NRG: The CMU Designed for Today
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About Insulated Thermal Mass:
" The greatest advantages of mass
be obtained when insulation is
on its exterior."
(Advanced Energy Design Guides)
The simple physics behind NRG:
two pieces of concrete separated
expanded polystyrene (EPS).
Concrete has a high heat capacity and a
long thermal lag time, so it can absorb
and store a lot of energy, which it
The continuous EPS barrier minimizes
exterior influence and prevents the
energy inside the building from exiting
through the wall.
Insulated thermal mass minimizes
temperature swings and creates
comfortable living and working space.
Below are excerpts from, and links to,
independent research performed by
experts in the field of building science
and heat transfer.
They reveal the reason that walls with
equal steady state R-values do not always
have equal thermal performance.
They show that steady state R-
not the best measures
of thermal performance.
They confirm that the insulation
of NRG is more
thermally efficient than that
of an ICF (Insulated Concrete Form).
Effects of Different Sequences
of Materials in the
Energy Consumption in Continuously
Used Residential Buildings
Dr. Elisabeth Kossecka* Dr. Jan Kosny**
"Due to the increasing amount of new
exterior building envelope
it is very
optimize the mass and insulation
in walls. In comparing
massive walls with the same
it can be
some wall configurations are
effective than others .
This superior thermal performance can be
detected only for a specific distribution of
mass and insulation inside
Energy effects of different thermal mass
and insulation arrangements
exterior walls, have been studied by several
For multilayer walls, three basic material
configurations were considered:
either inside or outside the massive layer,
and insulation located
between two massive
layers. The results of extensive parametric
have shown explicitly that walls
with the insulation outside always performed
better than those with the insulation inside. "
Thermal Mass - Energy Savings Potential
in Residential Buildings
J. Kosny, T. Petrie, D. Gawin, P. Childs,
A Desjarlais, and J.Christian
Buildings Technology Center, ORNL
"In certain climates, massive building
envelopes-such as masonry,
earth, and insulating concrete forms (ICFs)
-can be utilized
as one of the simplest
ways of reducing building heating and cooling
loads. Very often such savings can be
in the design stage of
the building and on a
relatively low-cost basis. Such reductions in
building envelope heat losses combined with
configuration and the
proper amount of thermal insulation in the
building envelope help to reduce the building
cooling and heating
energy demands and
building related CO2 emission into the atmosphere.
Thermal mass effects occur in buildings
containing walls, floors, and
ceilings made of
logs, heavy masonry, and concrete." "This data
that the most effective wall assemblies
were walls with thermal mass
(concrete) being in
good contact with the interior of the building
(Intmass and CIC).
Walls where the insulation material is
on the interior side (Extmass)
were the worst performing wall assemblies.
Wall configurations with the
core and insulation
both sides of
the wall (ICI)
performed slightly better than Extmass
configurations. However, their performance
was significantly worse
than CIC and
The ICI configuration can be used
analysis of the very
popular Insulated Concrete
since ICF walls
consist of the
between shells made of
Kossecka, E. and Kosny, J. -
“Effect of Insulation and Mass
Exterior Walls on
the Dynamic Thermal
of Whole Buildings”
- DOE, ASHRAE, ORNL Conference -
Thermal Envelopes VII, Clearwater,
FL - Dec. 1998.
Dynamic Thermal Performance and
Energy Benefits of Using
Walls in Residential Buildings
"Utilization of thermal mass in buildings
can be one of the most
effective ways of
reducing building heating and cooling loads.
Several massive modern building envelope
and concrete systems)
have found their application in buildings
in the last decade.
They suffer from the lack of an accepted
of their thermal performance.
The steady-state R-value traditionally
used as a wall thermal performance
measure does not reflect the
thermal performance of massive building
To show the benefit of these systems,
thermal performance analysis
incorporate thermal mass effects.
A new measure of the wall thermal
dynamic performance is proposed
in this paper - Dynamic Benefit for
Massive Systems (DBMS).
thermal mass benefit is a function
of the material configuration and
conditions. DBMS values are obtained by
comparison of the
of the massive walls and light-weight wood
The product of DBMS and steady-
Equivalent for Massive Systems.”
It enables comparisons of
It does not have a physical meaning.
It should be
understood only as an
answer to the question:
'What wall R-value should a house
with wood frame
the same space heating and
cooling loads as a similar
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