have been noticing condensation on my window glass each morning, but when I open my heavy curtains, the condensation will disappear. Never had this problem with my old windows. Thank you.

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    Were the previous windows double-paned glass? Are the new units as well? Is the gap between the two panes of glass the same on the old and new ones? Any other differences between the two windows? – OrganicLawnDIY Mar 13 '17 at 17:49

This is normal. Your indoor air is humid, so when it reaches a cold surface (your window glass) condensation appears. The heavy curtain facilitates this by reducing air circulation across your window, which blocks heat and air flow around the window, but does not seal out humidity. The window gets cooler, and water condenses on it.

When you open your curtain, the window gets warmed up from your room air so some of the condensation evaporates. This probably happens when you wake up, so you're also opening up other doors and windows, moving air around the house, and helping the humidity levels even out.

As long as you're regularly relieving the humidity build up and it isn't dripping (which can cause rot, e.g. on a wooden window frame) this shouldn't be a problem.

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  • One more thing - even with good double-pane windows, a storm window outside can be helpful with reducing condensation. If you have one, make sure it's closed as firmly as possible. – Shimon Rura Mar 15 '17 at 14:49

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