what humidity level for basement
Shares & Saves. Save. The ideal moisture level for a basement, whether finished or unfinished, is 30 to 50 percent relative humidity. During summertime, outside moisture pours in through basement walls and windows, bumping this figure up to 65 to 70 percent in much of the United States and Canada.hares & Saves. Save. The ideal moisture level for a basement, whether finished or unfinished, is 30 to 50 percent relative humidity. During summertime, outside moisture pours in through basement walls and windows, bumping this figure up to 65 to 70 percent in much of the United States and Canada.