Rim Joists can Leak more than Windows.
For many homes, the rim joist is one of the major sources of heat loss and air infiltration.
The rim joist area above the foundation can cause more air leakage into the home than all the windows combined. It is important to also seal and insulate the top of the concrete wall where the sill plate sits.
Rim Joists let in more than just air. Spiders, bugs, and even mice find the rim joist an attractive place to enter the home. The wooden rim or band joist area is where the house's wooden structure rests on the concrete foundation. This area is notorious for gaps and cracks.
Health Issues can Start in the Basement
A house breathes from the basement up. Typically three quarters of the air infiltration comes from the basement. The air entering or exiting the rim joist area can contain high levels of moisture, increasing the likelihood of mold growth and rot in this area. So if there are mold problems in the basement, this can affect the air quality throughout the house