In a previous issue, I wrote about how
to choose foundation systems for
buildings, and why higher R-values
are justified. This month, we'll compare
insulating outside the foundation
wall to insulating inside the wall.
We'll also look at a new system for
placing insulation within a poured
wall.
Outside Insulation Options
The most common exterior insulation
is polystyrene foam either in its
extruded form (Dow blueboard,
Foamular pinkboard, Amoco greenboard,
etc.) or as expanded
polystyrene (EPS), often called beadboard.
The extruded products are
about R-5 per inch thickness, and are
particularly well-suited to underground
applications since they have
relatively high compressive strengths,
and don't take on any appreciable
moisture.
One disadvantage of foam is its cost:
generally four to five times the cost
per R