Where the drapes closed overnight? Good air circulation at the doors/windows?

The edge of the window is where it is more thermally bridged. If it's -10 outside, you are going to need to get the RH lower. That is just too high for those temps.

https://pacificheatingcooling.com/2018/12/27/the-proper-humidty-level-in-the-home-and-how-to-control-it/

Figure out what the actual RH (probably in between the two to hazard a guess) and adjust accordingly. At -10 degrees exterior temp, you need to be 20% or less. It's its 34% (halfway point), there is no way that window isn't forming ice.

And why builders in Chicago are using double pane glass is beyond me. Honestly.

There you have it. Absolutely nothing I could add to the above two responses.

Any thoughts on long term impact? hardwood rotting? mold? or just keep drying and nothing to worry about?

can i caulk outside or any other preventive measures to take?

thank you so much!!

next time will go triple pane - but almost ever builder uses double pane and most dont have these issues so im not sure why i am having them

The thermal bridging of the sash isn't something that will be impacted by exterior caulking. Open the blinds and stir the air.

Not sure I agree about the double-pane vs triple-pane. I think it's more about the quality of the windows as well as a good installation (we don't know about the OP's new-construction home windows installation quality). I am in a Chicago suburb about 40 miles north of the city, not too far from the Wisconsin border. We have double-paned Marvin windows, but they are Marvin Ultimates.

So our temps have been in the negative-teens at night the last 3 nights (wind chills of -20 to -33). We do have a whole-house humidifier which I turned down when the cold got so bad. Hygrometer says it's about 23%. We also have kept the drapes and blinds open a few inches throughout the house. No condensation on any of the windows except in my daughter's room because she hates the sunlight coming in in the morning so kept her cellular blind entirely closed. That window had some ice forming on the outside of the window, but is dry on the inside. I realize this is not helping the OP, but I just wanted to mention the part about double-panes being sufficient - depending on the window and the installation.

Well...windows appear, from the few photos, to be condensing on the spacer bar areas of the sash. That is the weakest point in the window from a thermal standpoint and would most directly be improved by glazing selections (i.e. triple vs. double for higher CR numbers).

Gotta agree with WOW. The double vs triple pane is pure science and is evident in the raw data. The spacers are obviously important as well. The Types of Low-E coatings used and where applied make a difference as well. If they used the Low ERS glass package this could be part of the problem.

We have large Marvin Essentials low-E on our house that was finished June 2023. Last week we had five days of single digit outside temps. Inside temp is around 68-70 and RH in upper teens to low 20’s. We had a little bit of ice forming on the bottom of windows but only on the windows that have shades which are down much of the time. This was for both fixed and casements. All of our shades are top down/bottom up so we just kept both top and bottom of the shade open about 4” to air wash the windows and that solved the problem for us. I’m just a homeowner but I don’t think this was a problem with the window.

Agreed. Wasn't a window issue. Bit too much RH in the home and a bit too little air circulation is all.

And...anyone in Chicago should have triple pane if you ask me.

Great advice from the pros above.

- RH is too high for the exterior temp. Get that down or take measures to warm up the glass.

- Yes triple pane would be measureably better. Windows are rated for Condensation Resistance as Oberon alluded to, and there is a tremendous difference from double pane with surface 4 low-e (worst) to triple pane (best).

- The Marvin Elevate double hung is far from the most airtight window available, but pictures don't show anything above and beyond what would be expected in those conditions.

“Our humidity is 30% according to a manual hygrometer (38% according to NEST).”

”My humidifiers are off (I have 2 furnaces in the home).”

As I said in my earlier comment, I live fairly close to the OP, and last week experienced the same daily sub-zero temps. Our humidifier was on, but turned down so that we were at low-20s humidity. At such cold outside temperatures, the air was very dry. Perhaps the real problem is that when outdoor temps were -5 to -15°, the OP has indoor humidity levels of 30-38% with the humidifiers OFF. Why and how is that happening?