A highway of air leaks runs
through just about every house. It
collects traffic from every interior
wall that holds a pipe or wire. If
interior wall cavities are used as
ducts, it's rush hour whenever the
furnace kicks on. The fast lane is
the space between floor joists
where air travels back and forth to
the outside wall and leaks in and
out around the rim joist.
Blocking the access routes —
every receptacle, pipe, and duct —
may be the only option for
existing homes, though it's tedious
and never totally effective. In new
construction and major remodels,
however, it's worth blocking the
major outlet. By sealing the rim
joist, you avoid the need to seal all
those