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There is a very real problem with
Some work, and some do not.
Some energy modeling programs
the difference between
a conventionally insulated
They read steady state R-value, and
for thermal mass, but they
do not adjust for
insulated thermal mass.
The real world impact of this is frightening.
In the movement to reduce our carbon
using a faulty energy modeling
have the result of ruling out
cost effective and
energy efficient methods
One example: a couple years ago, NRG
our block to one of the world's
According to their energy models, there
difference between their R-14 wall
(which was a perlite filled 8" cmu)
and the NRG wall.
Their DOE2 based system did not accurately
for insulated thermal mass.
Based on that one bit of misinformation, they
to lose a hundred million dollars over
the next ten years.
For the architect and engineer who may use
programs to compare
mass wall systems, please realize that
the results may not reflect
research produced at Oak Ridge
Lab, which you can find links
to on this site.
To determine if your energy modeling program
you can do a test. Run a
simulation with two R-12 mass walls in
an Arizona climate zone
(where the difference
in thermal performance
should be very
Simulate one wall made up with
2" rigid EPS interior insulation,
and a 10" exterior heavyweight cmu
with partially grouted cores;
the second wall, have an interior portion
with a 6" partially grouted
cmu, with 2" EPS rigid EPS middle layer,
and a 4" partially
cmu as the wall exterior.
If there is no significant difference
between predicted heating and
cooling loads for these walls, then
your energy modeling program
does not accurately differentiate
between isolated (conventional)
and insulated thermal mass walls (NRG).
Take advantage of NRG's on-line,
on-demand course that provides
more detailed information on the topic
of adding energy efficiency
by adjusting the insulation configuration
in mass walls. It includes
and links to, the relevant Oak Ridge
research on the topic.
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