"c_shah" wrote in message
oups.com...
I live in a suburb of Chicago, It is around -3 degree Fahrenheit, I
wake up this morning and found ice on all of my bedroom and kitchen
windows. What does this indicate? Do I have leaky windows? I kept
humidifier (aprilaire - attached with my furnace) to 35%.

Sounds about normal for that combination of outdoor temperature and high
humidity. Try setting it a bit lower if it is a problem.