window condensation

Specific Inspection Topics Interior Inspections
1

Anderson Thermal insulated windows (2 panes of glass), no fogging, a breeze could be felt between the upper and lower windows. Moisture check on wall around the entire window was negative. Windows appeared to be properly flashed and J channel was installed(vinyl siding)

I wrote it up as condensation observed on window and window trim. Weather stripping appear to be worn. Recommend replacing weather stripping.

What would you say?

2

i see this a lot… often on windows with heavy curtains or shade where not inside air gets to the windows… combination of humidity in the home and poor weatherstripping… in our own house we get this too…

we had to seal some of the areas around the window with a temporary caulk until we can replace weatherstrip. we actually had icing. no much problem now… we make note to open the heavier curtains during the day to dry and moisture that may start… we have HWBB heat vs. FHA too which may make a difference.

3

You explained it well .
I would also hazard a guess that this Home could have a higher then normal humidity level.
We also recommend all curtains do not go to the floor and should be 4 inches of the wall to the top to give better air circulation.
…Cookie

4

I’ve seen it most in bathroom windows. Just curious, where was this one.

5

Good practice. But when going to bed, open the curtains then (if privacy is not an issue) as the glass will get its coldest at night. Let the heat and convecting air get to the glass to keep it warm. Even with normal winter interior rh’s, condensation will occur on regular sealed pane glass in the coldest nights.

In 1989 (lived in another province then), I was hired by a consulting firm to work in Halifax (I live near this city now) to work in a cross-country IAQ study (condensation, mould, combustion gas spillage/backdrafting, etc) funded by gov’t. One of my functions was to go to selected homes early in the morning and view window condensation; measure window glass temps, interior rh, air temps; leave air sampling tubes, etc.

My own observations of casement, single/double hung vertical sliders was that there 2 design problems with window sashes with sealed panes of glass. One was window geometry: there are triangular “dead air” pockets at the meeting rails of the vertical sliders and the glass/sash joints of all sashes. During the night, as it gets colder, a gentle convective drop of air from the top of the window to the floor develops with the air being coolest at the bottom of the windows (it has slowly cooled as it falls down the glass surface).* The air in the pockets is dead and not bringing heat to the glass here. The glass cools below the dewpoint of the air in the pocket, hence condensation/ice forms.
*That’s why the condensation is the bottom and maybe a bit up the sides of the sashes although the sashes are built the same on all sides.

The coldest part of the window is the lower glass at the square tubular metal spacer- this glass/metal/glass sandwich conducts heat outward so fast it that never gets replenished quickly causing this inner glass to get below freezing, at times even in LOW “E”/ARGON sealed panes!! The LOW “E”/ARGON features can’t work in the sandwich area. For about 20 years, there have been some type of “warm edge” or insulated spacers available that try to help this area stay warmer, preventing condensation. The Tremco “Swiggle Strip” was one of the earlier ones but like many new inventions had some longer term problems.

6

3 of the 4 second floor bed rooms.

7

That makes too much sense, all the condensation was in the bottom corners of each of the affected windows. Thanks for the in depth explanation.