Prioritizing Humidity Control in Basement
Hi! I’m Ken. My 180 year old house in central MA has some sill/beam rot/WDI damage in basement caused by moisture issues. Since I started monitoring the temp & RH in Jan it’s never gone below like 85%. I was thinking of making a negative pressure environment down there with a 2300 cfm box fan in the window to exhaust the humid air – but how do I ensure the make up air is coming from the much drier upstairs air (where there are a couple window air conditioners) and not from the incessantly crazy humid outdoor air?
It’s a walk out basement. The south facing front of the house is the walk out part and has windows to put the fan in. It’s an exposed structural 2 layer of brick wall with many many air leaks. Should I be focusing more on trying to strongly blow air into the basement from upstairs to *positively* pressurize the basement with the upstairs lower humidity a/c air (not the outdoor air leaking in) rather than trying to go the exhaust/negative pressure route and not knowing where my make up air is coming from?? I set the fan up in the window a week ago and while I can feel quite a breeze outside coming from the window and smell the musty basement outside in that air stream, the RH hasn’t budged down. I also put 6mm poly over the ~50% or so of the cellar that’s still dirt w/stone and not yet concrete slabbed. No RH improvement
How important is it to start trying to dry it out before structural work is done (which I must do before fixing the envelope)? I was thinking I’d try to lower the humidity, do a borax clean of everything to try to clear out some mold, then do a BoraCare treatment on everything to kill the termites power post beetles etc. inside the wood. Then get to the structural work. Then the envelope work. But how much do I need to worry about getting it drier now?
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