Does anyone have any info on what is an “acceptable” level for humidity in a regular house basement? What I am asking on “acceptable” , is how high can the humidity be allowed to get before mold and mildew start to form? House is a two story colonial, built in 1977, poured concrete basement, about 800 sq. ft. , not finished, glass block windows with center screens that I do not open, washer / dryer / work bench / furnace and wood furnace off to one end under family room, sump pump in far corner…standard, solid basement. The guy that sold the house left an old dehumidifier, ( like from 1977 ). Seeing that it was old and having it look like a big energy monster, I would only run it every so often. Well, one yr, un-packing Christmas decorations, quite a few items had mold on them, these were tossed. So, two summers ago I got a new dehumidifier and a small digital temperature / humidity level reader : Temp on top , Humidity on the bottom. Last summer, I was running the dehumidifier on “dry” (there are three settings, normal, dry, and Extra dry” ) Dry is the middle setting. My typical humidity level was around 48% to 55% , basically right around 50%. BUT…..the machine was running ALL THE TIME.. So even with this new dehumidifier, it still added $15 to 20 bucks every month to the electric bill, spring , summer and early fall. This season, 2010 – To save on the electric bill, I have the dehumidifier set on “normal” , it does not run / cycle near as much, but my humidity level is around 60 % to 67% ( 67% is the highest I’ve seen on the digital reader) Basement temperature is about the same, 62, 64, sometimes 68, depending on how hot it is outside. Now ….i understand that all houses are different and everyone’s situation/set up is different, but there has to be some type of baseline to say what is ok, and what is not. Any input (or links for info) is greatly appreciated.