Home>Discussions>DOORS & WINDOWS>Window Condensation, A/C & Mold??
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Re: Window Condensation, A/C & Mold??

I just happened to instal some counter tops in a house a couple of weeks back in a house that was having this problem. and since you say it dates back to the time that the house was built I would assume that the cause could be the same.

the manufacturer of the windows sent a rep from alabama and was there while I was finishing up and so I heard the conversation between him and the home owner. the cause ended up being improper instalation. the outside of the window was never properlly sealed the rep said that as the window is put in it should be set in caulk and then the edge of the window framing should taped to seal it off to the house wrap.(tyvek) He explained that with out that process cold outside air was able to enter the window framing and this was the cause of the condensation, but if it was sealed off then it became an insulation barrier.

Re: Window Condensation, A/C & Mold??

Surface temperature also plays a huge part in this.
Windows surfaces are one of the coldest areas of the outside walls.

For example ...... today the outside temperature is at 10 degrees F and using a digital infrared thermometer I took temperature readings of the glass surface of a window and also the surface temperature of the adjacent wall.

The wall gave a surface temperature of 60.7 degrees and the window surface was 50.9 degrees.

Since the window's surface is a full 10 degrees colder than the wall surface the humid air in the room will contact the window surface and will condense.

The higher relative humidity inside the home the increased moisture will form on the window's surface.

Re: Window Condensation, A/C & Mold??

I'm going to say dehumidify the house first. Start with a decent vent hood for the kitchen and good fan in the bathroom(s) vented to the outside. Then put a dehumidifier in the house. Humidity indoors should never be near 50%. I have a friend with compromised breathing issues and her doctor says humidity indoors should only be 20-25% at the most.

Remediation is a good idea since there's damage to the wood surrounding the windows. Check out the resources from the current project house to learn how.

Re: Window Condensation, A/C & Mold??

Dehumidifing will help but you need to find the source.
Here is an infrared picture of a poor window installation (new house).
The blue is cold air getting in.Using vent fans and the like may be worse if there is a hi infiltration area. Notice the outlet below the window-a simple gasket or yellow foam will fix it.Cold air could be coming in from many places.
A Picture says 1000 words.

Re: Window Condensation, A/C & Mold??

Here are some recommended humidity levels to allow safe levels with comfort.

Outside Air Temperature (ºC) .......... Maximum Inside Humidity (68 F)

–30º or below ............ ............................... 15 percent
–30º to –24º ............................................. 20 percent
–24º to –18º .............................................. 25 percent
–18º to –12º ............................................... 35 percent
–12º to 0º (32 F)..........................................40 percent

Re: Window Condensation, A/C & Mold??
debbysewn wrote:

I have a friend with compromised breathing issues and her doctor says humidity indoors should only be 20-25% at the most.

I guess it is a matter of personal preference. When our humidity gets below 40% my nose and throat really dry out. We keep a pot on the stove all the time boiling off about 4 gallons of water per day.

Re: Window Condensation, A/C & Mold??

You need to keep your humidity down around 35 to 40%. You also have windows that are 20 yrs old and don't have the insulation value of modern windows. Condensation is a matter of dew point. You need two things, high humidity and low glass temperature. Sounds to me that you need to correct both problems.

Best of luck,

Re: Window Condensation, A/C & Mold??

Thanks to everyone for the suggestions. We've taken steps to ensure our vent hood fan in the kitchen is always running while cooking dinner and the casement window slightly cracked. We've also kept the bathroom doors closed and the bathroom windows open as well after showers/baths until we can install some exhaust fans.

It seems it's just something I'll try and manage and see where it goes from here. Worst case, I'll look into a dehumidifier - can someone recommend a well functioning quiet one? - to reduce the humidity. It's only been a short time, but seems to be okay so far.

One thing I failed to mention. I did purchase two new Andersen windows for the two bedrooms that face West. They came in too late to install last year so they'll be done in the Spring. In the event one is truely leaky (I'm suspicious of one), I'll know for sure. Besides the wood staining from the condensation and the possible lack of insulative properties after 20 years, we were interested in the UV sun protection the new windows will provide for the rooms facing West during the summer months. I'll be able to check the insulation/area around the window and ensure the new ones are properly installed and sealed. We'll likely move our way around the house and replace all the windows over time too.

Also, we don't have mold anywhere in the house other than, on a rare occasion, along the bottom of the top and bottom panes of the windows. The mold only develops if the moisture is left unattended and doesn't dry for a period of time. The damage is mostly darkening of the wood from repeated moisture. I don't believe I have a need for mold remidiation.

Again, thanks to everyone for the homeowner education. I appreciate each and every response. I've seen other forums where questions go unanswered but I'm glad that's not the case here. I hope to be able to return the favor.



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