We have all heard claims that the
"effective" R-value of walls insulated
with fiberglass batts may be drastically
reduced by installation defects such as
gaps, voids, compression, etc. I've seen
advertising brochures, for example,
that state the "effective" R-value of an
installed R-19 fiberglass batt may
actually be as low as R-8. Like many
such assertions, the brochure claimed
there was government research data to
support its statements.
How real are those claims? Is it possible
that installation defects can
cause a 50% or 60% reduction in wall
R-value? And are there really research
studies that prove it? When your insulation
contractor smilingly stuffs that
fluffy 6-inch batt into wall cavities,
are you getting an R-19 wall or an