Humidity Level? At what % should the humidity be in a home?

At what % should the humidity be in a home?
Answers:    For winter, 50% - 55%. For summer, 45% - 50%.

If you procure much above 55% you run the risk of mold, which can cause respiratory problems. If you seize much below 45%, you run the risk of sinus problems and other respiratory problems.

The higher the humidity, the furnace you feel and visa versa. I similar to 55% while heat's on, 45% while AC is on. If neither are on, I usually don't monitor the humidity much. (In winter, 55% humidity at 70degrees F feels in the order of the same as 74degrees F at 50% humidity. Keeping the humidity where on earth I want it saves me money on heat and cooling.)
I would say 40-50% is the minimum. If you bring too high, the house will smell of mildew.