I live in the Portland, Oregon area. My home was built in 1993 and has a concrete tile roof. I have many soffitt vents but no venting through the tile roof itself. I have excellent insulation in the attic and a whole house fan mounted in the upstairs hallway. I run the fan minimally in the winter and from 2:00pm to 11:00pm in the summer.
My house was repainted about 5 years ago and starting about 2 years ago the soffitt areas began turning a dark color while the rest of the painted sections looked fine.
I presume the soffitt color is from excess moisture in the attic. Any suggestions? Thanks.

 

I would say you have mole there on the soffitt. A 50 /50 mix of just water and clorox should take it off. Ill bet with that cooler tile roof at night and that fan blowing warm moist air up there is what is doing it. I think you should take a good look up there in the attic . See if its all ok there.
Vents in a home for the attic should be 1/2 in in the soffitt and half out at or near the ridge. A whole house fan is not the way to go anymore in a home If you cant vent it out on its own.

ED