All my windows now leak air have severe condensation.
All my windows, 17 in total, installed by 24 Hour Thermal Glass Insulation started to develop severe condensation and air leak problems 5 to 10 years after installation, as all the inner seals have broken down. The large picture window attached here I can barely see out of, my bedroom window is even worse. Even in the summer the condensation remains in the windows.
Air leakage (despite re-caulking it multiple times) at the bottom of this window is so bad that solid ice forms on the inside if the temperature drops below -10C and I get a pool of water that collects on the floor each day. And yes, we keep the humidity in the house strictly controlled to be between 35 to 40%. A sliding door we had installed 5 years ago on the same floor by another company has no air leaks and no condensation. It's too bad this site does not allow you to post images. Check out theire Google reviews.