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Condensation Frustration: What to Do When Your Windows Fog Up

By Angell Aire /

Come winter, and your windows can turn into a veritable waterfall. They can just show up beads of condensation, or turn into wall-to-wall frost that needs scraping off each morning. If you have double- or triple-glazed windows, you may find that there’s no condensation on the insides; you still could have plenty on the surface. If you’re sick of seeing condensation forming on your windows, trickling down the sills and running down the walls, it’s time to do something.


Understand why window condensation happens

There are three different variables that go into determining your windows’ ability to fog up: the temperature outside, the temperature inside, and the humidity level that you maintain indoors.

Whatever humidity your indoor air may contain, it will reach its dew point when it comes into contact with the cold glass of your windows, condense into liquid water, and eventually freeze into frost crystals.

If you don’t want condensation, you will need to make sure that you remove at least one of the contributing factors to this situation. Since you can’t do anything about the weather outside, it will have to come down to either the humidity in the air indoors or the temperature of the glass.


Heat to beat the fog

When the temperature outside drops, turning up the thermostat indoors can help keep condensation from appearing. When there is enough warmth, it can gently heat up the glass on your windows to a level above the dew point. All things remaining constant, a warmer house can translate to less condensation on your windows. Of course, this can make your home too warm for comfort, kill your plants, disturb your pets and send your energy bills soaring.

This is why home-improvement stores sell baseboard heaters. If your home doesn’t have heating installed under each window, you should invest in such units. While your home in general can be whatever temperature you set your thermostat for, the windows themselves will be warm.

An even more energy-efficient solution exists — you can put the same kind of glass heating element on your windows that you see on the rear windscreen of your car. Defogger brands such as T-Stripe are popular. The energy draw tends to be minimal, and the warmth will keep your windows dry.


Lower your home’s humidity levels

The colder it gets outside, the more careful you have to be about the humidity levels indoors. The higher the humidity level, the greater the amount of moisture that will deposit your windows. If your furnace has a humidifier attachment, it would be an idea to shut it off.

There are other ways to help keep humidity levels under control. Stop keeping firewood indoors (it’s a termite risk, anyway). You should put your potted plants away in a separate room, too. Both items release moisture to the air. You should also look at the basement. If it’s damp, it will release moisture into your home.

Ventilation fans in the bathrooms can take out the prodigious quantities of steam released over the course of the average shower, and a powerful kitchen hood can take out cooking vapors. The rooms that contain your washing machine and vent-less clothes dryer should have ventilation fans, as well.

It’s important to design good air flow around these ventilation installations, though. Each room with a ventilation fan should also have an air inlet. When you have a ventilation fan working, but no air inlet, the force generated by the fan will create negative pressure in your home. This will attempt to pull air in from any source possible — usually, the clothes dryer and furnace. Air coming in from the furnace, especially, can be tinged with carbon monoxide.

If none of these solutions seems right to you, you can always buy a dehumidifier. Certainly, drier indoor air will cause discomfort and dry skin; to the extent that it doesn’t, though, running it can help.


Do you have new windows?

If your condensation problem seems to have started only after you had new energy-efficient windows installed, it only means that the windows are airtight, and able to cut off moisture leakage that the old windows allowed. You need to double down on improving your heating and lowering humidity.


If all else fails, call in a condensation investigation expert

Expert window installation companies are able to investigate condensation situations, and perform high-tech tests to offer remedies. They can use endoscopes to look into your walls for insulation failures, for example, or find sources of humidity that you may have overlooked.


Putting an end to condensation is more than just a cosmetic issue. Not only can dripping rivulets of water ruin your walls, they can promote the growth of harmful rot and mold. It’s important to understand that condensation, in most cases, has nothing to do with the windows themselves. Rather, it has everything to do with the house and your lifestyle choices. It can take an expert to look into the causes and work out a solution.



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