Window Condensation


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Window Condensation

Many homeowners have concerns when they find condensation built up on the inside of their windows. The natural reaction is to assume that the window is somehow allowing the moisture or wetness to leak from the outside to the inside of the home. Typically, this is not the cause of the built up condensation.

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Window Condensation Explained

Condensation is essentially moisture found in the air. It occurs when warmer moist air meets a cooler dry air. It's the same basic principal as taking a shower and having your mirror fog up. This is the same idea with your home windows, when warmer air meets the cool surface of the windows glass, it causes condensation to form. The condensation forms on your windows because the surface of window glass has the lowest temperature of anything found on your walls.

During the hot summer months, condensation can be found on the outside of the windows, while in the cold winter months, condensation will occur on the inside of the window glass. In general, these incidences of condensation are harmless (but often annoying). However, condensation found between the panes of glass (assuming a dual pane window) is a legitimate cause of concern.

Condensation And Energy Efficient Home

The issue of condensation has become more prevalent with the advent of more energy-efficient homes and products. Today's homes are much more energy efficient and thus better at trapping the warmer heat inside the home. The result is a greater incidence of interior condensation on the window surface. Older and less energy-efficient windows let more heat escape from the house and therefore there was less moisture inside and less condensation.

Reducing Condensation In Your Home

So how do you reduce the amount of condensation in your home? The easy answer is to control the amount of humidity that exist within the home. If you notice condensation forming on the inside of your windows during the cold winter months, you can crack the window for several minutes and release some of the built-up moisture from inside the home.

Other solutions include running your exhaust fans a bit longer in the kitchen, laundry room, bathrooms, etc. Homeowners can also use a dehumidifier to reduce the moisture in the home and they may also consider opening their blinds or drapes, which will allow the air to better circulate against your windows.

When To Be Concerned

Condensation should only form on the inside of the inner pane or on the outside of the outer window pane. It should never be found between the two panes of glass. If you do find condensation between the glass panes, it is an indication that the airtight seal is broken and you will most likely need to replace one or both of the glass panes.

A cost savings approach is to call a local window glass repair company and get a price quote to replace the glass - tell them the type of window, the brand of window, and the size of the opening and most companies should be able to give you a price quote right over the phone. This will be a great starting point to deciding whether you need to replace the entire window unit or whether it is best to simply replace the glass pane.

Window Condensation

Dane, I recently had some series 80 windows installed at my stepmothers house. We have a 3-4” strip of condensation periodically showing up on the lower Exterior of one window.This is on a 8-0 3-0 window. The strange thing is there is a 7-0 3-0 just 10 ft. away in the same line and the same roof overhang facing the same direction.

Any ideas?🤔 I can gather pictures if you need. 7 other windows installed and they don’t do this.


Ken - Homeowner - from 2020

[Site Editor's Answer]

Ken, I'd call up a local window company and ask for a bid for replacement windows. Then when he comes out, ask him to take a look. It doesn't cost you anything and while you're kind of duping the rep, who knows, you may have to get some windows down the line. He can probably tell you what the likely cause is.

Condensation on the outside of windows typically happens in the spring or fall when warm days turn to cool nights. Why it's occurring on one window and not the others...I can't say.

Dane - Site Editor - from 2020

Window Condensation Help

It is only October and I have moisture on the windows about an inch higb. Temp outside 55 temp inside 68! I have never heard of it happening like this unless the humidity is real high outside and the temp inside is real cold from running air! Also there are round knobs at each end of the window frame, not sure what they are for! My parents have regular Anderson windows that have a one piece flat sash that u can clean. These are two plastic pieces with drain holes that plug up and it takes forever to get dirt out of the split between the two groves ! Never saw a sash like this. Please help , just purchased house and can not afford to replace the new windows! I am wondering if they are installed correctly? Installer said moisture is normal!

Thank you much,

Lorelei - Homeowner - from 2015

[Site Editor's Response]

Lorelei My advise would be to hire someone local to come out and take a look at the locking mechanism and the windows in general, especially given the time of year and the weather changes that will happen over the next month. I did a quick search for Jax Bldg Supply and a store in Michigan comes up. Is this where you are located? If so, call them and see if they know which window you purchased and whether they can help with your issue(s). They may work with installers who you might want to pay for an initial hour to come take a look and see if there is a low cost solution to your condensation problems.

Dane - Site Editor - from 2015

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