Preventing Condensation on Windows
I recently replaced the windows in my house with double paned low e glass because previously the fire rated glass had a defect with the gel inside of it. These windows are on the third story and look downhill and have a view of the water.
After replacing the windows, I noticed in the winter months, in the morning there was exterior condensation on the windows, which I realize now was a risk with the positioning of the window to the open sky and looking downhill. This is a bit of a nuisance since I enjoy looking out at the views in the morning. The condensation does eventually go away though. This previously did not happen with the old windows. I have the opportunity to replace these windows with something else that doesn’t create this issue.
Does anyone know why fire rated windows wouldn’t have this problem? I’m just curious so I can specify the right product. Are there anti condensation windows? A quick google search shows there’s some product out of the UK but is that not common in the US.
Is there another product I could put on the existing windows that would prevent the exterior condensation if I don’t want to replace it? These are 30 ft high and aren’t operable windows, so a permanent film or coating would work best rather than a spray that would have to be reapplied.
Any insight or help would be much appreciated as I don’t know much about this. Thank you!
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Replies
Hi Yolanda,
If you end up going the route of replacing them, this is a helpful guide that includes a section on condensation resistance ratings: Buying Windows. “The range is 1 to 100; the higher the number, the less likely a window is to gather condensation on the glazing.” Note that this is a voluntary rating that won’t be listed on all products but it’s something to be aware of and to look for.
Thanks Kiley. I believe that rating only applies to interior condensation and not exterior, but appreciate the link
You say there is exterior condensation on the windows how sure are you that it is on the exterior and not in between the two layers of glass?
Is the glass vertical or is it sloped somehow?
Walta
Hi Walter - I am sure its on the exterior of the glass. And have read of others having this issue with efficient windows with similar positioning to mine (open sky, facing downhill). The glass is vertical and not sloped.
I'm curious why I didn't have an issue with the old fire rated windows. Are there properties of those kinds of windows that could make them be more anti-condensation?
Exterior window condensation is basically dew. You are seeing it now when you didn't before because you have more efficient windows that are not letting the exterior glass get as warm as it did with your older less efficient windows.
The glass radiates heat to the open sky at night lowering the glass temp below the dew point and there isn't enough heat escaping through the more efficient windows to warm the glass enough to prevent condensation.
Thanks Greg. I appreciate the explanation and lines up with other research I’ve read. The views are important to me so I’d like to replace the windows with ones that won’t have this issue. The prior windows were fire rated. Do you have any idea what properties those windows would have that would make less exterior condensation to occur on the exterior? Is it just that they were less efficient?
Do you know of any anti-condensation windows?
Without knowing what you had in the previous windows there really isn't any way to compare directly, but probably they were simply less efficient.
Cardinal has a coating specifically designed for exterior condensation called X89. This is not something that can be applied to existing windows, it's applied to the glass during manufacture and it is permanent.
Look at page 23 of the link
https://www.cardinalcorp.com/source/pdf/TGG_V3.0_Final_11-5-2020.pdf
Maybe a coating from the greenhouse world: https://www.plantproducts.com/us/images/PRINT_-_AntiCondens_Sheet__EN_2020.pdf Looks like it is to be applied annually.
Thank you both for the helpful suggestions!