Beginning this year, many namebrand
windows will have lower Rvalue
ratings. Eight window manufacturers
—Andersen, Marvin,
Pella, Louisiana-Pacific, BuiltBest,
Norco, Sealrite, and Sembling-
Mink—have adopted a new
method of calculating R-values
which will result in lower numbers.
But the windows have not
changed, only the calculations.
The eight companies who
have adopted the new method are
all members of the National
Wood Window and Door Association
(NWWDA). According to
Jim Benney, manager of technical
services and spokesman for the
NWWDA, the members elected
to adopt the new method "so buyers
would have a fair basis of comparison."
The decision was initiated
by a change in the 1989
ASHRAE Handbook which
includes the new method in their
procedures. NWWDA expects all
window manufacturers to follow
suit eventually.
The new