Condensation on windows only w/ temps 20F or lower
I'm getting condensation on all my dual pane wood casements when the outside temp. is 20F degrees or lower. Otherwise the windows stay dry. The humidity in the house is 35% to 38%. This two story house was built in 2000 and I recently insulated the attic with closed cell foam and cellulose, but I've had this problem since I moved in this house 6 years ago.
Is this a sign of too much humidity or just poor performing windows? I don't think that my humidity level was too high or is it ?
This house is equipped with a high efficiency gas furnace that does not draw fresh air from the outside. Gas stove and electric dryer. All bathrooms have functioning exhaust fans that are used after showers.