Why Does Condensation Form on Aluminum Window and Door Glass? Solutions Inside!"

In winter, aluminum windows and doors may encounter a problem - the inside of the windows is covered with water droplets. In professional terms, this is called: condensation on windows and doors.

Condensation on aluminum doors and windows refers to the accumulation of dew or water vapor on the indoor surface of the aluminum doors and windows. When the surface temperature of a solid (such as glass, window sashes, or window frames) is lower than the dew point of the surrounding moist air, water vapor in the air turns into liquid water and condenses on the cold solid surface, resulting in condensation. When condensation is severe or cannot evaporate quickly, water droplets will flow down along the edges of the glass. Condensation is less likely to occur on the sunny side of aluminum doors and windows, but it is more common on the shady side, especially in kitchens and bathrooms.

Most people think this is a problem with insulating glass? Actually, that's not entirely true. First, let's talk about the following points:

1. Insulated Glass and Vacuum Glass

Often, people mistake "insulated glass" for "vacuum glass", or simply think that "insulated glass" is the same as "vacuum glass", which is incorrect. The insulated glass used in our home's aluminum alloy windows usually consists of two layers of glass. These are joined together by an aluminum spacer, desiccant, and sealant, creating a natural air layer in between. There is air between the two layers of glass, forming a dry and relatively isobaric space, not a "vacuum".

Vacuum glass, on the other hand, belongs to the category of special glass. The layer between the two panes of vacuum glass is indeed in a vacuum state. This type of glass is more expensive to produce and is only used in places with special requirements. Due to its high cost, it is not commonly used in ordinary households. It is more frequently seen in aircraft, high-speed trains, military facilities, special laboratories, and training rooms. This is because vacuum glass is highly energy-efficient and insulating, has excellent soundproofing and noise reduction capabilities, and can prevent condensation.

2. Why do sealed double-glazed aluminum windows with thermal breaks get condensation while slightly drafty plastic steel ones don't?

Perhaps you are puzzled. You thought that the double-glazed aluminum windows with thermal breaks had good insulation and sealing properties, so you replaced the old windows with them. However, you found that condensation appeared on the glass and water dripped onto the windowsill. This situation never occurred with the slightly drafty PVC windows before. Could it be that the quality of the double-glazed aluminum windows or the sunroom installed is substandard? Thinking of this, would you immediately call the window manufacturer to question the quality of the double-glazed aluminum windows or sunroom they installed?

Does the condensation and air infiltration occur inside the glass cavity or outside the glass (indoor side)?

If condensation, air or fog appears inside the hollow glass cavity, or cracks or obvious spots appear, which cannot be wiped off no matter how hard you try, then this is indeed a quality problem. It may be that the glass is not sealed well or the desiccant is not up to standard. In this case, you can ask the aluminum windows and doors manufacturer to replace it free of charge.

If condensation appears on the inner surface of the double-glazed aluminum window and drips onto the windowsill, this is actually a normal natural phenomenon, especially when there is a large temperature difference between indoors and outdoors. This situation is more obvious. Car owners should be more familiar with this condensation phenomenon on the glass. When the car is not ventilated, the car windows will also be covered with a layer of fog.

When the indoor environment has a certain temperature and humidity, the air temperature is higher than the surface temperature of the condensing object, and the surface temperature of the object is lower than the dew point, condensation will occur. There is an intersection between the three. That is to say, under the same indoor temperature and humidity conditions, if the temperature of the indoor side of the aluminum door and window and the indoor side of the glass is relatively low, condensation is more likely to occur.

Under sealed conditions, the better the thermal insulation performance of the room, the more obvious the water vapor adhesion on the glass.

When the room is sealed and the window is not opened for ventilation, the indoor heating temperature is high and the outdoor temperature is below zero, the moisture in the indoor air will condense into water droplets when it encounters the window glass. When the water droplets accumulate to a certain extent and exceed the adhesion, they will drip down. The greater the temperature difference between indoor and outdoor, the higher the indoor humidity, the more condensed water, just like netizens said, dripping like light rain.

Someone may say: "My home has floor heating, the air is dry, where does the moisture come from?" But in our normal living environment, the air itself contains humidity, the gas we exhale, and the various gases generated by indoor activities, such as the breath exhaled in winter, all contain moisture, which is normal humidity. However, the humidity in the kitchen, bathroom, and shower room is the highest.

Under the same conditions, PVC windows with poor sealing tend to have less condensation. This is because the slightly ventilated PVC windows allow outdoor air to penetrate, thereby adjusting the temperature of the inner glass surface, reducing the temperature difference, and naturally drying the condensation, making it less obvious. However, this will cause the indoor temperature to drop significantly and is not energy-saving.

This just verifies the principle that vacuum glass does not condense: "Vacuum glass has extremely strong thermal insulation performance. In the cold winter, even if the outdoor temperature drops to -30℃, the temperature of the indoor glass surface is still close to room temperature, which is much higher than the condensation temperature." This sentence means that the greater the temperature difference between the indoor glass surface temperature and the room temperature, the easier it is to condense; the smaller the temperature difference, the less likely it is to condense.

What should we do if condensation and frost appear on the glass and glass top of the sun room in winter?

The following methods can alleviate the condensation of glass without additional cost:

1. Ventilation

Opening windows for ventilation every day can reduce air humidity and take away moisture generated in daily activities. Dew on the glass can also be dried naturally.

2. Use exhaust fans

In spaces equipped with exhaust fans, it is recommended to use exhaust fans appropriately to reduce or eliminate condensation problems.

3. Wipe the glass

If you feel cold when opening the window for ventilation, you should frequently wipe the dew on the glass with a cloth to prevent excessive condensation from forming water streams and damaging the interior decoration on the windowsill or floor.

4. Apply anti-fog film

Applying anti-fog film on the glass can solve this problem. I tried applying anti-fog film on the bathroom mirror and found that it rarely fogged. Although this will increase some costs, it is worth a try.

5. Other methods

More effective solutions may require higher costs, such as installing a dehumidifier, ventilation system, or installing special performance glass in the home, such as self-heating anti-fog glass or vacuum glass.

Even passive windows with the slightest possibility of condensation have a condensation resistance rate that depends on the indoor relative humidity. If the relative humidity exceeds 40%, in outdoor temperatures of -20°C or colder, even better high-performance glass will condense.

For aluminum doors and windows, the main cause of condensation is excessive indoor humidity. Research shows that each square meter of a house requires 40 kilograms of water during construction. The evaporation of such a large amount of water takes a long time. If the house is not fully dried before occupancy, activities such as bathing, cooking, and growing a large number of plants after moving in will further increase the indoor humidity. When the indoor humidity exceeds the saturated moisture content in the air at a certain temperature, the moisture in the air will condense and precipitate on objects with lower temperatures, resulting in condensation. Therefore, even if the doors and windows are well insulated, condensation will still occur if the indoor humidity is too high.