humidity in unfinished space
Moved into a 2-story house on a slope. It has an unfinished room on the lower floor that I want to use as a workshop. On the uphill side, the room is below-grade and has a raw concrete retaining wall (typical basement wall). Floor is concrete slab. The wall on the downslope side has timber framing like a normal house room (but open to the inside, eg. no interior sheetrock). Exterior appears to be wood siding with I assume latex paint. No HVAC right now in this space, and humidity inside is same as outside, it hovers around 65% which I worry may promote rust and mildew for anything inside. I will get a dehumidifier for this space (520 sq.ft), but to reduce power use, I don't want to run it 24/7. Will sealing the concrete wall & floor help? Both appear clean and dry and I don't see any sign of past water leaks. Would a moisture barrier on the timber framed wall be a good idea, or just trap moisture inside the wall and cause more trouble?
After reading up on this, it seems any use of simple plastic sheeting as a moisture barrier can cause condensation and rot inside the wall, anywhere that the outdoor temp. is sometimes warmer and sometimes cooler than indoor. Looks like I want something "breathable", eg. slow down air movement, but not completely stop water vapor diffusion.