|
Residential Application Example
Thermal performance of AAC Panels
and AAC block is essentially
the same
1.0 Introduction
Building design and material properties
influence thermal performance and energy
consumption for residential and commercial
buildings. AAC wall, floor and roof systems
provide an innovative combination of excellent
thermal conductivity, thermal mass and
low air-infiltration. This practical
combination of properties in one system provides
an excellent thermal insulation material and
permits peak energy usage in the building to be
shifted to off-peak hours, thus reducing
operation cost for building users and owners,
improving comfort of living and reducing the
demand on power generation facilities.
2.0 Definitions.
It is important to remember that thermal
performance of any building material is the
result of several factors and may not be assumed
either effective or ineffective on the basis of
any one factor. In this
section, there are definitions and examples of
the various thermal properties that are used to
determine
overall thermal efficiency of any building
material. It will be shown how these thermal
properties
generally influence the design of the building
envelope and specifically how the AAC thermal
properties
result in outstanding performance and energy
savings. The values for the various AAC thermal
properties are included in a later section of
this chapter.
Thermal Conductivity “K” (Btu.in/h.Ft2.F)
is a measure of the material conductivity as
tested in a laboratory procedure that measures
the heat flow through building material under
steady and constant climatic conditions. It is
important to remember that these laboratory
conditions do not reflect the normal
climatic
cycles. This issue will be discussed in further
detail in the thermal mass section. Based on the
above definition, it is obvious that the
lower the K value the higher the insulating
value. The following table gives the “K” value
for different materials;
|
Designation |
Thermal Conductivity, K (Btu.in/h.Ft2.F) |
|
AAC 32 pcf |
0.96
(1) |
|
Concrete (Density 150 pcf) |
9.98
(2) |
|
Insulation Board (Polystyrene) |
0.2
(3) |
|
Steel |
329 |
|
Water |
4.15 |
(1)
Based on ASTM C51 8
(2)
ASHRAE
(3)
ASHRAE
Thermal
Resistance “R”
(h.Ft2.F/Btu)
is the opposite of the thermal conductivity
and it is
the
resistance of material to conduct or
allow heat flow. R-value
R = (1 / K) x Wall Thickness (in.)
|
Designation |
Thermal Resistance “R” (h.Ft2.F/Btu) |
|
8” AAC 32 pcf Wall System |
10.0 |
|
8” Concrete 150 pcf Wall System |
1.0 |
|
3 ½” Batt Insulation |
13 |
|
1” Steel Plate |
0.003 |
Note: Wall System and
Concrete Wall System Consist of Plaster on
both side of the wall
Heat Transmission Coeficient, U-value
(Btu/h.
Ft2.°F) is defined
as
the
amount of heat, expressed in BTU’s
transmitted in one hour through one square
foot of a building envelope in 1
°F
temperature diference.
U = 1 / R
|
Designation |
U-value (Btu/h.Ft2.F) |
|
8” AAC 32 pcf Wall System |
0.10 |
|
8” Concrete 150 pcf Wall System |
1.0 |
|
3 ½” Batt Insulation |
0.077 |
|
1” Steel Plate |
329 |
Note: AAC Wall System and
Concrete Wall System Consist of Plaster on
both side of the wall
In addition to the
above basic material thermal properties,
other thermal properties such as specific
heat and heat capacity effect the
performance of building envelope.
Specific heat, s (Btu/Ib.°F)
is the amount of heat required to raise one
pound of material one degree
°F.
|
Designation |
Specific heat (Btu/Ib.°F) |
|
8” AAC 32 pcf Wall System |
0.25 |
|
8” Concrete 150 pcf Wall System |
0.21 |
|
3 ½” Batt Insulation |
0.085 |
|
1” Steel Plate |
0.125 |
Heat
capacity, HC
(Btu/Ft2.°F)
or sometimes is referred to as
“thermal
mass”,
is a measure
of how much heat a building component can
store or hold per unit of mass. It is
essentially the specific heat taking in account
the thickness of the material.
|
Designation |
Heat capacity, HC (Btu/Ft2.°F) |
|
8” AAC 32 pcf Wall System |
6.07 |
|
8” Concrete 150 pcf Wall System |
23.0 |
|
3 ½” Batt Insulation |
0.007 |
|
1” Steel Plate |
5.10 |
Note: AAC
Wall System and Concrete Wall System Consist of
Plaster on both sides of the wall
3.0 Understanding the Thermal Mass Benefit
Concept
In the
“steady
state”
thermal
values obtained from laboratory testing, it is
assumed that temperatures at both sides
of a wall are constant and remain constant for a
period of time, unlike what actually occurs in
normal conditions. In actual conditions, the
temperature levels on both sides of walls may
change during a 24-hour period. In many cases,
the exterior temperature may experience large
temperature swings. These changes may cause a
reversal in direction of the heat flow or at the
least, “delay” the heat flow to the point where
it substantially reduces the heat transfer to
the inside the building envelope. The following
diagrams illustrate each of these conditions.
3.1 Reversed Heat
Flow Example - Amarillo, Texas
In Amarillo,
Texas, it is not unusual that the outside day
temperature may fluctuate from 95 °F down to 60
°F in the same 24 hour period while the indoor
temperature is maintained at 75 °F. This drop in
temperature
and the excellent heat capacity of AAC materials
cause a reversal in the direction of heat
transfer back to the outside within the
24 hours. Subsequently, the total heat gain
through the AAC wall system is significantly
less than low thermal mass wall system such as
framed wall. In this case, the combination of
the heat capacity and the excellent thermal
resistance exceeds the performance of a high
“steady state” R-value. T his dynamic
process is known as the “thermal mass
benefit” or “mass-enhanced”
R-value.
3 .2 Delayed Heat
Flow Example – Orlando, Florida
In Orlando, it is not
unusual that when the outside day
temperature is 95 °F, the outside night
temperature will only drop down to 85 °F.
During the same time frame, the inside
temperature could be at 75 °F. In this case,
the drop in the outside temperature may not
be enough to cause a reversal in the
direction of heat transfer. However due to
the wall thickness, its thermal conductivity
(1.1.1) and its heat capacity (1.1.5) a time delay or “Time lag” results
and shifts the peak temperature load to
between 7 to 9 hours later.
Since HVAC systems
are required to be designed for peak loads,
this shift in timing of the peak load can
result in
a significant reduction in the size of
mechanical equipment with a subsequent
reduction in energy consumption and
cost. Table 1.0 shows “Time lag”
values for different building materials.
Table 1.0
shows “Time lag” values for different
building materials.
|
Material |
Time
Lag, hr |
|
8”
AAC Wall |
8 |
|
8”
CMU Wall |
6
(1) |
|
2 x 4
Frame Wall |
2
(1) |
In a previous test, AAC wall surface
temperatures were measured over a 24 hours
period on a west wall, which was painted black to increase surface temperature. The outside
wall temperature fluctuated by as much as 126 F. The inside temperature remained at a pleasant 68
F without air conditioning with a mere 3.6
F variation. Additionally, the peak temperature was
shifted to a later time of the day when energy
is no longer required to mechanically adjust the
indoor temperature.
This “time lag” combined with the heat capacity of
AAC results in substantial reduction of peak
energy
consumption. This reduction is considerable in
residential buildings and represents financial
saving for homeowner in addition to the comfort of living and
pleasant steady interior climate.
4.Dynamic Benefit Analysis
The effectiveness of AAC material in providing
and controlling interior climatic conditions was
illustrated
by testing a wall in conditions that simulate
actual climatic conditions in a comprehensive
energy analysis performed by Oak Ridge National
Laboratory.
In the study performed by ORNL, the steady state
and the dynamic thermal performance of a AAC
wall
system were analyzed using ORNL Building
Technology Center Guarded Hot box. In the
dynamic test
of an 8 ft x 8 ft wall, the climatic boundary
conditions were changed to simulate similar
conditions to normal climatic cycle.
The results of ORNL
steady state and dynamic analysis were used
to develop a model for AAC wall systems
using Department of Energy 2.1 E software.
The computer software was used to simulate
the
heating and cooling loads for a single
family residence with AAC walls compared to
an identical building simulated with
lightweight stud frame wall and a Concrete
Masonry Unit (CMU) wall. Figure 1.0 shows
the house model and the floor plan used in
the study performed by Oak Ridge National
Laboratory for six representative U.S.
climates.
Figure
1.0 - Floor plan of one-story ranch-style
house used in thermal modeling.
Table 2.0 - Simulated heating and cooling energy
required for a ranch house built with AAC
walls as
shown in ORNL report “Whole Wall Rating /
Label for AAC Wall Systems with Solid
Autoclaved Cellular
Concrete Blocks Part II - Dynamic Thermal
Analysis dated February 8, 1999.
|
Location |
Cooling Energy
MBtu] |
Heating Energy
[MBtu] |
Total Energy
[MBtu] |
|
Atlanta |
7.4 |
25.1 |
32.5 |
|
Denver |
1.21 |
48.32 |
49.5 |
|
Miami |
37.36 |
0.65 |
38.01 |
|
Minneapolis |
2.05 |
82.72 |
84.77 |
|
Phoenix |
31.73 |
5.27 |
37.0 |
|
Washington, D.C. |
4.33 |
42.56 |
46.89 |
Additionally, the cooling and heating energy
required for a wood framed house at
different levels of
thermal insulation was calculated to
identify the saving in energy as shown in
table 3.0. It is apparent
that only increasing the R-value of a wall
does not necessarily decrease the required
energy, contrary
to common conception. This can also be
attributed to thermal mass benefit, control
of air infiltration and
construction details.
|
R-value |
Atlanta |
Denver |
Miami |
Minneapolis |
Phoenix |
Washington |
|
|
Annual Cooling Loads [MBtu] |
|
12.5 |
8.98 |
2.72 |
37.42 |
2.94 |
32.68 |
5.65 |
|
15 |
8.53 |
2.48 |
36.61 |
2.77 |
31.51 |
5.29 |
|
20 |
7.93 |
2.14 |
35.85 |
2.47 |
30.20 |
4.83 |
|
29 |
7.41 |
1.83 |
34.86 |
2.18 |
28.62 |
4.39 |
|
37 |
7.42 |
1.92 |
34.58 |
2.20 |
28.36 |
4.41 |
|
|
Annual Heating Loads [MBtu] |
|
12.5 |
25.05 |
48.33 |
0.94 |
80.27 |
7.46 |
41.68 |
|
15 |
23.73 |
45.99 |
0.84 |
77.14 |
6.85 |
39.90 |
|
20 |
22.292 |
43.43 |
0.713 |
73.92 |
6.051 |
37.83 |
|
29 |
20.54 |
40.32 |
0.61 |
69.73 |
5.27 |
35.24 |
|
37 |
20.11 |
39.58 |
0.61 |
68.39 |
5.34 |
34.51 |
Table 3.0 - Simulated heating and
cooling energy required for ranch house
built with the wood framed
walls as shown in ORNL report “Whole Wall
Rating / Label for Wall Systems with Solid
Autoclaved Cellular Concrete Blocks Part II
- Dynamic Thermal Analysis dated February 8,
1999
These
loads were then used to estimate the
effective R-value which would be needed in
ordinary
construction to result in the same total
heating and sensible cooling loads as the
AAC wall system in each of
the six
climates as shown in table 2.0.
The resulting R-value is a steady R-value
for AAC wall multiplied by DBMS (Dynamic
Benefit for Massive Systems). DBMS is
a function of climate, building type and
base envelope system. (i.e., conventional
2x4 wood frame wall system) DBMS (Dynamic
Benefit for Massive Systems) values for the
AAC wall were obtained by comparison between
total loads necessary for heating and
cooling the light-weight wood-frame building
and the AAC unit house for six U.S. climates
and four building orientations. This factor
accounts for not only the steady state
R-value but also the inherent thermal mass
benefit without considering air
infiltration. Figure 2.0 and table 4.0 show
DBMS values and effective R-value for AAC
walls when compared to other wall systems.
|
 |
|
Figure 2.0 - DBMS values for AAC
Walls |
|
|
AAC wall |
Two-core CMU wall |
2x4 Wood Stud Wall |
|
City |
steady- |
DBMS |
Effective |
steady- |
DBMS |
Effective |
Steady- |
DBMS |
Effective |
|
|
state |
|
R-value |
state |
|
R-value |
state |
|
R-value |
|
|
R-value |
|
|
R-value |
|
|
R-value |
|
|
|
Atlanta |
|
1.91 |
15.93 |
|
0.89 |
2.04 |
|
|
|
|
Denver |
|
1.84 |
15.34 |
|
0.91 |
2.08 |
|
|
|
|
Miami |
|
1.62 |
13.51 |
|
0.62 |
1.42 |
|
|
|
|
|
8.34 |
|
|
2.29 |
|
|
12.5 |
1.0 |
12.5 |
|
Minneapolis |
|
1.43 |
11.93 |
|
0.57 |
1.31 |
|
|
|
|
Phoenix |
|
2.53 |
21.10 |
|
1.46 |
3.34 |
|
|
|
|
Washington |
|
1.67 |
13.93 |
|
0.78 |
1.78 |
|
|
|
Table 4.0 - Dynamic thermal performance
characteristics for AAC units, two-core CMU
and wood frame
walls. In
a review of the above charts, AAC wall
outperformed the other wall systems for the
energy consumption by using the lowest
energy demands and showed the highest
effective R-value.
Beyond the thermal properties already
discussed thus far, test of actual buildings
have shown the air infiltration of a
structure to be 63% less than a wood stud
framed structure and 48% less than an
uninsulated 8” CMU wall. The impact of this
on thermal performance and the resulting
whole building annual energy demands of a
building constructed using either AAC walls,
CMU, or and frame walls
were compared using different air-tightness
values. Similar to earlier calculation, six
climates were used
for energy modeling and determination of the
whole building energy demand of buildings
with these different wall systems. Figure
3.0 shows that the increased air-tightness
in houses constructed with AAC wall system
significantly reduces the energy demand
requirements.
Figure 3.0 - Comparison of annual demands
for different wall systems considering
different air-leakage
rates as shown in ORNL report “Whole Wall
Rating / Label for Wall Systems with Solid
Autoclaved Cellular Concrete Blocks Part II
- Dynamic Thermal Analysis dated February 8,
1999.
|
According to the ORNL
report, “the results of computer simulations
for the six U.S. climates show that
annual
energy performance of the single family
residence made of AAC walls is superior in
comparison with a similar house built
using either two-core CMU, steel studs, or
conventional wood-framed walls. On average,
energy demands of the AAC wall house are
about 18%, 36%, and 23% lower than
similar houses constructed with wood
frame walls, two-core CMU, and steel studs
walls, respectively. Chart 1.0 shows
that AAC
wall yielded the least operating energy cost
when compared with other wall systems. In
addition, as a result of lower demand
on peak energy loads, the use of AAC walls
reduces the size of mechanical equipment as
shown in chart 2.0. |
The example cited makes the point that AAC
products can offer the homeowner and the
designer several important benefits if the material’s thermal properties are used
appropriately. To aid in that, this chapter of the Residential Application
Manual provides the information needed by
the design professional to understand and
utilize the properties and design values
that will result in the utmost thermal
efficiency when using AAC.
For the mechanical engineer, included are
simple design tools, tips and general
directions to assist in design of residential projects. All tables and designs aids
were developed by a mechanical engineering consulting firm and are based on
current energy codes such as ASHRAE, Model
Energy Code and State mandated code such as
the Florida Energy Code. Step by step
procedures are available for energy code
compliance, load calculation and equipment
sizing such as Manual J.
5.0 Design Aids – Thermal Properties
for different AAC material
Table 1- Thermal Conductivity (K-value), R-value and U-value
for AAC, Only
|
|
R-Value |
U – Value |
|
AAC
Type |
Density
y
pcf |
Thermal
Conductivity |
|
Thickness, in. |
|
|
Thickness, |
in. |
|
|
6 |
8 |
10 |
12 |
6 |
8 |
10 |
12 |
|
AAC 2.5 (AAC2) |
26 |
0.79 |
7.59 |
10.13 |
12.66 |
15.19 |
0.13 |
0.10 |
0.08 |
0.07 |
|
AAC 2.5 (AAC2) |
32 |
0.96 |
6.25 |
8.33 |
10.42 |
12.50 |
0.16 |
0.12 |
0.10 |
0.08 |
|
AAC 5.0 (AAC5) |
38 |
1.15 |
5.22 |
6.96 |
8.70 |
10.43 |
0.19 |
0.14 |
0.12 |
0.10 |
|
AAC 7.5 (AAC6) |
44 |
1.15 |
5.22 |
6.96 |
8.70 |
10.43 |
0.19 |
0.14 |
0.12 |
0.10 |
Table 2 - Thermal Conductivity (K-value),
R-value and U-Value for AAC, exterior and
interior plaster
|
|
R-Value |
U – Value |
|
AAC
Type |
Densit
y
pcf |
Thermal
Conductivity |
|
Thickness, in. |
|
|
Thickness, |
in. |
|
|
6 |
8 |
10 |
12 |
6 |
8 |
10 |
12 |
|
AAC 2.5 (AAC2) |
26 |
0.79 |
8.91 |
11.45 |
13.98 |
16.51 |
0.11 |
0.09 |
0.07 |
0.06 |
|
AAC 2.5 (AAC2) |
32 |
0.96 |
7.57 |
9.65 |
11.74 |
13.82 |
0.13 |
0.10 |
0.09 |
0.07 |
|
AAC 5.0 (AAC4) |
38 |
1.15 |
6.54 |
8.28 |
10.02 |
11.75 |
0.15 |
0.12 |
0.10 |
0.09 |
|
AAC 7.5(AAC6) |
44 |
1.15 |
6.54 |
8.28 |
10.02 |
11.75 |
0.15 |
0.12 |
0.10 |
0.09 |
•R–value = R
outside air (0.1 7)+ R
ext plaster
(0.3 6)+ R
AAC + R
int plaster(0. 11) +R inside air(0.68)
Table 3 - Thermal
Conductivity (K-value), R-value and U-value
for AAC, brick veneer and interior
plaster
|
|
R-Value |
U – Value |
|
AAC
Type |
Density
pcf |
Thermal
Conductivity |
|
Thickness, in. |
|
|
Thickness, |
in. |
|
|
6 |
8 |
10 |
12 |
6 |
8 |
10 |
12 |
|
AAC 2.5 (AAC2) |
26 |
0.79 |
10.00 |
12.54 |
15.07 |
17.60 |
0.10 |
0.08 |
0.07 |
0.06 |
|
AAC 2.5 (AAC2) |
32 |
0.96 |
8.66 |
10.74 |
12.83 |
14.91 |
0.12 |
0.09 |
0.08 |
0.07 |
|
AAC 5.0 (AAC5) |
38 |
1.15 |
7.63 |
9.37 |
11.11 |
12.84 |
0.13 |
0.11 |
0.09 |
0.08 |
|
AAC 7.5 (AAC6) |
44 |
1.15 |
7.63 |
9.37 |
11.11 |
12.84 |
0.13 |
0.11 |
0.09 |
0.08 |
•
R–value = R
outside air
(0.1 7)+ R
4” brick
(0.44)+ R
Air space 1”
(1 .0) + R
AAC
+ R
int plaster(0.11)+
R
inside air
(0.68)
Table 4 - Thermal Conductivity (K-value),
R-value and U-Value for AAC, exterior
plaster and glued ½”
gypsum board
|
|
R-Value |
U – Value |
|
AAC
Type |
Density
pcf |
Thermal
Conductivity |
|
Thickness, in. |
|
|
Thickness, |
in. |
|
|
6 |
8 |
10 |
12 |
6 |
8 |
10 |
12 |
|
AAC 2.5 (AAC2) |
26 |
0.79 |
9.25 |
11.79 |
14.32 |
16.85 |
0.11 |
0.08 |
0.07 |
0.06 |
|
AAC 2.5 (AAC2) |
32 |
0.96 |
7.91 |
9.99 |
12.08 |
14.16 |
0.13 |
0.10 |
0.08 |
0.07 |
|
AAC 5.0 (AAC5) |
38 |
1.15 |
6.88 |
8.62 |
10.36 |
12.09 |
0.15 |
0.12 |
0.10 |
0.08 |
|
AAC 7.5 (AAC6) |
44 |
1.15 |
6.88 |
8.62 |
10.36 |
12.09 |
0.15 |
0.12 |
0.10 |
0.08 |
R-
value = R outside air
ext plaster
(0.36)+ R
AAC+ R
drywall
inside air(0.68)
Table 5 - Thermal Conductivity (K-value),
R-value and U-Value for AAC, exterior
plaster, furring, and
½” gypsum board
|
|
R-Value |
U – Value |
|
AAC
Type |
Density
pcf |
Thermal
Conductivity |
|
Thickness, in. |
|
|
Thickness, |
in. |
|
|
6 |
8 |
10 |
12 |
6 |
8 |
10 |
12 |
|
AAC 2.5 (AAC2) |
26 |
0.79 |
10.20 |
12.74 |
15.27 |
17.80 |
0.10 |
0.08 |
0.07 |
0.06 |
|
AAC 2.5 (AAC2) |
32 |
0.96 |
8.86 |
10.94 |
13.03 |
15.11 |
0.11 |
0.09 |
0.08 |
0.07 |
|
AAC 5 (AAC5) |
38 |
1.15 |
7.83 |
9.57 |
11.31 |
13.04 |
0.13 |
0.10 |
0.09 |
0.08 |
|
AAC 7.5 (AAC6) |
44 |
1.15 |
7.83 |
9.57 |
11.31 |
13.04 |
0.13 |
0.10 |
0.09 |
0.08 |
R–value = R
outside air (0.17)+ R
ext plaster (0.36)+ R AAC + R
drywall +
furring (1.4) + R
inside air
(0.68)
Table 6 - Specific Heat (s) and Heat
Capacity (HC) for AAC, exterior and
interior plaster
|
|
Heat Capacity |
|
AAC
Type |
Density
pcf |
Specific
Heat |
|
Thickness, in. |
|
|
6 |
8 |
10 |
12 |
|
AAC 2.5 (AAC2) |
26 |
0.25 |
4.00 |
5.08 |
6.17 |
7.25 |
|
AAC 2.5 (AAC2) |
32 |
0.25 |
4.75 |
6.08 |
7.42 |
8.75 |
|
AAC 5.0 (AAC5) |
38 |
0.25 |
5.50 |
7.08 |
8.67 |
10.25 |
|
AAC 7.5 (AAC6) |
44 |
0.25 |
6.25 |
8.08 |
9.92 |
11.75 |
Table 7 - Specific Heat (s) and Heat
Capacity (HC) for AAC, exterior plaster
and ½” drywall
|
|
Heat Capacity |
|
AAC
Type |
Density
pcf |
Specific
Heat |
|
Thickness, in. |
|
|
6 |
8 |
10 |
12 |
|
AAC 2.5 (AAC2) |
26 |
0.25 |
4.28 |
5.36 |
6.45 |
7.53 |
|
AAC 2.5 (AAC2) |
32 |
0.25 |
5.03 |
6.36 |
7.70 |
9.03 |
|
AAC 5.0 (AAC5) |
38 |
0.25 |
5.78 |
7.36 |
8.95 |
10.53 |
|
AAC 7.5 (AAC6) |
44 |
0.25 |
6.63 |
8.36 |
10.20 |
12.03 |
Table 8 - Specific Heat (s) and Heat
Capacity (HC) for AAC, brick veneer and
interior plaster
|
|
Heat Capacity Btu/ft2.F |
|
AAC
Type |
Density
pcf |
Specific
Heat |
|
Thickness, |
in. |
|
|
6 |
8 |
10 |
12 |
|
AAC 2.5 (AAC2) |
26 |
0.25 |
12.51 |
13.59 |
14.68 |
15.76 |
|
AAC 2.5 (AAC2) |
32 |
0.25 |
13.26 |
14.59 |
15.93 |
17.26 |
|
AAC 5.0 (AAC5) |
38 |
0.25 |
14.01 |
15.59 |
17.18 |
18.76 |
|
AAC 2.5 (AAC2) |
44 |
0.25 |
14.76 |
16.59 |
18.43 |
20.26 |
Table 9 - Specific Heat (s) and Heat Capacity
(HC) for AAC, brick veneer and ½” glued drywall
|
|
Heat Capacity Btu/ft2.F |
|
AAC
Type |
Density
pcf |
Specific
Heat |
|
Thickness, |
in. |
|
|
6 |
8 |
10 |
12 |
|
AAC 2.5 (AAC2) |
26 |
0.25 |
12.79 |
13.88 |
14.96 |
16.04 |
|
AAC 2.5 (AAC2) |
32 |
0.25 |
13.54 |
14.88 |
16.21 |
17.54 |
|
AAC 5.0 (AAC5) |
38 |
0.25 |
14.29 |
15.88 |
17.46 |
19.04 |
|
AAC 2.5 (AAC2) |
44 |
0.25 |
15.04 |
16.88 |
18.71 |
20.54 |
Brick 4”
Density = 135 pcf,
Specific heat = 0.20 Btu/lb.
°F
|
