Windows may serve as visible areas for moisture to condense, warning you that there is too much moisture inside your home.

Windows do not cause condensation.


Water and/or frost on your windows is called condensation. Condensation happens when warm moist air comes in contact with cooler dry air. Just the way a cold can of soda will turn wet, or your mirror will steam up after a nice hot shower. Your windows can sweat the same way when there are temperature changes around them. In winter, when your high-quality vinyl windows are efficiently keeping cold air out and warm moist air in, condensation may appear as fog or moisture on the glass. Condensation does not indicate a problem with your windows; quite the contrary. It means you’re holding in warm air like never before. But you’re holding in humidity, too. That’s the problem.

Do windows cause condensation?

No. Windows do not cause condensation; they simply are doing what they are designed to do. By keeping the warm air in your home the windows also stop the humidity from escaping and that humidity becomes visible on the glass. Windows themselves do not cause condensation, but they are an indicator that humidity levels are too high.

My old windows didn’t have condensation, but my new windows do. Why? Are my windows defective?

One of the reasons you had new windows installed was because you wanted windows that were more efficient than your old windows. Chances are that your older windows were drafty and leaking air. So the reason your old windows did not accumulate moisture is because they were doing very little to keep the heat (moist air) inside of your home. The condensation on your windows is an indicator that your new, energy efficient window is working by locking in the warmer, moister air inside your home, not allowing it to leak out like it did with your old windows. No, condensation on windows is not the fault of the window.

Why windows are normally the first place condensation is noticed in a home?

Windows typically are the coldest objects in the house in wintertime. Windows do not cause condensation, but because glass will generally have the lowest temperature in your home, it is the place that you will almost always notice condensation first. Just like the mirror or pop can, neither of which is defective or leaking, they are just a cool surface on which the moisture in the air will condensate on.

Why does the condensation collect on my windows and not on my walls?

The fast answer is because humidity cannot pass through the material glass while it does pass through sheetrock, wood, siding and even sheet plastic. Also your walls are constructed in our area to be 4 or 8 inches thick while the insulating space in your glass is only 5/8 inches thick making glass a very inefficient insulator.

What is raising the humidity level in my home?

There are many activities happening inside your home that raise the level of humidity. They include but are not limited to: showers, dishwashers, clothes washers & dryers, dripping faucets, open fish tanks, cooking with gas, overuse of humidifiers, excessive plant containers that require watering, damp basement/crawlspace, simple breathing – a family of four generates 6 litres of water vapor a day.

Can I reduce the condensation on my windows?

Yes. In order to reduce condensation, humidity must be controlled and air movement must be generated. As the exterior temperature drops, the humidity level needs to decrease if condensation is to be controlled.



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