Basement Humidity & Crawl Space Humidity
Whenever the outside air is warmer than the inside air, and especially when the outside air is humid, we are likely to have a condensation problem in our basements or crawl spaces. This is because the Relative Humidity of air goes up 2.2% for every one-degree you cool it. Our basements and crawl spaces are always cool because they are below ground. And we know that a house is like a chimney air flows upwards, allowing air to escape the upper levels, with new make-up air being sucked in at the lower levels.

So when it's hot and humid in the summer, rain or not, our basement may be the wettest it has been all year!