In a cold-climate home, the combination that actually stopped interior window condensation and overnight icing for me was keeping indoor humidity in the 30-35% range during the coldest months and adding interior storm panels to the most problematic windows. I learned this after helping a homeowner who kept wiping ice off their bedroom windows every morning, even though they had a newer furnace. Once we lowered humidity slightly and sealed interior storm inserts tightly, the condensation disappeared almost immediately. From my experience, the single biggest difference wasn't aggressive ventilation or over-drying the house—it was improving the interior air seal at the window. Interior storm panels created a warmer inner surface and blocked warm, moist air from reaching the cold glass, which stopped icing without making the living space uncomfortable. In one case, a customer tried running bathroom fans constantly and ended up with dry air and static shocks, but still had window frost. After installing interior storm panels and setting the humidifier to a steady 32%, the problem was solved within days. The practical takeaway is that condensation is often more about temperature and air leakage than humidity alone. A moderate humidity target paired with a tight interior seal works better than chasing lower numbers. If you're still seeing ice, check for small gaps around window frames and make sure the interior panel is fully sealed—those tiny leaks are often the hidden culprit.
The main thing that's helped in my home with preventing window condensation has been my windows. I had them all replaced a few years ago, and I chose to go with triple-pane windows. Previously, I had double-pane windows and they did a decent job, but I had noticed that in their last few years, there was a good amount of condensation that would form. So, I decided to invest in an upgrade and go with triple-pane windows, and they've been fantastic. I never deal with condensation problems, and my house has significantly better insulation.