Evaluation of Rammed Earth Assemblies as Thermal Mass Through Whole-Building Simulation

Abstract

Rammed earth is a low-carbon and nontoxic alternative to conventional construction materials. It was shown to be beneficial in hot climates, making it prominent for resiliency in the face of climate change. However, rammed earth is not broadly implemented due to its low thermal resistance, even though many studies have elaborated the benefits through its mass, specific heat capacity and hygroscopic properties. This paper presents a comparative thermal simulation of rammed earth and mainstream concrete and wood assemblies, accounting for both heat resistivity and capacity. Rammed earth is shown to provide a steady-state indoor temperature levels while decreasing heating and cooling loads in 20%-52% as opposed to conventional assemblies.

Full text

2020 Building Performance Analysis Conference and
SimBuild co-organized by ASHRAE and IBPSA-USA
EVALUATION OF RAMMED EARTH ASSEMBLIES AS THERMAL MASS
THROUGH WHOLE-BUILDING SIMULATION
Pragya Gupta1, Dana Cupkova1, Lola Ben-Alon1, and Erica Cochran Hameen1
1School of Architecture, Carnegie Mellon University, Pittsburgh, PA
ABSTRACT
Rammed earth is a low-carbon and nontoxic alternative
to conventional construction materials. It was shown to
be beneficial in hot climates, making it prominent for
resiliency in the face of climate change. However,
rammed earth is not broadly implemented due to its low
thermal resistance, even though many studies have
elaborated the benefits through its mass, specific heat
capacity and hygroscopic properties. This paper presents
a comparative thermal simulation of rammed earth and
mainstream concrete and wood assemblies, accounting
for both heat resistivity and capacity. Rammed earth is
shown to provide a steady-state indoor temperature
levels while decreasing heating and cooling loads in
20%-52% as opposed to conventional assemblies.
INTRODUCTION
Buildings contribute to approximately a third of the
world’s final energy use. Space heating and cooling
account for approximately 35% of the total operational
emissions of buildings while another 11% is emitted due
to construction (UN Environmental and International
Energy Agency, 2017) (Perez-Lombard, Ortiz, & Pout,
2008). With such a staggering impact on global energy
consumption and greenhouse gas emissions, it is
imperative that we find solutions that would minimize
the energy requirements over the entire lifecycle of the
building – construction, operation and demolition.
Rammed earth construction was shown to be an
environmentally benign alternative to current
construction materials (Cabeza, et al., 2013). It utilizes
locally sourced materials, requires minimal processing,
and is a healthy, non-toxic material providing enhanced
indoor air quality (Treloar, Owen, & Fay, 2001).
Rammed earth has high density 96.14 lb/ft3 (1,540
kg/m3) and extremely high specific heat capacity 300.94
BTU/lb∙°F (1,260 J/kg∙K) (Hugo & Guillaud, 1984)
(AIRAH, 2000). Combined with low resistivity (CSIRO,
2000) (Taylor & Luther, 2004), rammed earth is ideal for
thermal mass construction and application (Gilly, 1787).
In addition, rammed earth was shown to be especially
beneficial in high diurnal temperature ranges (Hall &
Djerbib, 2006), where it was shown to be able to both
moderate indoor temperatures and shift the peak
temperatures (Minke, 2006). For instance, Soudani, et al.
(2016) show a 6-9-hour time lag in continental climates
and measured a 46-48°F (8-9°C) temperature difference
that considerably reduced the load on mechanical
systems (Soudani, Woloszyn, Fabbri, Morel, & Grillet,
2017). In another study, a 10-hour shift in peak
temperature was measured with about 25% reduction in
amplitude of heat flux on the inner wall surface (Taylor
& Luther, 2004). In a multi-city comparative study in
Egypt, as much as 40% energy savings was reported
when rammed earth was used in place of hollow cement
block in the west wall. The study also found that 12” (30
cm) rammed earth wall was the most optimum thickness
for Egypt (Hatem & Karram, 2016).
Figure 1 Comparison of simulation studies for thermal
mass performance.
Figure 1 summarizes the various simulation studies that
account for thermal mass properties (Ghattas, Ulm, &
Ledwith, 2013) (Ruud, Mitchell, & Klein, 1990)
3°C reduction
in peak indoor
temperature
35
36
37
38
39
40
41
50
60
70
80
90
100
Ghattas et al -
Energy Savings Ruud et al - Peak
Energy Shaving Blondeau et al -
Energy Savings Amos-Aibanyie et
al - Peak Temp
Temperature (°C)
Percentage Energy (%)
Baseline Improvement Baseline Improvement
Up to
4.9%
energy
10% peak
energy
shaving
using pre-
cooled
25% energy
savings
using night
ventilation
© 2020 ASHRAE (www.ashrae.org) and IBPSA-USA (www.ibpsa.us).
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ASHRAE or IBPSA-USA's prior written permission.
618

(Blondeau, Sperandio, & Allard, 1997) and (Amos-
Abanyie & Akuffo, 2013) showing that it can both
reduce the heating and cooling load and contribute in
shifting peak demand.
Another key benefit of rammed earth is its ability to
regulate humidity. It was observed that stabilized
rammed earth walls can maintain relative humidity
levels of 50-60% as compared to painted plasterboard
that results in humidity fluctuation between 40-85%.
This reduces the energy consumption for humidification
and dehumidification (Allinson & Hall, 2010).
While these studies show the significant impacts of
thermal mass on achieving comfort conditions, very few
offer a comprehensive comparison of various
thicknesses of rammed earth, location of insulation
within the assembly and its comparison with mainstream
construction assemblies. Therefore, this study aims to
provide a comparative evaluation of prevalent
construction assemblies and high-performance rammed
earth assembly for additional locations and climate zones
to better address material selection over a range of
climates and cities. Additionally, this study investigates
the impact of rammed earth wall thickness and insulation
location on the annual heating and cooling loads. Lastly,
indoor air temperature profiles and surface temperature
fluctuations are analyzed to compare the performance of
each assembly with respect to the sinusoidal outdoor
temperature variation.
This study is conducted in two phases. In the first phase,
multiple rammed earth assemblies are simulated using a
whole-building simulation to measure the impacts of
earthen thermal mass and the location of the insulation
layer on heating and cooling loads. The highest
performing assembly is then compared to prevalent
construction assemblies – cavity brick construction,
insulated wood frame, and insulated concrete in four
cities: Bishkek (Kyrgyzstan), Jaipur (India), Lanzhou
(China), and Tehran (Iran).
METHODOLOGY AND MODEL
PARAMETERS
The comparative study is performed using an energy
simulation model developed in DesignBuilder v.6
(DesignBuilder, 2019), a graphical user interface for
EnergyPlus (Energy, 2019) simulation engine. The main
aim of the study was to investigate the thermal
performance and energy impacts of earthen mass
construction. To achieve this goal, the study includes the
following steps:
1. Gathering data on rammed earth assemblies including
materials physics and thermal performance.
2. Assessing the climatic conditions of the simulated
locations and their suitability for earthen construction.
3. Investigating the impacts of various rammed earth
wall thicknesses and locations of an additional insulation
layer.
4. Comparison of rammed earth assembly and selected
mainstream construction assemblies with respect to
heating and cooling load profiles.
As shown in Table 1, four different cities were selected
due to their climatic context and traditional use of
earthen materials.
Table 1 Overview of cities selected for simulation
Location
Koppen Climate
classification (Beck,
et al., 2018)
TemperatureRange
Prevalent
traditional earthen
construction
Bishkek,
Kyrgyzstan
Dsa – Hot Summer
Continental Climate
98–10°F (37- -12°C)
Adobe (Uranova &
Begaliev, 2002)
Jaipur,
India
Bsh – Hot Desert
Climate
112–40°F (44-4°C)
Cob, Adobe,
Sandstone
(Rathore, Sharma,
& Preet, 2018)
Lanzhou,
China
Bsk – Semi-Arid
Climate
98 – 0°F (37- -18°C)
Rammed Earth (Li,
et al., 2011)
Tehran,
Iran
Csa – Hot Summer
Mediterranean
Climate
100–24°F (38- -4°C)
Earthen Domes
(Sabzi, 2018)
A typical residential building was modeled with a floor
area of 2,752 ft2 (256 m2) and occupied volume of 16,406
ft3 (465 m3). The building layout was developed as per
the DOE prototype (Kneifel, 2012).
The Finite Difference algorithm that uses fundamental
calculation formation was used rather than the default
conduction transfer method due to its suitability to mass
materials and better heat transfer calculation fidelity
(EnergyPlus, 2019). Fully implicit order based on
Adams-Moulton solution (EnergyPlus, 2019) was
selected as the calculation scheme for Finite Difference
algorithm over the semi-implicit Crank-Nicholson
scheme (EnergyPlus, 2019). In this model, the surface
discretization accounts for the thermal diffusivity of each
material as well as the selected simulation time step rate.
A time step of 30 steps per hour was selected to improve
the calculation accuracy of the algorithm.
Typical Meteorological Year version 3 (TMY30)
weather files (Wilcox & Marion, 2008) were used for
simulating all four cities. The internal heat gains
included occupancy of 4 people. An ideal load profile
was selected for the heating and cooling systems. The
model and occupancy parameters, as detailed in Table 2,
were kept constant with only the external wall assembly
being modified. The various wall assemblies are detailed
in Table 3.
© 2020 ASHRAE (www.ashrae.org) and IBPSA-USA (www.ibpsa.us).
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619

Table 2 Simulation Model Parameters - Constant
Inputs
Parameter
Selection
Number of
Occupants
4
Occupancy
Schedule
NIST Residential Occupancy
Activity
Reading Seated
Metabolic Factor
1.0
Clothing Schedule
Definition
Generic Summer and Winter
Clothing
Calculation Type
Zone Averaged
Environmental Control
Heating Setpoint
68 °F (20 °C) (ASHRAE, 2010)
Cooling Setpoint
76 °F (24 °C) (ASHRAE, 2010)
Minimum Fresh Air
Rate
5.297 ft3/min-person
Mechanical Vent
per Area
0.059 ft3/min-ft2
Construction Assemblies
Below Grade Walls
4 in Brick + 4 in XPS + 4 in CMU
+ 0.5 in Gypsum Plastering
Flat Roof
0.75 in Asphalt + 4 in Fiberboard +
2 in XPS + 4 in Cast Concrete
Pitched Roof
(Occupied)
1 in Clay Tile + 4 in Stone Wool +
0.2 in roofing Felt
Pitched Roof
(Unoccupied)
1 in Clay Tile + 4 in Stone Wool +
0.2 in roofing Felt
Ground Floor
4 in Foam + 4 in Cast Concrete +
2.75 in Screed + 1.2 in Timber
Flooring
External Floor
1 in External Rendering + 4 in
Stone Wool + 0.2 in Timber
Flooring
Airtightness rate
0.3 ac/h, 24/7
Window to Wall
Ratio
15%
Glazing Type
Double Pane Clear Reflective
Glass with 6mm Air Gap
Frame
Aluminum Window Frames (with
thermal break)
Shading
Blinds with highly reflective slats
Control Type
Inside Air Temperature
HVAC Options
HVAC Template
Ideal Loads
Heating System
Gas Furnace, Available 24/7
Cooling System
Air Conditioner, Available 24/7
The internally insulated Rammed Earth assembly was
composed of 4in rammed earth panel followed by 4in
XPS insulation, 4in cavity and 12in rammed earth wall.
The centrally located insulation assembly had 6in
rammed earth wall followed by 4in XPS insulation, 4in
cavity and 10in external rammed earth wall. The external
assembly is listed in Table 3. All three insulated
assemblies had the same thermal conductivity value.
Table 3 Simulation Model Parameters - Variable Inputs
Layer (Interior to
Exterior)
Thickness
(inches)
Conductivity
(BTU/h∙ft∙°F)
Uninsulated Rammed Earth
(URE 12 in)
12 in (30
cm)
0.417 (0.721
W/m-°K)
Uninsulated Rammed Earth
(URE 18 in)
18 in (45
cm)
0.278 (0.481
W/m-°K)
Insulated Rammed Earth
(IRE) – 12 in RE, 4 in
Cavity, 4 in XPS ,4 in RE
24 in (60
cm)
0.045 (0.077
W/m-°K)
Insulated Wood Frame
(IWF) – 0.75 in Stucco,
0.625 in Gypsum Board,
2.6 in R-11 Fiber Glass
Batt Insulation, 4 in Wood
Framing
5.375 in
(13.652
cm)
0.094 (0.163
W/m-°K)
Brick Cavity Construction
(BC) – 4 in Brickwork, 2 in
Cavity, 4 in Brickwork, 0.5
in Plaster
8.500 in
(21.590
cm)
0.275 (0.476
W/m-°K)
Insulated Concrete (IC) – 8
in Concrete, 2.6 in R-11
Fiber Board Insulation, 0.5
in Gypsum Board
11.100 in
(28.194
cm)
0.076 (0.131
W/m-°K)
RESULTS AND DISCUSSION
The results were initially used to investigate the best
rammed earth wall thickness and insulation location that
were then implemented in the comparative analysis with
the conventional assemblies.
Figure 2 Comparison of indoor air temperature for
winter design week for Jaipur, India showing impact of
insulation location and thickness of rammed earth
assemblies
URE 12” – Uninsulated Rammed Earth 12in thick; URE 18”
Uninsulated Rammed Earth 18in thick; IRE E – Semi-externally
Insulated Rammed Earth; IRE I – Internally Insulated Rammed
Earth; IRE M – Rammed Earth with Central Insulation
40
45
50
55
60
65
70
75
24-Dec
24-Dec
24-Dec
25-Dec
25-Dec
25-Dec
26-Dec
26-Dec
27-Dec
27-Dec
27-Dec
28-Dec
28-Dec
28-Dec
29-Dec
29-Dec
30-Dec
30-Dec
30-Dec
Temperature (°F)
Outdoor URE 12" (30cm)
URE 18" (45cm) IRE E (R-11 XPS)
IRE I (R-11 XPS) IRE M (R-11 XPS)
© 2020 ASHRAE (www.ashrae.org) and IBPSA-USA (www.ibpsa.us).
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ASHRAE or IBPSA-USA's prior written permission.
620

Figure 3 Comparison of indoor air temperature for
summer design week for Jaipur, India showing impact
of insulation location and thickness of rammed earth
assemblies
URE 12” – Uninsulated Rammed Earth 12in thick; URE 18”
Uninsulated Rammed Earth 18inthick; IRE E – Semi-externally
Insulated Rammed Earth; IRE I – Internally Insulated Rammed
Earth; IRE M – Rammed Earth with Central Insulation
As seen in Figure 2 and Figure 3, the insulated rammed
earth assemblies outperform the uninsulated assembles
for Jaipur (India). Specifically, the semi-externally
insulated assembly is shown to perform best by both
moderating the temperature fluxes and providing the best
indoor comfort condition.
Specifically, the rammed earth assembly with insulation
located in the center of the wall section provides better
indoor comfort conditions in heating mode, as shown in
Figure 2. Additionally, when moving the insulation layer
to the exterior of the section (indicated as a “semi-
externally insulated rammed earth”), an improved
performance is achieved in a cooling mode, as shown in
Figure 3. This behavior is shown to provide a tradeoff on
an annual basis where the semi-externally insulated
rammed earth assembly results in the lowest annual
heating and cooling loads, as seen in Figure 4. This is
assumingly due to the longer cooling period in hot-arid
climates. An annual heating and cooling loads reduction
of 45% are achieved by adding external insulation to the
12 inch (30 cm) thick uninsulated rammed earth wall.
Overall, the externally insulated assembly resulted in a
6% annual loads reduction, when compared to the
assembly with the insulation in the center of the wall
section (which is the current common practice in the
industry).
Figure 4 Comparison of annual loads for heating and
cooling showing impact of location of insulation within
assembly and thickness of thermal mass.
URE 12” – Uninsulated Rammed Earth 12in thick; URE 18”
Uninsulated Rammed Earth 18in thick; IRE E – Semi-externally
Insulated Rammed Earth; IRE I – Internally Insulated Rammed
Earth; IRE M – Rammed Earth with Central Insulation
Further analysis was carried out using the semi-
externally insulated rammed earth assembly that was
shown to provide the best operational heating and
cooling energy loads performance. The additional
analysis is conducted to compare the semi-externally
insulated rammed earth assembly with conventional
building assemblies for the four selected cities as
mentions in Table 1.
The comparative results are presented using internal
surface temperature fluctuations and indoor air
temperatures. The internal surface fluctuations are
especially useful in isolating the effects of the wall
assemblies’ performance and provide an indicative
insight into the peak moderating and thermal delay
properties of the assemblies.
As seen in Figure 5 and Figure 6, the semi-externally
insulated rammed earth assembly can moderate the
internal temperatures and therefore reduce heating and
cooling consumption when compared to conventional
assemblies. This can be noted more prominently in both
Figure 7 and Figure 8 that show that the average indoor
air temperature fluctuation is only 33% of the outdoor
dry bulb temperature fluctuation in summer and 33% in
winter when using insulated rammed earth. This is
considerable when compared to insulated wood frame
which results in an average flux of 79% compared to
outdoor temperature variation in summer design week
82% for winter design week.
80
85
90
95
100
105
110
7/2/2002
7/2/2002
7/2/2002
7/3/2002
7/3/2002
7/3/2002
7/4/2002
7/4/2002
7/5/2002
7/5/2002
7/5/2002
7/6/2002
7/6/2002
7/6/2002
7/7/2002
7/7/2002
7/8/2002
7/8/2002
7/8/2002
Temperature (
°
F)
Comparison of Summer
Indoor Air Temperature
Outdoor URE 12" (30cm)
URE 18" (45cm) IRE E (R-11 XPS)
IRE I (R-11 XPS) IRE M (R-11 XPS)
0.00
500.00
1000.00
1500.00
2000.00
2500.00
3000.00
3500.00
4000.00
URE
12"
(30cm)
URE
18"
(45cm)
IRE I
(R-11
XPS)
IRE M
(R-11
XPS)
IRE E
(R-11
XPS)
Load (kBtu/hr)
Annual Load Cooling Load Heating Load
© 2020 ASHRAE (www.ashrae.org) and IBPSA-USA (www.ibpsa.us).
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621

Figure 5 Comparison of Indoor Air Temperatures with Outdoor Temperature for Summer Design Week
Figure 6 Comparison of Indoor Air Temperatures with Outdoor Temperature for Winter Design Week
BC – Brick Cavity Wall; IWF – Insulated Wood Frame Assembly; IC – Insulated Concrete Assembly; IRE – Insulated Rammed Earth Assembly
with Semi-external Insulation
As is further evident from the Figure 5 and Figure 6, the
semi-externally insulated rammed earth assembly drives
the internal air temperature closest to the setpoint
comfort conditions, as prescribed by ASHRAE 55-2010
(ASHRAE, 2010) in both summer and winter. For
example, during the summer design week in Jaipur, as
shown in Figure 6, the assembly maintains an average
temperature of 92.9 °F (33.9 °C) with a high of 97.5 °F
(36.4 °C) and minimum of 88.4 °F (31.3 °C) as opposed
to a high of 109 °F (42. 8 °C) and low of 81.0 °F (27.2
°C) on the outside. In comparison, a wood frame
assembly with similar insulation (R-11) drives the indoor
temperature to a high of 105 °F (40.6 °C) and low of 86.0
°F (30.0 °C). This is further illustrated in Figure 9 and
Figure 10. Figure 7 Indoor temperature flux as percentage of
outdoor temperature variation for summer design week
BC – Brick Cavity Wall; IWF – Insulated Wood Frame Assembly; IC
–Insulated Concrete Assembly; IRE – Insulated Rammed Earth
assembly with Semi-external Insulation
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Bishkek Jaipur Lanzhou Tehran
BC (U-0.275
Btu/hr-ft2-°F)
IWF (R-11)
IC (R-11)
IRE (R-11)
1/20/2002
1/20/2002
1/21/2002
1/21/2002
1/22/2002
1/22/2002
1/23/2002
1/23/2002
1/24/2002
1/24/2002
1/25/2002
1/26/2002
1/26/2002
Lanzhou, China
1/13/2002
1/13/2002
1/14/2002
1/14/2002
1/15/2002
1/15/2002
1/16/2002
1/16/2002
1/17/2002
1/17/2002
1/18/2002
1/19/2002
1/19/2002
Tehran, Iran
5
10
15
20
25
30
35
40
45
1/6/2002
1/6/2002
1/7/2002
1/7/2002
1/8/2002
1/8/2002
1/9/2002
1/9/2002
1/10/2002
1/10/2002
1/11/2002
1/12/2002
1/12/2002
Temperature (°F)
Bishkek, Kyrgyzstan
Outdoor
BC (U-
0.275
Btu/hr-
ft2-°F)
IWF (R-
11)
IC (R-11)
IRE (R-
11)
20
30
40
50
60
70
80
12/24/2002
12/24/2002
12/25/2002
12/25/2002
12/26/2002
12/26/2002
12/27/2002
12/27/2002
12/28/2002
12/28/2002
12/29/2002
12/29/2002
12/30/2002
12/30/2002
Temperature (°F)
Jaipur, India
7/27/2002
7/27/2002
7/28/2002
7/28/2002
7/29/2002
7/29/2002
7/30/2002
7/31/2002
7/31/2002
8/1/2002
8/1/2002
8/2/2002
Lanzhou, China
7/27/2002
7/27/2002
7/28/2002
7/28/2002
7/29/2002
7/29/2002
7/30/2002
7/31/2002
7/31/2002
8/1/2002
8/1/2002
8/2/2002
Tehran, Iran
60
65
70
75
80
85
90
95
100
105
110
7/27/…
7/27/…
7/28/…
7/29/…
7/29/…
7/30/…
7/31/…
8/1/2…
8/1/2…
8/2/2…
Temperature (°F)
Bishkek, Kyrgyzstan
Outdoor
BC (U-0.275
Btu/hr-ft2-°F)
IWF (R-11)
IC (R-11)
IRE (R-11)
7/27/2002
7/27/2002
7/28/2002
7/28/2002
7/29/2002
7/29/2002
7/30/2002
7/31/2002
7/31/2002
8/1/2002
8/1/2002
8/2/2002
Jaipur, India
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ASHRAE or IBPSA-USA's prior written permission.
622

Figure 8 Indoor temperature flux as percentage of
outdoor temperature variation for winter design week
BC – Brick Cavity Wall; IWF – Insulated Wood Frame Assembly; IC
–Insulated Concrete Assembly; IRE – Insulated Rammed Earth
assembly with Semi-external Insulation
Figure 9 Comparison of indoor air temperature
extremes with comfort conditions for summer design
week for Jaipur
BC – Brick Cavity Wall; IWF – Insulated Wood Frame Assembly; IC
–Insulated Concrete Assembly; IRE – Insulated Rammed Earth
assembly with Semi-external Insulation
Figure 10 Comparison of indoor air temperature
extremes with comfort conditions for winter design
week in Jaipur, India
BC – Brick Cavity Wall; IWF – Insulated Wood Frame Assembly; IC
–Insulated Concrete Assembly; IRE – Insulated Rammed Earth
assembly with Semi-external Insulation
Figure 11 Comparison of indoor air temperature
extremes with comfort conditFions for winter design
week in Tehran, Iran
BC – Brick Cavity Wall; IWF – Insulated Wood Frame Assembly; IC
–Insulated Concrete Assembly; IRE – Insulated Rammed Earth
assembly with Semi-external Insulation
As shown in Figure 11., in the milder climate represented
by Tehran, the insulated wood frame achieves the
highest temperature level in winter but also reaches as
low as 35.5 °F (1.9 °C). The average indoor temperature
with insulated wood frame is 43.6 °F (6.5 °C) while for
insulated rammed earth, it is 45.6 °F (7.5 °C) therefore
providing higher thermal comfort.
A comparison of the internal surface temperature
fluctuations was assessed in order to analyze the heat
transfer through the wall assemblies. It was found that
the brick cavity construction and insulated rammed earth
have the lowest temperature fluctuations on the internal
surface. This helps in moderating the indoor air
temperature thereby maintaining the highest radiant
comfort.
Figure 12 Comparison of Inside Surface Temperature
Fluctuation with Outdoor Temperature Fluctuation for
Summer Design Week in Bishkek, Kyrgyzstan
BC – Brick Cavity Wall; IWF – Insulated Wood Frame Assembly; IC
–Insulated Concrete Assembly; IRE – Insulated Rammed Earth
assembly with Semi-external Insulation
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Bishkek Jaipur Lanzhou Tehran
BC (U-0.275
Btu/hr-ft2-°F)
IWF (R-11)
IC (R-11)
IRE (R-11)
0.00
20.00
40.00
60.00
80.00
100.00
Temperature (°F)
Average
max indoor
temp
Average
min indoor
temp
Cooling
setback
Cooling
setpoint
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
Temperature (°F)
Average
max
indoor
temp
Average
min
indoor
temp
Heating
setpoint
Heating
setback
0.00
20.00
40.00
60.00
Outdoor BC IWF (R-
11) IC (R-
11) IRE (R-
11)
Temperature (°F)
Average max indoor temp Average min indoor temp
Heating setpoint Heating setback
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
27-Jul
28-Jul
29-Jul
30-Jul
31-Jul
1-Aug
2-Aug
Temperature (°F)
Outdoor BC IWF
IC IRE
© 2020 ASHRAE (www.ashrae.org) and IBPSA-USA (www.ibpsa.us).
For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without
ASHRAE or IBPSA-USA's prior written permission.
623

Figure 13 Comparison of Inside Surface Temperature
Fluctuation with Outdoor Temperature Fluctuation for
Winter Design Week in Bishkek, Kyrgyzstan
BC – Brick Cavity Wall, IWF – Insulated Wood Frame Assembly; IC
–Insulated Concrete Assembly; IRE – Insulated Rammed Earth;
Assembly with Semi-external Insulation
A similar trend of reduced temperature fluctuations by
the rammed earth assembly is seen for all cities, as
shown in Figure 12 and Figure 13. The temperature flux
on the inside surface is an average of 7.3 °F (4.0 °C) in
the summer design week and 1.3 °F (0.7 °C) in winter
design week for insulated rammed earth assembly as
compared to an average of 17.9 °F (9.9 °C) and 16.8 °F
(9.3 °C) respectively for insulated wood frame. Overall,
an average of 20% reduction was observed in insulated
rammed earth construction as compared to insulated
concrete walls. Furthermore, Figure 12 shows that the
insulated wood frame assembly has the highest heat
transfer within the assembly with internal surface
temperatures closely following the outdoor temperature
variation. This is further reflected in the annual heating
and cooling load calculation shown in Figure 14.
Figure 14 Comparison of annual heating and cooling
load for all four assemblies for the simulated cities
BC – Brick Cavity Wall; IWF – Insulated Wood Frame Assembly; IC
–Insulated Concrete Assembly; IRE – Insulated Rammed Earth
assembly with Semi-external Insulation
CONCLUSION
Rammed earth is a low-carbon, minimally processed,
and nontoxic alternative to prevalent construction
materials such as concrete and insulated timber frame.
The objective of the study was to investigate the
comparative performance of rammed earth assembly as
opposed to mainstream construction and the optimum
location of insulation. Using dynamic whole-building
simulations in hot-arid climates, this study accounts for
not only thermal resistance but also the specific heat
capacity and therefore testing the implications of both
insulation and thermal mass on heating and cooling
loads. The results of this study show that insulated
rammed earth walls are better suited for hot arid climates
than uninsulated rammed earth. It was found that adding
insulation to rammed earth wall can reduce the heating
and cooling load by 45%. Compared to the common
practice of adding insulation in the middle, shifting it
towards the exterior can result in an additional 6%
reduction.
When compared to conventional assemblies – cavity
brick construction, insulated wood frame, and insulated
concrete, semi-externally insulated rammed earth
outperformed the conventional assemblies in terms of
heating and cooling loads reductions, while providing
steady indoor comfort temperature levels. Rammed earth
assembly had the least inside surface temperature
fluctuations, providing an even moderation of indoor air
temperature.
When compared to concrete, an average reduction of
18% in annual heating load and 24% in annual cooling
load was observed across all modeled cities.
Significantly, insulated rammed earth assemblies were
shown to reduce residential heating and cooling loads by
20% when compared to insulated concrete walls. These
results confirm that in regions with high diurnal
variation, thermal mass assemblies can provide better
indoor environmental quality through temperature
modulation.
While this study compares mainstream assemblies with
varied thicknesses, construction costs, and thermal
properties, future research should provide an extended
systematic comparison while keeping constant thermal
and costs constraints. Additionally, a next phase
simulation should include the effects of hygrothermal
properties in the calculation in order to investigate the
impacts of indoor humidity levels.
0.00
5.00
10.00
15.00
20.00
25.00
6-Jan
7-Jan
8-Jan
9-Jan
10-Jan
11-Jan
12-Jan
Temperature (°F)
Outdoor BC IWF
IC IRE
0.00
1000.00
2000.00
3000.00
4000.00
5000.00
Lanzhou Bishkek Tehran Jaipur
Load (kBtu/hr)
BC IWF IC IRE
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REFERENCES
Allinson, D., & Hall, M. (2010). Hygrothermal analysis of a
stabilised rammed earth test building in the UK.
Energy and Buildings, 854-852.
Amos-Abanyie, S., & Akuffo, F. K.-S. (2013). Effects of
Thermal Mass, Window Size, and Night-Time
Ventilation on Peak Indoor Air Temperature in the
Warm-Humid Climate of Ghana. The Scientific
World.
ASHRAE. (2010). ANSI/ASHRAE/IES Standard 55-2010:
Energy Standard for Buildings except Low-Rise.
Atlanta.
Beck, H., Zimmermann, N., McVicar, T., Vergopolan, N.,
Berg, A., & Wood, E. (2018). Present and future
Köppen-Geiger climate classification maps at 1-km
resolution. Sci Data. doi:10.1038/sdata.2018.214,
5:180214
Beckett, C., Cardell-Oliver, R., Ciancio, D., & Huebner, C.
(2017). Measured and simulated thermal behaviour
in rammed earth houses in a hot-arid climate. Part
B: Comfort. Journal of Building Energy, 146-158.
Blondeau, p., Sperandio, M., & Allard, F. (1997). Night
ventilation for building cooling in summer. Solar
Energy, 327-335.
Cabeza, L. F., Barreneche, C., Miro, L., Morera, J. M.,
Bartoli, E., & Fernandez, A. (2013). Low carbon
and low embodied energy materials in buildings: A
review. Renewable and Sustainable Energy
Reviews, 536-542.
CSIRO. (2000). Mud walls give poor insulation: CSIRO.
Retrieved from www.dbce.csiro.au/inno-
web/0600/mud-walls.htm
DesignBuilder. (2019). DesignBuilder Simulation Version
6.1.2.9.
Dong, X., Soebarto, V., & Griffith, M. (2014). Achieving
thermal comfort in naturally ventilated rammed
earth houses. Building and Environment, 588-598.
Energy, U. D. (2019). EnergyPlus Version 9.2.0.
EnergyPlus. (n.d.). Engineering Reference - The Reference to
EnergyPlus Calculations. Retrieved 02 2019, from
EnergyPlus:
https://energyplus.net/sites/default/files/pdfs_v8.3.0
/EngineeringReference.pdf
Fodde, E. (2009). Traditional Earthen Building Techniques in
Central Asia. International Journal of
Architectural, 145-168.
Ghattas, R., Ulm, F.-J., & Ledwith, A. (2013). mapping
thermal mass benefit. Concrete sustainability hub.
Gilly, D. (1787). Handbuch der Land-Bau-Kunst: vorzüglich
in Rücksicht auf die Construction der Wohn- und
Wirthschafts-Gebäude für angehende Kameral-
Baumeister u. Ökonomen. Braunschweig and Halle.
Hall, M., & Djerbib, Y. (2006). Moisture ingress in rammed
earth:Part 3 – Sorptivity, surface receptiveness and
surface inflow velocity. Construction and Building
Materials, 384–395.
Hugo, H., & Guillaud, H. (1984). Earth Construction Primer.
Craterre, 8.
Kneifel, J. (2012). Prototype Residential Building Designs for
Energy and Sustainability Assessment. National
Institute of Standards and Technology.
Li, Z., Wang, X., Sun, M., Chen, W., Guo, Q., & Zhang, H.
(2011). Conservation of Jiaohe ancient earthen site
in China. Journal of Rock Mechanics and
Geotechnical Engineering, 270-281.
Minke, G. (2006). Building with Earth: Design and
Technology of a Sustainable Architecture. Basel:
Birkhäuser.
Perez-Lombard, L., Ortiz, J., & Pout, C. (2008). A review on
buildings energy consumption information. Energy
and Buildings, 394-398.
Rathore, M., Sharma, S. K., & Preet, V. (2018). Analysis of
Traditional and Existing Construction Practices for
Sustainable Rural Houses in the Southern Western
Part of Rajasthan. International Journal of
Engineering Research & Technology.
Rubel, F., & Kottek, M. (2004). Observed and projected
climate shifts 1901–2100 depicted by world maps
of the Koppen-Geiger climate classification.
Meteorologische Zeitschrif, 135-141.
Ruud, M., Mitchell, J., & Klein, S. (1990). Use of builsing
thermal mass to offset cooling loads. ASHRAE
Transactions.
Sabzi, M. Z. (2018). Survey and Analysis of Various Domes
in the Structure of Traditional Iranian Buildings.
Kerpic’18 – Back to Earthen Architecture:
Industrialized, Injected, Rammed, Stabilized, 305-
312.
Soudani, L., Woloszyn, M., Fabbri, A., Morel, J.-C., &
Grillet, A. (2017). Energy evaluation of rammed
earth walls using long term in-situ measurements.
Solar Energy, 70–80.
doi:10.1016/j.solener.2016.11.002
Taylor, P., & Luther, M. (2004). Evaluating rammed earth
walls: a case study. Solar Energy, 79-84.
Treloar, G. J., Owen, C., & Fay, R. (2001). Environmental
assessment of rammed earth construction systems.
Structural Survey, 99-106.
UN Environmental amnd International Energy Agency.
(2017). Towards a zero-emission, efficient, and
resilient buildings and construction sector. Global
Status Report 2017.
Uranova, S., & Begaliev, U. T. (2002). World Housing
Encyclopedia: an Encyclopedia of Housing
Construction in Seismically Active Areas of the
World. Earthquake Engineering Research Institute;
International Association for Earthquake
Engineering.
Wilcox, S., & Marion, W. (2008). Innovation for Our Energy
Future Users Manual for TMY3 Data Sets.
Retrieved from http://www.osti.gov/bridge
© 2020 ASHRAE (www.ashrae.org) and IBPSA-USA (www.ibpsa.us).
For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without
ASHRAE or IBPSA-USA's prior written permission.
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