My grandmother has had this house for 50 years and never had this problem... she just had her main level bathroom remodeled so she can take showers without going down stairs... there was an exhaust fan installed in the bathroom and I'm wondering if that has anything to do with it... she had the problems since the remodeling when she is using or not using the shower... she has been visiting with family for the past week and nobody has been at the house and her son went to check on the house and notice the condensation on all the walls... do you thinks it's the exhaust?

Condensation means you hit the dew point which rarely happens indoors unless humidity is very high or you have a very cold spot reaching the back side of an outside wall. Was the condensation on an outside wall?

Yes the walls that have condesation are outside walls and a little on the ceiling close to the outside walls... ask all the questions you need brother

I am thinking that whoever did the remodel did not insulate the exterior wall properly. Cold air is getting inside the wall and touching the back side of the interior wall.

But the moisture is on the walls in the livingroom and bedrooms on the same level as the newly remodeled bathroom... there was nothing done to the walls with the condinsation on them... sorry if I didn't make that clear in past post... she actually just told me that there is no condensation on the bathroom walls but on all the outside walls

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there was an exhaust fan installed in the bathroom and I'm wondering if that has anything to do with it

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You have told us about the exhaust fan being installed but not where it was terminated.
Did it terminat in the attic or was it run out the roof? Let me know, Tom

Yes the exhaust goes outside through the roof straight up with a cap... not sure if it has a check valve or not, don't know if that would have anything to do with it or not

I did not realized you meant all of the walls, thought we were just in the bath. OK nobody there for a week so where does the condensation get its moisture? Is there a humidifier on the furnace, what temps are you seeing outside at night?

Is the exhaust for the fan even hooked up? May not be and pumping humid air in the ceiling and letting cold air in through the vent stack

The exhaust fan is hooked up to the outside going straight up through the roof and she does have an humidifier on the furnace and have currently shut it off to see if that is the problem... outside temp was roughly 30 to 35ºf