Conscientious builders strive to conserve
energy, improve quality, and reduce costs, but
few innovative building techniques fulfill all
three objectives. The frost-protected shallow-
footing technique is an exception.
The concept is so basic I'm surprised it
hasn't caught on sooner. Rather than build
the footing below the frost line, you insulate
the ground at the building perimeter to raise
the frost line. If the ground never freezes, you
no longer a deep footing. The technique has
a long history of successful use in the Scandinavian
countries (see "Thirty-Year Track
Record").
With conventional slab construction,
most heat loss occurs at the slab's edge. You
can dramatically reduce heat loss by adding
rigid foam insulation; but with a frost-protected
shallow