depending on the inside temperature and relative humidity. When any surface temperature falls below the dew point, water will condense on the surface, such as a cold can of soda or a glass window.

What is relative humidity?
Relative humidity is the ratio between how much water vapor is in the air and the maximum amount of water that can be held in the air. The maximum amount of water vapor that air can hold varies with the temperature of the air. As the temperature of the air increases, it is able to retain more water vapor. When the interior air comes in contact with the colder window surface the air temperature drops and it is unable to hold as much water, this causes the excess water to accumulate onto the window surface.

How do I prevent condensation?
In order to prevent condensation, humidity in the room must be controlled. As the exterior temperature is colder, the humidity inside must be lowered as well to prevent condensation.   To lower condensation, dehumidifiers can be used and are one of the most effective ways to control humidity. Environmental conditions that lead to condensation formation are often temporary. These causes include: extreme cold outside temperatures, cooking, showering, and clothes drying. If the formation of condensation is more than a temporary condition, an HVAC expert should be consulted to evaluate the relative humidity within the room and/or building

What should my relative humidity be to prevent condensation?
Based on Engineering Studies at 70ºF conducted at the University of Minnesota Laboratories, the American Architectural Manufactures Association (AAMA) suggests that humidity levels not exceed the values referenced in the below table to prevent condensation. Outside Air Temperature Inside Relative Humidity

-20ºF or below Not Over 15%
-20ºF to -10ºF Not Over 20%
-10ºF to 0ºF Not Over 25%
0ºF to 40º Not Over 30%
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