I am in the process of pinning down why my main living floor is about 10% to 15% more humid than most parts of my home. I'm wondering if anyone may have a similar experience, ideas for what to investigate.

This is a high ranch built on a slope in Dutchess County New York, surrounded by trees, loamy soil. Siding is vinyl with vapor barrier underneath, architectural shingles, block foundation, built in 1984. I moved in last February so this is my first fall here.

The basement and garage under the home, are coming in at approximately 50% humidity — on today, a 90% humidity, 50 degree fall day. There is some efflorescence around basement and garage windows, minor signs of water intrusion around garage walls where the ground slopes down toward driveway. No flooding has occurred in either area, no sump pump here. Basement is paneled and carpeted and has no especially strong musty odors.

Main floor windows regularly have condensation most mornings since temperatures have dropped. They are single pane wood Marvins with storm windows, original to the house. Window salesperson came and said they are in really good shape.

Today, first floor is showing 60% to 65% humidity. The two bedrooms directly above garage average 3% to 5% more humid than the rooms above the basement area. Attic humidity is 77% right now.

We have water baseboard heat. Dryer and bathroom vents appear to be properly routed to outside. No signs of leaking pipes or roof.

Our next plan of action is to pull the insulation away from the vents in the attic. Most are obstructed — a contractor suggested this some time ago when I pointed out the many nail pops throughout the house.

What else am I missing here? Could there be issues with vapor barrier or siding? Appreciate any insight. Very green here!