Houses built today are much better insulated and more draft free than thoses built in prior days. This is a good thing; but it can cause some minor problems to the homeowner.

There is more moisture in these better sealed homes which will accumulated on the interion of window panes. This moisture can be traped between the glass and curtins/drapes/binds/shades. When this happens mold/mildew will sometimes form on the window sash/frame. This is especially noticed on the north side of the house.

This can easily be advoided by creating air circulation between the glass and the window treatment - don't close the drapes all the way and leave a small gap between the shades and the sills.