energies
Article
Thermal Characterization of Recycled Materials for
Building Insulation
Arnas Majumder 1 , Laura Canale 2 , Costantino Carlo Mastino 3 , Antonio Pacitto 2 , Andrea Frattolillo 3
and Marco Dell’Isola 2, *
1
2
3
*
Citation: Majumder, A.; Canale, L.;
Mastino, C.C.; Pacitto, A.; Frattolillo,
A.; Dell’Isola, M. Thermal
Characterization of Recycled
Materials for Building Insulation.
Energies 2021, 14, 3564. https://
doi.org/10.3390/en14123564
Academic Editors: Ravi
Anant Kishore and Marcus Bianchi
Received: 17 May 2021
Accepted: 9 June 2021
Published: 15 June 2021
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
Department of Civil Engineering, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Italy;
amajumder@unisa.it
Department of Civil and Mechanical Engineering, University of Cassino and South Lazio, 03043 Cassino,
Italy; l.canale@unicas.it (L.C.); alpacitto@unicas.it (A.P.)
Department of Civil and Environmental Engineering, University of Cagliari, 09123 Cagliari, Italy;
costantino.mastino@fisicatecnica-unica.it (C.C.M.); andrea.frattolillo@unica.it (A.F.)
Correspondence: dellisola@unicas.it
Abstract: The building sector is known to have a significant environmental impact, considering
that it is the largest contributor to global greenhouse gas emissions of around 36% and is also
responsible for about 40% of global energy consumption. Of this, about 50% takes place during the
building operational phase, while around 10–20% is consumed in materials manufacturing, transport
and building construction, maintenance, and demolition. Increasing the necessity of reducing the
environmental impact of buildings has led to enhancing not only the thermal performances of
building materials, but also the environmental sustainability of their production chains and waste
prevention. As a consequence, novel thermo-insulating building materials or products have been
developed by using both locally produced natural and waste/recycled materials that are able to
provide good thermal performances while also having a lower environmental impact. In this context,
the aim of this work is to provide a detailed analysis for the thermal characterization of recycled
materials for building insulation. To this end, the thermal behavior of different materials representing
industrial residual or wastes collected or recycled using Sardinian zero-km locally available raw
materials was investigated, namely: (1) plasters with recycled materials; (2) plasters with natural
fibers; and (3) building insulation materials with natural fibers. Results indicate that the investigated
materials were able to improve not only the energy performances but also the environmental comfort
in both new and in existing buildings. In particular, plasters and mortars with recycled materials
and with natural fibers showed, respectively, values of thermal conductivity (at 20 ◦ C) lower than
0.475 and 0.272 W/(m·K), while that of building materials with natural fibers was always lower than
0.162 W/(m·K) with lower values for compounds with recycled materials (0.107 W/(m·K)). Further
developments are underway to analyze the mechanical properties of these materials.
Keywords: thermal conductivity; recycled building materials; building insulation materials; sustainable building materials; sustainability; circular economy
published maps and institutional affiliations.
1. Introduction
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
In the past few years, in both developed and developing countries, there is growing
attention to the concepts of sustainability and energy-saving. This constant and increasing
awareness is due to the fact that several issues like global warming, natural resources
depletion, deforestation, and ozone layer depletion are threatening the livability and
existence of the majority of species on earth [1,2]. In light of these vulnerabilities, it is
quite clear that to preserve the global environment and the planet itself, crucial urgent
interventions are needed. To enable global pollution mitigation, decisions have to be
taken into account including several aspects such as lifestyle changes, energy consumption
patterns, resource distribution, and energy efficiency production [1,3]. It is well known that
Energies 2021, 14, 3564. https://doi.org/10.3390/en14123564
https://www.mdpi.com/journal/energies
Energies 2021, 14, 3564
2 of 16
the building sector is the largest contributor to global greenhouse gas (GHG) emissions
(around 36% in the European Union) [4–6], of which over 80% take place during the
building operational phase [7]. Furthermore, the building sector is responsible for about
40% of global energy consumption and the major part (about 50%) is principally due
to residential and commercial buildings meeting various energy needs such as heating,
ventilation, air conditioning (HVAC), and water heating [8]. A smaller percentage, around
10–20%, of energy is consumed in other activities such as (i) the manufacturing of building
materials; (ii) transport of building materials from production plants to building sites;
(iii) construction of the building; (iv) operation of the facilities (“operational” energy); and
(v) end-life demolition activities [9,10].
In light of this, the European Union (EU) has already committed itself to strongly
reducing the energy consumption of new and existing buildings [11]. Among all possible actions, the insulation of new and existing buildings plays a key role, since it is well
known that good thermal insulation of the building could lead to saving about 65% of the
energy consumption [12–15]. As highlighted in [16,17], most of the insulating materials
are made mainly from natural and man-made synthetic (organic and inorganic) fibers and
several studies have investigated the thermo-physical properties of such materials. Their
“best” thermal conductivity was found to range from 0.015 W/(m·K) for aerogel panels
to 0.100 W/(m·K) for recycled rubbers, as also shown in [18] and [19]. On the other hand,
in recent years, increasing attention has been paid not only to energy efficiency, but also
to the ecological and environmental impacts and overall sustainability of buildings and
building materials. Indeed, recently, the EU introduced the Renovation Wave Strategy
(RWS) with the objective to improve the energy performance of buildings through higher
energy and resource efficiency, which is to be achieved by doubling the renovation rate in
the next 10 years [20]. Among the lead actions, the RWS emphasizes the need to expand the
market for sustainable construction products and services including the integration of new
materials and nature-based solutions, material reuse, and recovery targets. Thus, major
attention is being given not only to shifting from synthetic materials to natural/biological
ones [1], but also to exploiting the use of waste and recycled materials for insulation purposes. Among the latter, recycled glass fiber, recycled PET, asphalt mixtures with recycled
materials [21,22], recycled rubber, and recycled textile fiber (e.g., jute fiber recovered from
old jute bags [23]) have been investigated in different studies, showing that their thermal
conductivity is quite in line with one or the other above-mentioned materials, varying from
0.031 to 0.140 W/(m·K). Considering conventional insulating materials (e.g., synthetic,
sheep wool, glass wood, cellulose, hemp, jute etc.) or uncommon ones (e.g., recycled
glass fiber, recycled PET, recycled textile etc.), these are sold in panel format or in rolls
for installation [24]. These formats can present some technical difficulties in their implementation such as encumbrance, because the insulation is applied externally as a separate
layer to the load-bearing structure, and then buffered on the outside with an additional
brick lining. Thus, there is growing interest in novel building/insulating materials made
by mixing materials of biological origin (e.g., hemp, date palm fiber, oil palm fiber, cork,
etc.) or recycled waste materials (e.g., recycled PET) with typical binding materials (e.g.,
lime, cement, clay, etc.), which would allow insulating plasters with easy applicability and
reduced encumbrance to be obtained. In this context, El Azhary et al. [25] mixed straw at
various proportions with clay and studied the thermal properties of the resulting material;
Benmansour et al. [26] investigated the mortar’s thermo-mechanical behavior (cement and
sand at various proportions) reinforced with two different sizes and mixtures of date palm
fibers. Hempcrete (lime and hemp concrete) was manufactured by Elfordy et al. [27] and
the thermo-mechanical properties of the same were evaluated. Valenza et al. [28] created a
cement matrix by using washed and un-washed Sicilian sheep wool (waste product) cut
into three different sizes and percentage and studied the samples’ thermal insulation and
mechanical properties. As mentioned in Raut and Gomez [29], in Malaysia, oil palm waste
is recognized as a problem for the local environment; therefore, the authors evaluated the
possibility of using industrial residuals like oil palm and fly ash as a binder along with
Energies 2021, 14, 3564
3 of 16
cement and oil palm fiber as a reinforcing material. The applicability of jute fiber mainly
focused on its use for reinforced concrete, as shown in Zakaria et al. [30]. The application
of jute fiber is shown in Ferrandez-García et al. [23], where the fibers were recovered from
end-life transportation jute bags to prepare thermo-mechanical panels. An interesting solution, not only from a thermophysical point of view, but also from the eco-sustainability one,
is lightweight concrete with recycled-PET aggregates (recycled polyethene terephthalate)
for which a thermal conductivity of 0.034 W/(m·K) was found in [31–34].
In this context, it is clear that both recycled and natural materials, derived from local
industrial and/or agricultural wastes, could play a major role in the construction sector,
being able not only to provide good energy performances if integrated into traditional
building materials, but also meeting the need for eco-sustainability and waste minimization.
Their impact could be even higher in isolated regions and islands, taking on an even more
significant economic value. This study falls under the regional project PLES (Local Products
for Sustainable Construction) of the region of Sardinia (Central Italy), whose main goal is
to promote the local construction market and help make it self-sufficient in terms of newer,
innovative, and sustainable building materials. The aim of this work was to provide a
detailed analysis for the thermal characterization of locally sourced (i.e., at 0-km) recycled
materials for building insulation. To this end, the thermal behavior of different materials
representing industrial residual or wastes, collected or recycled using Sardinian zero-km
locally available raw materials, was investigated, namely: (i) plaster with natural fibers; (ii)
plasters with recycled materials; and (iii) thermo-insulating building materials with natural
fibers. As a further insight, in order to estimate the possible energy savings obtainable
with the use of the above-mentioned materials replacing traditional plasters, a numerical
simulation was carried out on a case-study building in different scenarios, for different
climatic conditions and for different reference stratigraphies: a typical building built in
the 1980s and those whose elements (e.g., plaster, brickwork, thermal insulation) offer the
maximum allowed U-values, according to local regulations.
2. Materials and Methods
2.1. Sample Materials
The materials investigated within this paper were obtained by mixing typical binding
materials of the Sardinian subsoil, specifically lime putty, opus signum, and raw clay, and
insulating materials represented by natural waste products or agricultural by-products
normally destined for landfill. A total of twelve nature-based thermal insulation specimens
were realized using different binding as well as insulating materials and using sand (3 µm
diameter) as the aggregate (Table 1).
Table 1. Ingredients involved in the samples’ realization.
Binding Elements
Lime
Opus signinum
Clay
Aggregating Material
Sand
Strengthening and Insulating Materials
Sheep wool fibre
Thistle fibre
Hemp shives
Jute fibre
3 cm (±2 mm) long
1 cm (±2 mm) long
1 cm (±2 mm) long
1 cm (±2 mm) long
Referring to Table 1, the wool fibers were collected from mattress stuffing, couches,
and chairs padding. The fibers were washed, dried and sanitized to remove the impurities
and finally manually cut to obtain the desired length. The hemp shives were collected
and pealed directly from the hemp stalks, not processed or combed. They represent a
huge production of agricultural waste that, according to current legislation, should be
disposed of in landfills or incinerators. The jute fiber was collected from recycled jute bags,
traditionally used to carry and store potatoes, cereals, coffee, etc. The broken bags were
chopped into small pieces and later washed to remove the dust, treated, and combed to
make the fiber suitable for the preparation of samples. The opus signinum was obtained
from crushed tiles, no longer usable for their primary covering function, and which would
Energies 2021, 14, x FOR PEER REVIEW
Energies 2021, 14, x FOR PEER REVIEW
Energies 2021, 14, x FOR PEER REVIEW
4 of 16
4 of 16
4 of 16
of in landfills or incinerators. The jute fiber was collected from recycled jute bags, tradi4 of 16
to carry and store potatoes, cereals, coffee, etc. The broken
bags were
44 of
or incinerators. The jute fiber was collected from recycled jute
bags, tradiof 16
16
chopped
into small
pieces andThe
later
washed
to remove
thefrom
dust,recycled
treated,jute
and
combed
to4 of 16
of in landfills
or incinerators.
jute
fiber was
collected
bags,
tradiEnergies 2021, 14, 3564
tionally
used or
to incinerators.
carry and store
potatoes,
cereals,
coffee,
etc.recycled
The broken
bags tradiwere
of
in
landfills
The
jute
fiber
was
collected
from
jute
bags,
make
the
fiber
suitable
for
the
preparation
of
samples.
The
opus
signinum
was
obtained
tionally
used to
carry and The
storejutepotatoes,
cereals, from
coffee,
etc. The
broken
were
of in landfills
or incinerators.
fiber
was collected
recycled
jute
bags,
tradi-bags
chopped
into small
pieces
and
later
washed
to remove
the
dust,
treated,
and
combed
to
tionally
used
to
carry
andand
store
potatoes,
cereals,
coffee,
etc.
The
broken
bagswould
were
from
crushed
tiles,
no
longer
usable
for
their
primary
covering
function,
and
which
chopped
into
small
pieces
later
washed
to
remove
the
dust,
treated,
and
combed
to
of
in
landfills
or
incinerators.
The
jute
fiber
was
collected
from
recycled
jute
bags,
traditionally
used
to
carry
and
store
potatoes,
cereals,
coffee,
etc.
The
broken
bags
were
of in
landfills
or incinerators.
The
jute fiber wasofcollected
from
recycled
jute bags, tradimake
the
fiber
suitable
for
the
preparation
samples.
The
opus
signinum
was
obtained
chopped
small
pieces
and
later
washed
tosamples.
remove
theThe
dust,
treated,
and
combed
to
otherwise
be
sent
landfill
sites.
The
calcium
hydrated
lime
used
as the
binder
class
tionally
used
to
carry
and
store
potatoes,
cereals,
coffee,
etc.
broken
bags
were
make
the into
fiber
suitable
forand
the
preparation
The
opus
signinum
was
obtained
chopped
into
small
pieces
later
washed
to of
remove
the dust,
treated,
and
combed
to was
tionally
used
to to
carry
and
store
potatoes,
cereals,
coffee,
etc.
The
broken
bags
were
from
crushed
tiles,
no
longer
usable
for The
their
primary
covering
function,
and
which
would
otherwise
be
sent
to
landfill
sites.
calcium
hydrated
lime
used
as
the
binder
was
make
the
fiber
suitable
for
the
preparation
of
samples.
The
opus
signinum
was
obtained
chopped
into
small
pieces
and
later
washed
to
remove
the
dust,
treated,
and
combed
to
CL
80-S
according
topieces
EN
[35].
The
clayThe
was
collected
from
local
extraction
in class
make
the
fiber
suitable
for459-1:2015
theusable
preparation
ofto
samples.
opus
signinum
wascombed
obtained
from
crushed
tiles,
no
longer
for
their
primary
covering
function,
and which
would
chopped
into
small
and
later washed
remove
the
dust,
treated,
and
to
otherwise
be
sent
to
landfill
sites.
The
calcium
hydrated
lime
used
as
the
binder
was
class
CL
80-S
according
to
EN
459-1:2015
[35].
The
clay
was
collected
from
local
extraction
in
make
the
fiber
suitable
for
the
preparation
of
samples.
The
opus
signinum
was
obtained
from
crushed
tiles,
no
longer
usable
for
their
primary
covering
function,
and
which
would
from
crushed
tiles,
longer
usable
for
primary
covering
function,
and
which
would was class
central
bytono
removing
sediments
with
ahydrated
steel
mesh
sieve
and
water.
makeSardinia
thebe
fiber
suitable
for the
preparation
of
samples.
The
opus
signinum
otherwise
sent
landfill
sites.
Thetheir
calcium
lime
used
aswas
theobtained
binder
80-S
according
to
EN
459-1:2015
[35].
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clay
was
collected
from
local
extraction
in
from
crushed
tiles,
no
longer
usable
for
their
primary
covering
function,
and
which
would
central
Sardinia
by
removing
sediments
with
a
steel
mesh
sieve
and
water.
otherwise
be
sent
to
landfill
sites.
The
calcium
hydrated
lime
used
as
the
binder
was
class
Energies 2021, 14, x FORCL
PEER
REVIEW
4
of
16
otherwise
be sent
toto
landfill
sites. for
The
calcium
hydrated
lime used
aswhich
the
binder
was three
class
from
tiles,
no
longer
usable
their
primary
covering
function,
and
would
Thecrushed
twelve
samples
and
consequently
analyzed
can
be
classified
into
CL
80-S
according
EN realized
459-1:2015
[35].
The
clay
was
collected
from
local
extraction
in
otherwise
be
sent
sites.
The
calcium
hydrated
lime
used
as
binder
was
class
CL
80-S
according
tolandfill
EN
459-1:2015
[35].
The
clay
was
collected
from
local
extraction
in
central
Sardinia
byto
removing
sediments
with
aclay
steel
mesh
sieve
and
water.
The
samples
realized
and
consequently
analyzed
can
be
classified
into
otherwise
be twelve
sent
toto
landfill
sites.
The
calcium
hydrated
lime
used
as the
the
binder
was
class
CL
80-S
according
EN
459-1:2015
[35].
The
was
collected
from
local
extraction
inthree
different
groups
depending
on
whether
the
mixtures
are
intended
for
preparation
with
central
Sardinia
by
removing
sediments
with
a
steel
mesh
sieve
and
water.
CL
80-S
according
to
EN
459-1:2015
[35].
The
clay
was
collected
from
local
extraction
in
central
Sardinia
by to
removing
sediments
with
aclay
steel
mesh
sieve and
water.
CL
80-S
according
EN
459-1:2015
[35].
The
was
collected
from
local
extraction
in
The
twelve
samples
realized
and
consequently
analyzed
can
be
classified
into
three
different
groups
depending
on
whether
the
mixtures
are
intended
for
preparation
with
central
Sardinia
removing
with
a steel
mesh
sieve
and
water.
of
in
landfills
or
incinerators.
The sediments
jute fiber
wasplaster
collected
from
recycled
jute bags,
tradinatural
fibers
or by
recycled
materials:
(i)
with
natural
fibers;
(ii)
withinto
recycled
The
twelve
samples
realized
and
consequently
analyzed
can
beplaster
classified
three
central
Sardinia
by
removing
sediments
with
aa steel
mesh
sieve
and
The
twelve
samples
realized
and
consequently
analyzed
can
bewater.
classified
into
three
central
Sardinia
by
removing
sediments
with
steel
mesh
sieve
and
water.
tionally
used
to
carry
and
store
potatoes,
cereals,
coffee,
etc.
The
broken
bags
were
different
groups
depending
on
whether
the
mixtures
are
intended
for
preparation
with
natural
fibers
or recycled
materials:
(i) plastersuch
with
naturalcan
fibers;
(ii) plaster
with
recycled
The
twelve
samples
realized
and
consequently
analyzed
be
classified
three
materials;
and
(iii)
building-insulation
materials;
samples
are
presented
ininto
Table
2.
The
twelve
samples
and
consequently
analyzed
can
be
classified
into
three
different
groups
depending
mixtures
are
intended
preparation
with
different
groups
depending
onwhether
whether
the
mixtures
are
intended
for
preparation
with
chopped
into
small
pieces realized
and on
later
washed
to the
remove
the
dust,
treated,
and
to
The
twelve
samples
realized
and (i)
consequently
analyzed
cancombed
befor
classified
into
three
natural
fibers
or
recycled
materials:
plaster
with
natural
fibers;
(ii)
plaster
with
recycled
materials;
and
(iii)
building-insulation
materials;
such
samples
are
presented
in
Table
2.
different
groups
depending
on
whether
the
mixtures
are
intended
for
preparation
with
make
the fiber
suitable
for materials:
the preparation
of
samples.
The natural
opus are
signinum
was(ii)
obtained
different
groups
depending
on
the
intended
for
with
natural
fibers
orrecycled
recycled
(i) (i)
plaster
with
fibers;
plaster
with
recycled
different
groups
depending
on whether
whether
the mixtures
mixtures
are
intended
for preparation
preparation
with
natural
fibers
or
materials:
plaster
with
natural
fibers;
(ii)
plaster
with
recycled
from
crushed
tiles,
no longer
usable for their
primary
covering
function,
and
which
would
materials;
and
(iii)
building-insulation
materials;
such
samples
are
presented
in
Table
2.
natural
fibers
or
recycled
materials:
(i)
plaster
with
natural
fibers;
(ii)
plaster
with
recycled
materials;
and
(iii)
building-insulation
materials;
such
samples
are
presented
in Table
2.in Table
natural
fibers
or
recycled
plaster
with
natural
fibers;
(ii)presented
plaster
with
recycled
Table
2. building-insulation
Detailsmaterials:
of the analysed
samples.
natural
fibers
or
recycled
(i) (i)
plaster
with
fibers;
with
recycled
materials;
and
(iii)
materials;
such
samples
are
2.
otherwise
be
sent
to landfillmaterials:
sites. The calcium
hydrated
limenatural
used
as the
binder(ii)
wasplaster
class
Table
2. Details
of the materials;
analysed
samples.
materials;
and
(iii)
building-insulation
such
samples
are
presented
in
CL 80-S
according
to EN 459-1:2015 [35]. The
clay
was collected
from local
extraction
in presented
materials;
and
(iii)
materials;
samples
are
materials;
and
(iii) building-insulation
building-insulation
materials;
such such
samples
are
presented
in Table
Table 2.
2.in Table 2.
Energies 2021, 14, x FOR PEER REVIEW
tionally used
Energies
of in landfills
Energies 2021,
2021, 14,
14, x
x FOR
FOR PEER
PEER REVIEW
REVIEW
Water to
Table2.
2.
Details
ofof
the
analysed
the
analysed
samples.
centralTable
Sardinia
byDetails
removing
sediments
with asamples.
steel
mesh sieve and water.
SampleSample
Id. Number
and
Sample
Composition
Table
2.
Details
of
the
analysed
samples.
Water
to
Id.
Sample
The
twelve
samples
realized
and
consequently
analyzed
can
be
classified
into
three
Table
2.
Details
of
the
analysed
samples.
Group
Materials
Used
Binder
TableSamples
Details ofofthe
analysed
samples.
Water to Water to
Table
2.2.depending
Details
the
analysed
samples.
different
groups
on whether
the mixtures
are intended
for preparation
Dimensions
Dry
Weightwith
[%]
Binder
Ratio
Group
Number
and
Samples
Materials
Used
Composition
Sample
Id. Number
and
Sample
Composition
Density
and
Composition
Water
to Ratio [%]
natural
fibers orSamples
recycled materials:
(i) plaster with
natural fibers;Sample
(ii) plaster with
recycled
Group Sample Id. Number
Materials
Used
Binder
to
[%]
Dimensions
Dry
Weight
[%] 2.Water to Water
Sample
Id.
and
Sample
Composition
Density
]
Dry
Weight
[%]
[kg/m3to
Group
Samples
Materials
Used
Binder
Sample
Id.Dimensions
Number
and
Sample
Composition
materials;
building-insulation
materials;
such
samples
are
presented
in Table
Sample
Id. Number
Number
andand (iii)
Sample
Composition
Density
Samples
Materials
Binder
LimeUsed
putty
44%
S13
Ratio
[%] Water
Dimensions
Dry
Weight
[%]
Group Group
Samples
Materials
Used
Binder
3
Group Sample
Samples
Materials
Used
Binder
Dry
Weight
[%]
[kg/m
Id.Dimensions
Number and
Sample
Composition
3]
Ratio
[%]
]
Dimensions
Dry
Weight
[%]
[kg/m
Dimensions
Dry
Weight
[%]
Ratio
[%]
S13
Lime
putty
44%
Lime
putty
44% 45% Ratio [%]Ratio
S13
Group
Samples
Materials
Binder
Sand Used
Table
2. Details of the analysed
samples.
[%]
Dimensions
Dry
Weight
[%]
32%
Lime
putty
44%
S13S13
Lime
putty
44%
Sand
45%
32%
Sand
45%
Ratio
[%]
Lime
putty
44%
S13
Water44%
to
(300×
× S13
300
mm
))
Lime
putty
(300
300
mm22Number
1684.46
Sample
and
Sample Composition45%
Density 32%
Sand
Calcium
Calcium
carbonate
11%
(300
× 300Id.
mm2)
Sand
45%
Group
Samples
Materials
Used
Binder
Sand
45%
Lime
putty
44%
S13
1684.46
Dimensions
Dry Weight [%] 11%
[kg/m ] 32%
11%
Calcium
carbonate
32%
Sand
45%
32%
1684.46
2
Ratio [%]
×× 300
mm
carbonate
2) 2))
(300
300
mm
(300 (300
× 300
mm
32%
Calcium
carbonate
11%
Sand
45%
Lime
putty
44%
2)
Calcium
carbonate
11%
Lime
putty
&
Opus
Calcium
carbonate
11%
(300 × 300 mmS13
Lime
putty &
Opus& 45%
32%
S10
Sand
Lime
putty
Calcium
carbonate
11%
44%32%44%
(300 × S10
300S10
mm2)
signinum
44%11%1684.46
Lime
putty
&
Opus
signinum
(300 × 300 mm )
Lime
puttysigninum
&carbonate
Opus 11%
Calcium
Opus
S10
44%
Calcium
carbonate
32%
32%
1793.1
Lime
putty & Opus
S10
44% 45%
signinum
32%
Sand
45%
Sand
S10
44%
signinum
Lime
putty
Sand& Opus
45%44%
22) 2)
32%
1793.1
(300
× 300
mm
Plaster with
Lime putty &signinum
Opus
(300
×
300
mm
32%
1793.1
S10
Sand
45%
300 mmS10) 2
44%
Lime
putty
& Opus
Calcium
carbonate
11%
Plaster
with Recycled(300 ×
Sand
45% 11%
Calcium
carbonate
Plaster with
Recycled
signinum
signinum
32%
Calcium
(300
×× 300
Recycled
S10
44%1793.1
(300
300 mm
mm2))
32%45%
11%
Sand
Calcium
carbonate
11%
Plaster
with
Recycled
32%
Materials
Lime
putty
41.50%
S12 2
Sand
45%
signinum
Calcium
carbonate
11%
Plaster
with
Recycled
carbonate
Materials
Lime
putty
41.50%
× 300
mm )
(300 × S12
300 (300
mm
)
Sand
45%
Materials
32%
Calcium
carbonate
11%
Materials
Plaster with(300
Recycled
Lime
putty
41.50%
Opus
signinum
18.50%
Calcium
carbonate
× 300S12
mm2)
Plaster with Recycled
Materials
Lime
putty
41.50% 11%
S12
Sand
45%
33%
1793.1
Opus
signinum
18.50%
Lime
putty
S12
2) 2
Calcium
carbonate
11%
S12
Lime
putty 41.50% 18.50%
41.50%
Plaster with Recycled Materials
(300
×
300
mm
Opus
signinum
(300
×
300
mm
)
33%
Opus
signinum
Materials
Lime
putty 18.50% 18.50%
41.50%
S12
Opus
signinum
1793.1
Calcium
carbonate
11%1793.1 33%
Sand
40%
PlasterMaterials
with Recycled
2) 2
33%
1793.1
Opus
signinum
18.50%
33%
(300 (300
× S12
300
mm
33%
Lime
putty
41.50%
×× 300
)) )
2 ) 2mm
(300
×mm
300
(300
300
mm
(300
×
300
mm
Sand
40%
Sand
40%
Opus
signinum
18.50%
Sand
40%
Materials
Lime
putty
41.50%
S12S09
Sand
40%
Sand
40%
33%
Opus
signinum
44%
Opus
signinum
18.50%
2)
(300 × 300S09
mmS09
33%
Opus
signinum
44%
Opus
signinum
18.50%
Opus
signinum
44%
2
Sand
45%
Opus
signinum
44%
44%
Opus
signinum
44%
Sand
40%
(300 × S09
300S09
mm )
33%
Sand
45%
32%
1659.58
2) 2)
32%40%1659.58
Sand
Sand
45%
× 300
(300 (300
× 300
mm
Sand
45%
Sand
45%
(300
×mm
300
32%
Sand
45%
32%
1659.58
2 ) 2mm )
Calcium
carbonate
11%
Calcium
carbonate
11%
Sand
40%
32%
1659.58
(300 ×
300
mm
32%
(300
×× 300
mm
)
Opus
signinum
44%
S09
Calcium
300
mm
2) 2)
Calcium
carbonate
11%
(300 (300
× S09
300
mm
Opus
signinum
11%44%
Calcium
carbonate
11%
Sheep
wool fibre
3%
Sheep
wool
fibre
3% 11%
Calcium
carbonate
S14
carbonate
Sand
45%
Opus
44%
S09S14
Lime
putty signinum16%
32%
Sand
45%
Sheep
wool
fibre
3%
Lime
putty
16%
Sheep
wool
fibre 36%
3% 39%
Opus
signinum
1390.91
(300 × 300S14
mm22)
32%
Sheep
wool
Sand
45%
S14
Sheep
wool
fibre
3%
Lime
putty
16%
Calcium
carbonate
11%
(300 × 300 (300
mm
) mm )
Opus
signinum
36%
39%
1390.91
Sand
35%
× 300
3%
32%
Lime putty
16%
S14
2)
Calcium
carbonate
11%
fibre
(300 (300
× S14
300
mm
Calcium
carbonate
2)
Opus
signinum
36%
39%
1390.91
Lime
putty 9%
Sand
35%
× 300
mm
Opus
signinum
36% 16%
39%
1390.91
Calcium
carbonate
11%
Lime
putty
16%
SheepSheep
wool fibrewool fibre
4%
3%
Sand
35%
(300
×× 300
S11 22))
Calcium
carbonate
9%
39%
Opus
signinum
36%
39%
Sand
35%
(300
300 mm
mm
S14
Sheep
wool
fibre
3%
Lime
putty
43%
Opus
signinum
36%
39%16%1114.61
Lime
putty
S14
Calcium
carbonate
9%
Sheep
fibrefibre
4%
Sheep
wool
3%
Sand wool
42%
22)
Calcium
carbonate
9%
Sand
35%
(300
×
300
mm
Lime
putty
(300
× 300
Sand
35%16%
(300 × S14
300S11
mm
) mm )
Calcium
carbonate
Sheep
wool
fibre
4%
Opus
signinum
39%
Lime
putty
43%
Sheep
wool
fibre 11%
4% 36%
Lime
putty
16%
S11
Calcium
carbonate
9%
39%
1114.61
Plaster with Natural
Opus
signinum
36%
39%
SheepCalcium
Wool
&
ThisS11 2
Lime
putty
43%
9%
3%
Sand
42%
)
Sand
(300 × 300
mm
Lime
putty
43% 35%
Fibres
tleOpus
fibres
signinum
36%
39%
39%
1114.61
carbonate
× 300
mm
2) 2)
Sheep
wool
fibre
4%
39%
1114.61
S06
Sand
35%
(300 (300
× 300
mm
Sand
42%
Calcium
carbonate
11%
Lime
putty
16%
Sand
42%39% 9%1101.48
S11
Calcium
carbonate
2) 22)
×
300
mm
Sand
35%
(300 (300
×
300
mm
(300 × 300 mm )
Lime
putty
43%
Opus
signinum
Sheep
wool
Calcium
carbonate
11%
Calcium
carbonate
9%
Plaster with Natural
Sheep
Wool
&
This- 36%
Calcium
carbonate
11%
39%
3% 4% 4%
Sheep
wool
fibre
SandWool
35%
Calcium
carbonate
9%
Plaster
with
Natural
fibre
Fibres
Sheep
&
ThisS11
tle
fibres
(100 × 100 mm )
Sand
42%
S11S06
Plaster with Natural
Sheep
wool
fibre
4%
Sheep
Wool
&
This3%
Calcium carbonate
9%
2)
(300
×
300
mm
3%
Lime
putty
43%
S11
Fibres
tle
fibres
Lime
putty
39%
Sheep
wool
fibre
4%
Lime
putty
16%43%11%
Fibres
tle
SheepCalcium
Wool
&fibres
Thiscarbonate
39%
Lime
putty
43%
39%
1101.48
S11S06
4%
S06 S05
putty
16%
42%42%
Sand
tle Lime
fibres
39%
Opus
signinum
36%
Lime
putty
43%
2
Lime
putty
16%
Plaster with Natural
39%
1101.48
(300
Sheep
Wool
&
This(300×
× 300 mm22))
Sand
42%
Lime
putty
43%
1101.48
36%
39%
Calcium
Opus
signinum
36%
3%1206.06 39%
Sand
35%
Calcium
carbonate
11%
(300 (100
× 300
mm
) 2)
Opus
signinum
36%
42%
11%11%
Plaster with
Sand tleSand
42%
Fibres
× 100
mm
fibres
2) mm
Calcium
carbonate
(100
× 100
)
carbonate
Sand
35%
(300
×
300
mm
Calcium
carbonate
9%
Sand
35% 11%
S06
2
Calcium
Carbonate
11%
PlasterNatural
with Natural
Sheep
Wool
& This(100
Fibres
Calcium
carbonate
(100 ×× 100
100 mm
mm2))
Lime
putty
16%
3%
Plaster with Natural
Calcium
carbonate
9%
Sheep
Wool
& ThisSheep
Wool
&
ThisCalcium
carbonate
9%
Sheep
Wool
&
Fibres
39%
tle
fibres
3%
4%
Plaster Fibres
with Natural
Sheep
Wool
&
This3%
Sheep
Wool
&
ThisOpus
signinum
36%
tle
fibres
tle
fibres
S06S05
SheepThistle
Wool &fibres
This3%
4%
Lime
putty
S06S05
4% 16%
Fibres
tle
fibres
S06
tle
fibres
Lime
putty
43%
36%
1206.06
Sand
tle
fibres
S05
Lime
putty
16%
39%
16%35%
(100 × S06
100 mm2)
Opus
signinum
36%
Lime
putty
43%
39%
39%
36%
1206.06
Sand
42%
Lime
putty
16%
Lime
putty
43%
36%
1206.06
Opus
signinum
36%
2
Calcium
carbonate
9%
36%
(100 × 100 mm )
39%
Sand
42%
Calcium
Carbonate
11%
Sand
35%
Sand
42%
Opus
signinum
36%
Sand
35%35%
22) 22)
(100
×× 100
mm
Sheep
Wool
&
This(100
×
100
mm
Sand
(100
100
mm
)
(100
100 mm
mm2))
Calcium
Carbonate
11%
4%
Calcium
Carbonate
11% 35%
Calcium
carbonate
9%
(100×
× 100
Calcium
Sand
tle
fibres
9% 9%
Calcium
carbonate
(100 × S05
100 mm2)
carbonate
Sheep
Wool
& ThisCalcium
carbonate
9%
Lime
putty
43%
36%
4%
Sheep
Wool
& Thistle
fibres
S05
4%
Sheep
Wool
&
Sheep
Wool
&
ThisSand
42%
tle
fibres
S05
4% 4%
(100 × S05
100 mm2)
Lime
putty
43%
Thistle
fibres
36%
tle fibres
S05
Calcium
Carbonate
11%
Lime
putty
43%
36%
Lime
putty
43%
36%
Sand
42%
Lime
putty
43%
36%
(100 × 100 mm22)
Sand
Sand
42%42%
Calcium
Carbonate
11%
(100×
× 100
Sand
42%
(100
100 mm
mm22))
Calcium
Carbonate
11%
Calcium
(100 × 100 mm )
11%11%
Calcium
Carbonate
Carbonate
3
2
2
2
2
2
2
2
Density
Density
3]
[kg/m
[kg/m3 ]
Density
Density
[kg/m3]
Density
[kg/m3]
3]
[kg/m
1684.46
1684.46
1684.46
1684.46
1684.46
1793.1
1793.1
1793.1
1793.1
1793.1
1793.1
1793.1
1793.1
1793.1
1793.1
1659.58
1659.58
1659.58
1659.58
1659.58
1390.91
1390.91
1390.91
1390.91
1390.91
1114.61
1114.61
1114.61
1114.61
1114.61
2
1101.48
1101.48
1101.48
1101.48
1101.48
1206.06
1206.06
1206.06
1206.06
1206.06
Energies 2021, 14, 3564
5 of 16
Table 2. Cont.
Energies 2021, 14, x FOR PEER REVIEW
5 of 16
Sample Id.
Energies 2021, 14, x FOR PEER REVIEW
Energies
REVIEW
Group2021, 14, x FOR PEER
Number
and
Energies 2021, 14, x FOR PEER REVIEW
Dimensions
S08
S08 S08
S08
S08 2
(300 ×(300
300×mm
) 2)
300 mm
2 ) 2)
300 mm
(300 ×(300
300× mm
(300 × 300 mm2)
S07
S07 S07
S07
S07
(300 × 300 mm2)
Building
Insulation
2) 2)
300 mm
Building
(300 ×(300
300×mm
2)
Buildingwith
Insulation
(300 × 300 mm
Materials
Natural
BuildingInsulation
Insulation
(300 × 300 C02
mm2 )
Buildingwith
Insulation
Materials
Natural
Fibres
Materials
with
Natural
C02
Materials
with
Materials
with Natural
Fibres
C02 C02
Fibres Fibres
Fibres
Natural
(100 × 100 mm2)
(100 × 100 mm2)
2
100 mm
2) )
(100 ×(100
100×mm
2
(100 × 100 C01
mm )
C01
(100 × 100 mm2)
(100 × C01
100 mm2)
2
(100
C01× 100 mm )
2
2
(100 × 100 mm )
Samples
Materials Used
Hemp shives
Hemp
shives
Hemp
shives
Lime
putty
Hemp
shives
Lime putty
Hemp
shives
Lime putty
Lime
putty
Lime
putty
Opus
signinum
Opus
signinum
Opus
signinum
Opus
signinum
Opus
signinum
Hemp
shives
Hemp
shives
Hemp
shives
Hemp
shives
Hemp shives
Lime putty
Lime
puttyputty
Lime
Lime putty
Lime
putty
Hemp
shives
Hemp shives
Hemp
shives
Hemp shives
Clay
Clay
Clay
Clay
Clay
Jute fibre
Jute
fibre
Clay
Jute
fibre
Clay
Clay
Jute fibre
Sample
Composition
Dry Weight [%]
50.50%
50.50%
50.50%
50.50% 42.20%
42.20%
50.50%
42.20%
42.20%
42.20%
7.30%
7.30%
7.30%7.30%
7.30%
55%
55%
55% 55%
55%
45%
45%
45%
45%
30% 45%
30%
30% 30%30%
70%
70%
70%
21%
21%
79%
21%
79%
79%
Water
to
5 of 16
5 of 16
Binder
Ratio
5 of 16
[%]
39%
39%
39%
39%
489.94
39%
489.94
489.94
39%
39%
39%
459.06
39%
459.06
39%
459.06
39%
39%
39%
436.6
436.6
436.6
39%
39%
39%
39%
39%
807.41
807.41
807.41
70%
70%
21%21%
39%
39%
(100 × 100In
mm
Clay
79%
) 2, the discarded samples are also
Table
shown. Samples S0179%
and
S04 were sheep wool
Density
[kg/m3 ]
489.94
489.94
459.06
459.06
436.6436.6
807.41
807.41
In
Table
2, the
discarded
samples
are
also
shown.
Samplescarbonate
S01 and S04
were sheepmorewool
mixed
with
lime
putty as the
binder
and
sand
and calcium
as aggregates;
In Table
2, the
discarded
samples
are
also
shown.
Samplescarbonate
S01 and S04
were sheepmorewool
mixed
with
lime
putty
assigninum
the
binder
sand
and
as shives
aggregates;
over, S01
also
used
opus
asand
a binder.
S02calcium
and S03 used hemp
mixed with
mixedS01
with
lime
putty
assigninum
the binderasand
sand and
calcium
carbonate
as shives
aggregates;
moreover,
also
used
opus
a
binder.
S02
and
S03
used
hemp
mixed
lime putty (also opus signinum in S02) as the binder, but no aggregates were usedwith
for
over, S01
also
used
opus
signinum
a binder.
and S03
used
hemp
shives
mixed
In Table
2, the
discarded
samples
are
shown.
Samples
S01
and
S04
were
sheep wool
lime
(also
opus
signinum
inas
S02)
asalso
theS02
binder,
but
no
aggregates
were
usedwith
for
theseputty
last
two.
The
water
was
added
accordingly
and
based
on
the guidance
provided
by
In
Table
2,
the
discarded
samples
are
also
shown.
Samples
S01
and S04 were sheep
lime putty
(also
opus
signinum
in S02)
as the binder,
but no
aggregates
were
used for
these
last
two.
The
water
was
added
accordingly
and
based
on
the
guidance
provided
by
mixed
with
limefrom
putty
theexperience.
binder and sand and calcium carbonate as aggregates; morea local
artisan
his as
work
these
last
two. from
The
water
wasexperience.
added as
accordingly
and based
on theand
guidance
provided
by
wool
mixed
with
putty
the binder
and sand
calcium
carbonate
as aggregates;
artisan
his lime
work
over,aa local
S01
also
used
opus
signinum
as a binder. S02 and S03 used hemp shives mixed with
local
artisan
from
his
work
experience.
moreover,
S01 also
opus signinum as a binder. S02 and S03 used hemp shives mixed
2.2.
Sample Preparation
andused
Conditioning
lime2.2.
putty
(also
opus and
signinum
in S02) as the binder, but no aggregates were used for
Sample
Preparation
Conditioning
with
lime
putty
(also
opus
signinum
in S02)
as theusing
binder,
but
no aggregates
were used for
The
first
four
samples
(from
S01 to S04) were
prepared
wood
casting
molds
Sample
Preparation
and Conditioning
these2.2.
last
two.
The
water
was
added
and based
on the
guidance
provided by
Thelast
firsttwo.
four S01
samples
(from
S01
to accordingly
S04) were
prepared
usingbased
wood
casting
molds
(i.e.,
samples
from
to water
S04).
After
preparing
the
grout,
the samples
were kept
to mature
these
The
was
added
accordingly
and
on
the
guidance
provided
by a
The firstfrom
four S01
samples
(from
S01
to S04) were
prepared
using wood
casting
molds
a local
artisan
histowork
experience.
(i.e.,
samples
from
S04).
After
preparing
the grout,
thethe
samples
were kept
mature
and
dry
naturally.
Following
the
total
maturation
period,
first samples
(seetoS02
and
local
artisan
from
his
work
experience.
(i.e.,
samples
from
S01
to
S04).
After
preparing
the
grout,
the
samples
were
kept
to
mature
and
dryTable
naturally.
Following
the total
maturation
the first because
samplesof
(see
and
S03 in
3) showed
brittleness
when
touched; period,
this happened
theS02
higher
and in
dryTable
naturally.
Following
the total
maturation
period,
the first because
samplesof
(see
S02
and
S03
3) showed
brittleness
when
touched;
this happened
theto
higher
fiber
concentration
than
the
mixture’s
binder.
In
contrast,
a
high
binder
content
fibers
2.2. Sample
Preparation
and
Conditioning
S03
Table
3) Preparation
showed
brittleness
when
touched;
this happened
because
of thetohigher
2.2.inconcentration
Sample
and Conditioning
fiber
than
the
mixture’s
binder.
In
contrast,
a
high
binder
content
fibers
(S01 and S04 in Table 3) led to big cracks on the surfaces with time. These problems are
fiber
concentration
than
the
binder.
In contrast,
a prepared
high
binder
content
to fibers
Theand
first
four
samples
S01
tothe
S04)
were
using
wood
(S01
S04with
in Table
3)samples
led mixture’s
to(from
big
cracks
on
surfaces
with
time.
These
problems
arecasting
The
first
four
(from
S01
to
S04)
were
using
wood
castingmolds
molds (i.e.,
easily
dealt
the
deposition
of further
filling
mortar,
but
it isprepared
clear that
these
situations
(S01 and
S04
in Table
3) led to big
cracksfilling
on themortar,
surfaces
with
time.
These
problems
are
easily
dealt
with
the
deposition
of
further
but
it
is
clear
that
these
situations
(i.e.,are
samples
from
S01
to
S04).
After
preparing
the
grout,
the
samples
were
kept
to
mature
not
acceptable
for
thermal
conductivity
tests.
samples
fromtheS01
to S04).ofAfter
the grout, the samples were kept to mature and
easily
with
furtherpreparing
filling
notdealt
acceptable
fordeposition
thermal conductivity
tests.mortar, but it is clear that these situations
and are
dry
naturally.
Following
the
maturation
dry
naturally.
Following
thetotal
totaltests.
maturationperiod,
period,the
thefirst
firstsamples
samples(see
(seeS02
S02and
and S03
are
not
acceptable for
thermal conductivity
S03 ininTable
happened because
because of
of the
the higher
higher fiber
Table 3)
3) showed
showed brittleness
brittleness when
when touched;
touched; this
this happened
fiber concentration
concentration than
the
mixture’s
binder.
In
contrast,
a
high
binder
content
to
than the mixture’s binder. In contrast, a high binder content to fibers
fibers (S01
(S01 and
Table 3)
3) led
led to
to big
bigcracks
crackson
onthe
thesurfaces
surfaceswith
withtime.
time.These
Theseproblems
problemsare
areeasily
and S04
S04 in
in Table
easilydealt
dealtwith
withthe
thedeposition
depositionofoffurther
furtherfilling
filling
mortar,
but
it is
clear
that
these
situations
mortar,
but
it is
clear
that
these
situations
are not
are not
acceptable
thermal
conductivity
tests.
acceptable
forfor
thermal
conductivity
tests.
Indeed, as highlighted in [26–29], the fiber size and percentage in the mixture (binder
and fiber) directly influence the strength and the thermal conductivity of any building
material, therefore, particular attention was paid while preparing the succeeding samples.
Taking into account the experience gained during the preparation of the first samples
(S01 from S04), the authors tried to improve the homogeneity of the mixture by slow
manual mixing to avoid air trapping and poured the mixture into 100 × 100 mm2 and
300 × 300 mm2 wooden molds, with various thicknesses from 5 to 100 mm.
The grout was prepared following UNI EN 1015-2 [36] and the consistency of the
mixture was verified using the shaking table tests UNI EN 1015-3 [37].
After the grout’s workability condition was proven, the wooden molds were first half
filled with the mixture and 25 strokes were applied with a stick with the aim to distribute
the mixture uniformly and to also remove any air bubbles from inside according to [37].
The molds were completely filled, and another 25 strokes were applied and then the upper
surface was levelled. Thereafter, the sample was left inside the mold and placed inside
a plastic bag for two days. After two days, the samples were taken out of the mold and
re-placed inside another plastic bag for five days, which was done to provide a quasi-stable
Energies 2021, 14, 3564
6 of 16
condition during the sample’s maturation. After seven days from the date of casting, the
samples were put outside to dry naturally, in a dedicated room with controlled temperature
◦ C, 60%). The progressive weight reduction of each sample was measured
and
humidity
(20PEER
Energies
2021, 14, x FOR
REVIEW
Energies 2021, 14, x FOR PEER REVIEW
regularly
period
of 28 days.
Energies 2021, for
14, x a
FOR
PEER REVIEW
Energies 2021, 14, x FOR PEER REVIEW
6
6
6
6
of
of
of
of
16
16
16
16
Table 3. Discarded
samples,
prepared at the first attempt.
Table 3. Discarded samples, prepared
at the first
attempt.
Table 3. Discarded samples, prepared at the first attempt.
Table 3. Discarded samples, prepared at the first attempt.
Table 3. Discarded samples, prepared at the first attempt.
Sample
andand
Dimensions
SampleId.
Id.Number
Number
Dimensions
Sample Id. Number and Dimensions
Sample Id. Number and Dimensions
Sample Id. Number
and Dimensions
S04S04
S04
S04
S04
(100 × 100 mm22)
(100 × 100 mm2) 2
(100× 100
× 100
)
(100
mmmm
)
(100 × 100 mm2)
S03
S03S03
S03
S03
(100 × 100 mm22)
(100 × 100 mm2)
(100 × 100 mm2) 2
(100× 100
× 100
)
(100
mmmm
)
S02
S02
S02S02
S02
(100 × 100 mm22)
(100 × 100 mm2)
(100 × 100 mm2)
(100 × 100 mm ) 2
(100 S01
× 100 mm )
S01
S01
S01S01
(100 × 100 mm22)
(100 × 100 mm2)
(100 × 100 mm2)
(100 × 100 mm )
Samples
Samples
Samples
Samples
Samples
Materials
Materials
Used Used
Materials Used
Materials Used
Materials Used
Sheep wool
and
Lime
Sheep
wool
andputty
Lime putty
Sheep wool and Lime putty
Sheep wool and Lime putty
Sheep wool and Lime putty
Hemp shives and Lime putty
Hemp shives and Lime putty
Hemp shives and Lime putty
Hemp shives
Lime
Hempand
shives
andputty
Lime putty
Hemp shives, lime putty and opus
Hemp shives, lime putty and opus
HempHemp
shives,
lime
putty
andand opus
signinum
shives,
lime
putty
signinum
Hemp shives,
lime putty and opus
opus signinum
signinum
signinum
Sheep wool, lime putty and opus
Sheep wool, lime putty and opus
Sheep wool,signinum
lime putty and opus
SheepSheep
wool,wool,
limesigninum
putty
andand opus
lime
putty
signinum
opus signinum
signinum
(100 × 100 mm2 ) Indeed, as highlighted in [26–29], the fiber size and percentage in the mixture (binder
s 2021, 14, x FOR PEER REVIEW
Progressive reduction of sample
weight (%)
30%
25%
20%
15%
10%
5%
0%
Indeed, as highlighted in [26–29], the fiber size and percentage in the mixture (binder
and fiber)
directly
influenceinthe
strength
and size
the thermal
conductivity
any building
Indeed,
as highlighted
[26–29],
the fiber
and percentage
in the of
mixture
(binder
and fiber)
directly
influenceinthe
strength
and size
the thermal
conductivity
any building
Indeed,
as highlighted
[26–29],
the fiber
and percentage
in the of
mixture
(binder
material,
particular the
attention
wasand
paidthe
while
preparing
the succeeding
and
fiber)therefore,
directly influence
strength
thermal
conductivity
of any samples.
building
therefore,
particular
attention
wasand
paid
while
preparing
the
succeeding
To show an examplematerial,
of
the
drying
Figure
1
shows
the
trend
of
the
progressive
and
fiber)
directlyphase,
influence
the
strength
the
thermal
conductivity
of any samples.
building
Taking into
accountparticular
the experience
gained
the preparation
of the
first samples
(S01
material,
therefore,
attention
wasduring
paid while
preparing the
succeeding
samples.
Taking
into
account
the
experience
gained
during
the preparation
of the
first
samples
(S01
material,
therefore,
particular
attention
was
paidrepresentative
while
preparing the
succeeding
samples.
weight reduction of four
samples
(C01,
S08,
S10,
S11),
each
given
from
S04),
authors
tried
to improve
the
homogeneity
of the mixture
by
slow
manual
Taking
intothe
account
the
experience
gained
during
the preparation
ofof
theafirst
samples
(S01
from
S04),
the
authors
tried
to
improve
the
homogeneity
of
the
mixture
by
slow
manual
Taking into account the experience gained during the preparation of the first
samples (S01
2
sample category. Duringfrom
the sample’s
maturation
(i.e.,
from
the
thirdinto
toofthe
day),
a300
mixing
to avoid
air
trapping
poured
mixture
100
×mixture
100 mm
and
× 300
S04),
the authors
tried toand
improve
thethe
homogeneity
theeighth
by
slow
manual
2 and 300 × 300
mixing
to avoid
air trapping
poured
mixture intoof100
100 mmby
from2 S04),
the authors
tried toand
improve
thethe
homogeneity
the×mixture
slow manual
mmof
wooden
molds,
with0.6%
various
thicknesses
from 5 tointo
100100
mm.
mixing
to avoid
airthan
trapping
and
poured
the
mixture
× 100observed
mm22 and 300 × 300
controlled daily reduction
not
more
in
all
the
samples’
mass
was
2
mm
wooden
molds,
with various
thicknesses
from 5 tointo
100100
mm.× 100 mm and 300 × 300
mixing
to avoid
air trapping
and poured
the mixture
2 The
groutmolds,
was prepared
following
UNI EN
1015-2
[36]mm.
and the consistency of the
mmperiod,
wooden
with
various
from
5 day,
to 100
(Figure 1). In the following
from
eighth
tothicknesses
the fourteenth
during
which
the of the
grout
wasthe
prepared
following
UNI EN
1015-2
[36]
and the
consistency
mm2 The
wooden
molds,
with
various
thicknesses
from
5 to 100
mm.
mixture
was
verified
using
the
shaking
table
tests
UNI
EN
1015-3
The grout was prepared following UNI EN 1015-2
[36]16and[37].
the consistency of the
7
of
mixture
was
verified
using
thefollowing
shaking
table
tests
EN[36]
1015-3
[37].
The
grout
was
prepared
UNIunder
EN UNI
1015-2
and
the consistency
of the
samples were naturally dried,
a
rapid
daily
reduction
of
just
3%
was
observed.
For
After
theverified
grout’s using
workability
condition
proven,
the1015-3
wooden
molds were first half
mixture
was
the shaking
tablewas
tests
UNI EN
[37].
After
the
grout’s using
workability
condition
was
proven,
the1015-3
wooden
molds were first half
mixture
was
the
shaking
tableless
tests
UNI 0.2%
EN
[37].
the remaining days, the decrease
inverified
weight
was
on
average
than
daily.
filledAfter
with the
the
mixture
and
25
strokes
were
applied
with
a
stick
with
the
aim
to
distribute
grout’s workability condition was proven, the wooden molds were first half
filledAfter
with the
thegrout’s
mixtureworkability
and 25 strokes
were applied
with the
a stick
with molds
the aimwere
to distribute
condition
was proven,
wooden
first half
the mixture
uniformly
to strokes
also remove
air bubbles
fromwith
inside
to [37].
filled
with the
mixture and 25
were any
applied
with a stick
theaccording
aim to distribute
the
mixture
uniformly
to strokes
also remove
air bubbles
fromwith
inside
to [37].
filled with the mixture and 25
were any
applied
with a stick
theaccording
aim to distribute
Themixture
molds were
completely
filled,
another
were
applied
then thetoupper
the
uniformly
and to
alsoand
remove
any25
airstrokes
bubbles
from
insideand
according
[37].
The
molds were
completely
filled,
another
were
applied
then thetoupper
the mixture
uniformly
and to
alsoand
remove
any25
airstrokes
bubbles
from
insideand
according
[37].
surface
waswere
levelled.
Thereafter,
the
was
left inside
theapplied
mold and
inside
The
molds
completely
filled,
andsample
another
25 strokes
were
andplaced
then the
uppera
(S10)Lime
putty
and
Opus
surface
waswere
levelled.
Thereafter,
was
left inside
theapplied
mold and
inside
a
The molds
completely
filled,the
andsample
another
25 strokes
were
andplaced
then the
upper
plastic bag
two days.
After two
thewas
samples
were taken
out and
of the
moldinside
and re-a
surface
wasfor
levelled.
Thereafter,
thedays,
sample
left inside
the mold
placed
plastic
twosigninum
days.
After two
the was
samples
were taken
out and
of the
moldinside
and re-a
surfacebag
wasfor
levelled.
Thereafter,
thedays,
sample
left inside
the mold
placed
placed
inside
another
plastic
bag
for
five
days,
which
was
done
to
provide
a
quasi-stable
plastic bag for two days. After two days, the samples were taken out of the mold and replaced
inside
plastic
bag
fordays,
five
days,
which
was done
provide
quasi-stable
plastic bag
foranother
two(S11)
days.
After
two
theand
samples
were
takentoout
of theamold
and reSheep
wool
fiber
Lime
condition
during
the sample’s
maturation.
After
sevenwas
days
from
date of
casting, the
placed
inside
another
plastic bag
for five days,
which
done
tothe
provide
a quasi-stable
condition
during
the
sample’s
maturation.
After
sevenwas
days
from
date of
casting, the
placed inside
another
plastic bag
for five days,
which
done
tothe
provide
a quasi-stable
putty
samples
were
put
outside
to
dry
naturally,
in
a
dedicated
room
with
controlled
temperacondition during the sample’s maturation. After seven days from the date of casting, the
samples
putthe
outside
to dry
naturally, After
in a dedicated
room
with
temperaconditionwere
during
sample’s
maturation.
seven days
from
thecontrolled
date of casting,
the
ture andwere
humidity
(20 °C,
The progressive
weight room
reduction
each sample
was
Hemp
Lime
samples
put (S08)
outside
to60%).
dryshives,
naturally,
in aputty,
dedicated
with of
controlled
temperature
andwere
humidity
(20 °C,to60%).
The progressive
weight room
reduction
each sample
was
samples
put outside
dry naturally,
in a dedicated
with of
controlled
temperameasured
regularly
forOpus
a period
ofThe
28 days.
ture
and humidity
(20
°C,
60%).
progressive weight reduction of each sample was
and
signinum
measured
regularly
for °C,
a period
ofThe
28 days.
ture and humidity
(20
60%).
progressive weight reduction of each sample was
To show
an example
of the drying
phase, Figure 1 shows the trend of the progressive
measured
regularly
for a period
of 28 days.
(C01)
Jute
fiber
and
Clay Figure 1 shows the trend of the progressive
To
show
an
example
of
the
drying
phase,
measured regularly for a period of 28 days.
weight
of four samples
(C01, phase,
S08, S10,
S11),1each
representative
of aprogressive
given samTo reduction
show an example
of the drying
Figure
shows
the trend of the
weight
of four samples
(C01, phase,
S08, S10,
S11),1each
representative
of aprogressive
given samToreduction
show an example
of the drying
Figure
shows
the trend of the
ple category.
During
thesamples
sample’s(C01,
maturation
third to theofeighth
day),
a
weight
reduction
of four
S08, S10,(i.e.,
S11),from
eachthe
representative
a given
sample
category.
During
thesamples
sample’s(C01,
maturation
third to theofeighth
day),
a
weight
reduction
of four
S08, S10,(i.e.,
S11),from
eachthe
representative
a given
samcontrolled
daily
reduction
of not more
than 0.6%
in from
all thethe
samples’
was observed
ple
category.
During
the sample’s
maturation
(i.e.,
third tomass
the eighth
day), a
controlled
daily
reduction
of not more
than 0.6%
in from
all thethe
samples’
was observed
ple category.
During
the sample’s
maturation
(i.e.,
third tomass
the eighth
day), a
(Figure
1).
In
the
following
period,
from
the
eighth
to
the
fourteenth
day,
during
which
controlled daily reduction of not more than 0.6% in all the samples’ mass was observed
(Figure
1). daily
In thereduction
followingofperiod,
from
the 0.6%
eighth
day, was
during
which
controlled
not more
than
in to
allthe
thefourteenth
samples’ mass
observed
the samples
naturally dried,
daily
reduction
just underday,
3% was
observed.
(Figure
1). Inwere
the following
period,a rapid
from the
eighth
to theoffourteenth
during
which
the
samples
naturally dried,
daily
reduction
just underday,
3% was
observed.
(Figure
1). Inwere
the following
period,a rapid
from the
eighth
to theoffourteenth
during
which
For
the
remaining
days,
the
decrease
in
weight
was
on
average
less
than
0.2%
daily.
the samples were naturally dried, a rapid daily reduction of just under 3% was observed.
For
the remaining
days, the dried,
decrease
in weight
on average
than3%
0.2%
the samples
were naturally
a rapid
daily was
reduction
of justless
under
wasdaily.
observed.
For the remaining days, the decrease in weight was on average less than 0.2% daily.
For the remaining days, the decrease in weight was on average less than 0.2% daily.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Days
Figure 1. Example of the progressive weight reduction trend of four samples for the different typologies of materials taken
Figure 1. Example of the progressive weight reduction trend of four samples for the different typolinto account (C01, S08, S10, S11) during the drying phase (28 days).
ogies of materials taken into account (C01, S08, S10, S11) during the drying phase (28 days).
The residual moisture from the samples was removed before conducting the thermal
The residual
moisture from
was removed
conducting
the thermal
conductivity
tests,the
by samples
drying them
in oven atbefore
constant
temperature
(i.e., at about 40 ◦ C),
conductivity tests,
by
drying
them
in
oven
at
constant
temperature
(i.e.,
at
about
40
according to UNI EN-12667 [38]. During this period, the sample mass was°C),
measured hourly.
according to UNI EN-12667 [38]. During this period, the sample mass was measured
hourly. The final stability conditions were considered reached when the last 5 readings
remained within ±0.1 g.
For all the samples, the thermal conductivity tests were conducted only at the end of
the drying process. For three samples, additional thermal conductivity measurements
were carried out at regular intervals during the total drying period, to observe the varia-
Figure 1. Example of the progressive weight reduction trend of four samples for the different typologies of materials taken into account (C01, S08, S10, S11) during the drying phase (28 days).
Energies 2021, 14, 3564
The residual moisture from the samples was removed before conducting the thermal
7 of 16
conductivity tests, by drying them in oven at constant temperature (i.e., at about 40 °C),
according to UNI EN-12667 [38]. During this period, the sample mass was measured
hourly. The final stability conditions were considered reached when the last 5 readings
remained within ±0.1 g.
The final stability conditions were considered reached when the last 5 readings remained
For all the samples, the thermal conductivity tests were conducted only at the end of
within ±0.1 g.
the drying
For three
additional thermal
conductivity
Forprocess.
all the samples,
thesamples,
thermal conductivity
tests were
conductedmeasurements
only at the end of
werethe
carried
out
at
regular
intervals
during
the
total
drying
period,
to observe
the variadrying process. For three samples, additional thermal conductivity
measurements
were
tioncarried
in thermal
conductivity
value
with
respect
to
the
moisture
content.
out at regular intervals during the total drying period, to observe the variation in
In orderconductivity
to minimizevalue
the error
bythe
themoisture
sample surface
thermal
withinduced
respect to
content.roughness, (Figure 2)
when it was
not
possible
to
intervene
mechanically
by
abrasion,
the useroughness,
of a thermal(Figure
con- 2)
In order to minimize the error induced by the sample surface
ductive
film
of
grease
(Thermigrease
TG-20014)
was
applied.
when it was not possible to intervene mechanically by abrasion, the use of a thermal
conductive film of grease (Thermigrease TG-20014) was applied.
2 ), with sheep wool, thistle fibres and lime putty. The sample is
Figure
2. Sample
S05 (100
1002),
mm
Figure
2. Sample
S05 (100
× 100×mm
with
sheep wool, thistle fibres and lime putty. The sample is
showed
without
(a) and
(b) thermally
conductive
grease.
showed
without
(a) and
withwith
(b) thermally
conductive
grease.
Thermal
Conductance
Measurement
2.3. 2.3.
Thermal
Conductance
Measurement
The thermal conductivity tests were conducted by using a thermal conductivity
The thermal conductivity tests were conducted by using a thermal conductivity
measuring device TURUS TCA 300 (ISO 8301 [39] and DIN EN 1946-3 [40]) and the
measuring device TURUS TCA 300 (ISO 8301 [39] and DIN EN 1946-3 [40]) and the measmeasuring parameters (sample thickness, plates temperature difference, mean sample
uring parameters (sample thickness, plates temperature difference, mean sample tempertemperature, etc.) were set before each test. The heat flow meter (HFM) method was used
ature, etc.) were set before each test. The heat flow meter (HFM) method was used (ac(according to [39,40]) to determine the thermal conductivity values. The instrument was
capable of measuring the value for a different range of specimens and was equipped with
one testing chamber to measure, a control system, and an internal single board touchscreen
computer. The testing chamber was equipped with a fixed plate and a mobile top plate.
The top plate could be adjusted based on the specimen thickness from 5 to 100 mm, as
specified by the manufacturer (EN 1946-2 [41]). Either plate could be set as hot or cold
plates. Both hot and cold plates had a workable surface area equal to 300 × 300 mm,
whereas the net surface area of 100 × 100 mm of the central part of each plate was the active
sample measuring zone. The active zones were equipped with one heat flux sensor per
plate, and the HFM were arranged symmetrically and placed at the center of the surface of
the hot and cold plates, respectively (Figure 3).
Each HFM and the plates had their own protection against the heat loss due to lateral
heat flux. Four Peltier devices were used on each side to maintain the temperatures of both
plates and the dissipating heat was extracted with the help of a liquid coolant running
inside the external loop connected to a mini-chiller. Two thermal resistances (PT 1000)
of Class DIN A with a maximum error of 0.08 K (typically better) at 0 ◦ C are presented
to measure the temperature at the center of each plate and the values were used for
controlling the Peltier devices and other purposes. The cool and hot plate temperature
ranges (min/max) were −20/+60 ◦ C and −10/+70 ◦ C, respectively, and depending on the
specimen thickness (5–100 mm), the measured thermal conductivity of the samples could
range from 0.002 to 1.0 W/(m·K).
touchscreen computer. The testing chamber was equipped with a fixed plate and a mobile
top plate. The top plate could be adjusted based on the specimen thickness from 5 to 100
mm, as specified by the manufacturer (EN 1946-2 [41]). Either plate could be set as hot or
cold plates. Both hot and cold plates had a workable surface area equal to 300 × 300 mm,
whereas the net surface area of 100 × 100 mm of the central part of each plate was the
Energies 2021, 14, 3564
active sample measuring zone. The active zones were equipped with one heat flux sensor
per plate, and the HFM were arranged symmetrically and placed at the center of the surface of the hot and cold plates, respectively (Figure 3).
8 of 16
Figure 3. Schematic diagram and the concept of heat flow and temperatures in TAURUS TAC300.
Figure 3. Schematic diagram and the concept of heat flow and temperatures in TAURUS TAC300.
Each HFM and
had their
own
protection
against
heat loss
due
to lateralwith the datThethe
airplates
temperature
and
humidity
close
to thethe
samples
were
measured
heat flux. Four
Peltier
devices
were
used
on
each
side
to
maintain
the
temperatures
alogger Tinytag Ultra 2. The measurement range is from −40 to 85 ◦ C, of
and from 0 to
both plates and
heat was extracted
with at
the1 help
of a liquidThe
coolant
run-conductivity
95%the
UR.dissipating
The measurements
were acquired
min intervals.
thermal
ning inside the
external loop
mini-chiller.
Two thermal
resistances
(PT
measurement
wasconnected
conductedtoinasteady
state conditions,
based
on self-adjusted
temper1000) of Class
DIN
A
with
a
maximum
error
of
0.08
K
(typically
better)
at
0
°C
are
preatures of the plates, which depend on the desired sample mean temperature and plate
sented to measure
the temperature
the center
each plate
and
the values
were
used
temperature
difference. at
Based
on the of
measured
heat
fluxes
by the hot
and
cold plates, the
for controlling
the
Peltier
devices
and
other
purposes.
The
cool
and
hot
plate
temperature
thermal conductivity (λ) value was calculated by the heat flow meter instrument according
ranges (min/max)
were −20/+60
°C and −10/+70 °C, respectively, and depending on the
to Equation
(1).
.
specimen thickness (5–100 mm), the measured thermal
conductivity
W of the samples could
S
λ=Q
.
(1)
range from 0.002 to 1.0 W/(m⋅K).
(t H − tC ) mK
The air temperature
and humidity close to the samples were measured with the dat.
where
flux (W/m2range
); S is is
thefrom
sample
(m);from
tH and
tC 95%
are, respectively,
Q is2.the
alogger Tinytag
Ultra
Theheat
measurement
−40 thickness
to 85 °C, and
0 to
◦
the hot platewere
andacquired
cold plateattemperatures
( C).
UR. The measurements
1 min intervals.
The thermal conductivity measAll testsinhad
a duration
equal to 300
minutes,
much longer
than the time required
urement was conducted
steady
state conditions,
based
on self-adjusted
temperatures
to
achieve
the
steady
state
conditions.
These
were
considered
reached
when the fluctuof the plates, which depend on the desired sample mean temperature and plate temperaations
of
the
thermal
flow
through
the
sample
were
contained
within
the
ture difference. Based on the measured heat fluxes by the hot and cold plates, the thermalresolution of
which generally
an interval
between
180 andto240 minutes,
conductivitythe
(𝜆 instrument,
value was calculated
by theoccurred
heat flowinmeter
instrument
according
depending
on
the
moisture
content
of
the
sample.
The
samples
were
characterized at an
Equation (1).
average temperature of 10 ◦ C, 20 ◦ C, and 30 ◦ C, according to UNI EN 12939 [42], always
𝑆
𝑊 the hot and cold surfaces equal to 20 ◦ C. In
maintaining a temperature
𝜆 𝑄difference between
.
(1)
𝑡
𝑚𝐾
𝑡
order to guarantee a one-dimensional flow through the samples having a surface less than
2 , expanded polystyrene (EPS) protective insulation was used (Figure 4) as
300heat
× 300
mm
2); S is the sample thickness (m); tH and tC are, respectively,
where 𝑄 is the
flux
(W/m
an
uncontrolled
thermal
guard,
thus minimizing the heat losses at the edges.
the hot plate and cold plate temperatures
(°C).
Energies 2021, 14, 3564
of the thermal flow through the sample were contained within the resolution of the instrument, which generally occurred in an interval between 180 and 240 minutes, depending on the moisture content of the sample. The samples were characterized at an average
temperature of 10 °C, 20 °C, and 30 °C, according to UNI EN 12939 [42], always maintaining a temperature difference between the hot and cold surfaces equal to 20 °C. In order to
guarantee a one-dimensional flow through the samples having a surface less than 300 ×
300 mm2, expanded polystyrene (EPS) protective insulation was used (Figure 4) as an uncontrolled thermal guard, thus minimizing the heat losses at the edges.
(a)
9 of 16
(b)
Figure 4. Example of the application of the expanded polystyrene (EPS) to a sample (S05) with 100
Figure 4. (a),
Example
of theofapplication
of the
polystyrene
to2 (b).
a sample (S05)
and example
a sample (S10)
withexpanded
a surface equal
to 300 ×(EPS)
300 mm
× 100 mm2 dimensions
2
with 100 × 100 mm dimensions (a), and example of a sample (S10) with a surface equal to
300 × 300Building
mm2 (b).
3. The Case-Study
In order
to estimate
the possible
energy savings obtainable with the use of the afore3. The
Case-Study
Building
#When
the individual
isestimate
a measured
picture,
AE hasenergy
no way
to
provide
an editable
mentioned
materials
andtothe
conductivity
and
thermal
capacity
values
Inequation
order
theand
possible
savings
obtainable
with
thewhen
use of the aforereplacing traditional
elements,
a
numerical
simulation
was
carried
out
according
to the
version#
mentioned materials and the measured conductivity and thermal capacity
values when
dynamicthis
hourly
described
in the technical
standard
ISO
In particular,
1. download
tool method
fromtraditional
https://mathpix.com,
username
with52016
email
replacing
elements,
aregister
numerical
simulation
was[43].
carried
out according to the
simulations were conducted
using the
dynamicinhourly
simulation
modelISO
implemented
in
method
described
thethe
technical
52016
2. Open the file dynamic
where thehourly
formula
is located
and display
formulastandard
in the center
of the [43]. In particular,
®. The average hourly data (external air temperature,
the commercial
software
Thermolog
simulations were conducted using the dynamic hourly simulation model implemented in
screen
specific humidity,
solar radiation,
speed,®and
and thedata
real(external
conditions
the commercial
softwarewind
Thermolog
. Thedirection)
average hourly
air of
temperature,
3. open
this
tool,
click
the
copy
bottom
the use of the
building
were
used
as
input
data,
specifying
for
each
month
the
number
of
specific humidity, solar radiation, wind speed, and direction) and the real conditions of
4. copy
thisdays
equation
(doofnot
labelwere
and too
much
blank
space
in it)
actual
anduse
hours
ofcopy
air conditioning
system
operation.
the
the
building
used
as input
data,
specifying
for each month the number of
The
case
study
proposed
for
the
analysis
consists
of
a
multistorey
terraced
building
5. then you
can
see
like
below:
the
confidence
color
indicates
recognition
accuracy
of the
actual days and hours of air conditioning system operation.
for
residential
use
(Figure
5),
characterized
by
a
light
envelope
with
opaque
walls
consist-building for
The case
study
proposed
for the analysis
consists
of acolor
multistorey
terraced
equation, the green color
means
it has
high recognition
accuracy,
the red
is opposite
ing the
of 1.5
cm
external
lime
and
plaster,
perforated
bricks
with with
thermal
resistance
residential
(Figure
5), characterized
by
envelope
opaque
walls consisting
6. click
Data
bottom
anduse
copy
thecement
second
row to doc
filea light
0.31 m2K/W,
and
internal
lime and
gypsum
plaster.
The opaque
wallsbricks
make up
46%
of the resistance
of
1.5
cm
external
lime
and
cement
plaster,
perforated
with
thermal
7. then run the new equation
dispersing 0.31
surface
and are
exposed
the and
E–Wgypsum
direction.
m2 K/W,
and
internalinlime
plaster. The opaque walls make up 46% of the
dispersing surface and are exposed in the E–W direction.
Figure 5. The multi-storey building used for numerical simulation and related solar paths.
Energies 2021, 14, 3564
10 of 16
The purpose of the simulation goes beyond obtaining a high energy class or in any
case, a well-defined savings rate, as it is aimed exclusively at verifying the potential energy
savings achievable and its correlation with the reference climatic conditions. For this reason,
replacement of traditional plaster in case 1, using plaster with recycled materials (case 2), or
natural fibers (cases 3–5) was simulated, as detailed in Table 4. The results of the first five
cases were also compared with the corresponding values obtained from case 6, in which
the authors simulated an application of thermal insulation panels in sintered expanded
polystyrene (EPS) on the opaque walls, in order to meet strict national regulations on the
opaque building envelope [44]. The suitable thickness of the EPS layer is the function of
the climatic reference condition: 8 cm for Cagliari (Urif = 0.33 W/m2 K), 7.5 cm for Palermo
(Urif = 0.35 W/m2 K), and 13 cm for Bolzano (Urif = 0.22 W/m2 K).
Table 4. Description of the different cases of study object of the simulation to evaluate the possible energy savings.
Description
Case 1
Case 2
Case 3
Case 4
Case 5
Case 6
Opaque building envelope dispersing towards the outside with traditional plaster (lime
and cement plaster)
Replacement of traditional plaster, using plaster with recycled materials (Opus
signinum and lime putty), same specification as samples S9, S10, S12 and S13 (Table 2)
Replacement of traditional plaster, using plaster made up with natural fibres (sheep’s
wool fibres, lime putty and opus signinum), same specification as samples S11 and S14
(Table 2)
Replacement of traditional plaster, using plaster made up with natural fibres (sheep
wool and thistle fibres), lime putty and opus signum), same specification as samples S5
and S6 (Table 2)
Replacement of traditional plaster with building materials with natural fibres (hemp
shives and clay), same specification as of samples C01 and C02 (Table 2) + 1.5 cm of
clay plaster
Adding thermal insulation panel in sintered expanded polystyrene (EPS) in order to
meet strict national regulations on the opaque building envelope
Thickness (cm)
1.5
1.5
1.5
1.5
1.5 + 3
variable
Finally, in order to evaluate the extent to which plasters with lower thermal conductivity can actually affect the buildings envelope, the simulations were repeated assuming
their use on walls whose elements (e.g., plaster, brickwork, thermal insulation) offer the
maximum allowed U-values according to local regulations.
4. Results and Discussion
4.1. Thermal Characterization of the Analyzed Material
In Table 5, the thermal conductivity at three different temperatures (10, 20, and 30 ◦ C)
for the different analyzed samples and the reference values available in the literature
are reported to allow for comparison. In particular, it is possible to notice how the use
of recycled material (with the tested densities) allows for plasters to be obtained with
conductivity (@20 ◦ C) between 0.430–0.475 W/(m·K), much better than the average values
of traditional plasters using gypsum and/or lime (higher than 0.7 W/(m·K)). The use of
sheep wool inside lime putty allows for a decrease in thermal conductivity from 46% to
62% when thistle fibers are added.
The same fibers guarantee a reduction in the thermal conductivity of the lime putty
and opus signinum blend equal to 37% and 66%, respectively. In particular, the thermal
conductivity was between 0.146–0.272 W/(m·K). It should be noted that these reductions
were obtained with only 3–4% of sheep wool and thistle fiber in the total mixture when
compared to 13% of fibers used by Valenza et al. [25]. Additionally, the use of natural
fibers inside building materials allows for conductivity values to be obtained always
below 0.162 W/(m·K) (@20 ◦ C), with lower values for compounds with recycled materials
(0.107 W/(m·K)). In any case, the measured conductivity was always lower than the ones
available in the literature (Elfordy et al. [24]; El Azhary et al. [29]) for analogous materials.
Finally, it seems that hemp fibers guarantee slightly higher performances (−14%) than
Energies 2021, 14, 3564
11 of 16
the jute ones but, in this regard, the authors will deepen the results through a future test
campaign dedicated exclusively to the use of jute in building materials.
Table 5. Thermal conductivity of the mortar, plastering and insulation materials.
Samples Tested
Sample
Reference Values in the Literature
Thermal Conductivity [W/(m·K)]
Composition
@10 ◦ C
@20 ◦ C
@30 ◦ C
S10
S13
S12
Opus signinum paste
Lime putty and Opus
signinum
Lime putty
Lime putty and Opus
signinum
Traditional Plasters
0.458
0.464
0.471
0.463
0.469
0.476
0.470
0.475
0.479
0.425
0.430
0.436
Thermo-Insulating Retrofitting Plaster with Natural Fibres
S05
S06
S11
S14
Sheep Wool + Thistle
fibres and Lime putty
Sheep Wool + Thistle
fibres, Lime putty and
Opus signinum
Sheep wool and Lime
putty
Sheep Wool, Lime putty
and Opus signinum
S08
C01
Hemp shives and Lime
putty
Hemp shives, Lime putty,
and Opus signinum
Hemp shives and clay
Pure gypsum
plaster
0.70
[19]
Lime &
gypsum
plaster
0.90
[19]
Plasters and Mortars with Natural Fibres
0.172
0.180
0.188
0.139
0.146
0.153
0.248
0.257
0.266
0.265
0.272
0.280
Building Insulation Materials with Natural Fibres
S07
Ref.
@20 ◦ C
Thermo-Insulating Natural Plaster with Recycled Materials
S09
Thermal
Conductivity
[W/(m·K)]
Materials
Used
Sicilian sheep
wool
(washed and
unwashed) +
Cement
0.09–0.11 (with
46% wool
1–20 mm)
[28]
0.15–0.25 (with
13% wool
1–20 mm)
Building Materials with Natural Fibres
0.096
0.109
0.122
0.093
0.107
0.121
0.124
0.139
0.151
Lime and
hemp
concrete
(“hempcrete”)
Straw and
clay
0.179–0.485
[27]
0.260–0.508
[25]
The results obtained for average temperatures (10 and 30 ◦ C) of the specimens different
to the traditional ones also showed the same trends. Based on these results, it is possible to
hypothesize with sufficient accuracy an almost linear dependence of thermal conductivity
with temperature, with a general slope coefficient between 0.0006–0.0014 W/(m·K).
4.2. Influence of the Moisture Content
In order to verify the influence of the moisture content on the analyzed materials,
repeated measurements of the thermal conductivity were carried out on three samples
during their entire drying period. For example, in Figure 6, the decrease in weight (in
blue) and the contextual measurement of thermal conductivity (in red) for sample S14
is reported. The measurements were started after an initial drying period of seven days
as above-mentioned, and stopped when the variations in mass of the sample were less
than the measurement uncertainty for a period of at least 48 hours. In all tests, the
conductivity decreased as the drying of the sample progressed, showing an average
conductivity decrease of 16.3% against a mass decrease on average close to 5.5%.
during their entire drying period. For example, in Figure 6, the decrease in weight (in
blue) and the contextual measurement of thermal conductivity (in red) for sample S14 is
reported. The measurements were started after an initial drying period of seven days as
above-mentioned, and stopped when the variations in mass of the sample were less than
the measurement uncertainty for a period of at least 48 hours. In all tests, the conductivity
12 of 16
decreased as the drying of the sample progressed, showing an average conductivity decrease of 16.3% against a mass decrease on average close to 5.5%.
Thermal conductivity [W/(m K)]
0.430
Thermal conductivity [W/mK]
0.410
Mass [kg]
0.25
0.24
0.390
0.23
0.370
0.22
<------------------->
Initial drying
period
0.350
0.330
0.310
0.21
0.20
0.19
0.290
0.18
0.270
0.17
0.250
0.16
Mass [kg]
Energies 2021, 14, 3564
0.15
0.230
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
[days]
Figure6.6.Effect
Effectof
ofwater
watercontent
contenton
onthermal
thermalconductivity.
conductivity.
Figure
4.3. Energy Performance Analysis Applied to the Case Study
4.3. Energy Performance Analysis Applied to the Case Study
Table 6 shows the results obtained for the case study building. In particular, the differTable 6 showsheat
the loss
results
obtained(H
for )the
case study building. In particular, the difent “transmission
coefficient”
tr values and the corresponding useful “thermal
H
tr) values and the corresponding useful “therferent
“transmission
heat
loss
coefficient”
(
energy requirements” EPH,nd (for winter air conditioning) and EPC,nd (for summer air conmal
energyare
requirements”
PH,nd (for winter air conditioning) and EPC,nd (for summer air
ditioning)
represented. EWithin
the table, both absolute values and relative percentage
conditioning)
are
represented.
Within
the table,
bothfor
absolute
values and
relative percentdifferences with respect to case 1 are shown
to allow
an immediate
comparison
between
age
differences
with
respect
to
case
1
are
shown
to
allow
for
an
immediate
comparison
the analyzed solutions for two different semi-continental (Bolzano) and Mediterranean
between
analyzed
solutions
for two different semi-continental (Bolzano) and Mediterclimatic the
conditions
(Cagliari
e Palermo).
ranean climatic conditions (Cagliari e Palermo).
mentioned,
thecoefficient
aim was not
obtain
a highenergy
energyrequirements
class or a well-defined
TableAs
6. already
Transmission
heat loss
andto
useful
thermal
for different
savings
to verify
the potential
materialsrate,
and but
reference
climatic
conditions.energy savings achievable and its correlation with
the reference climatic conditions. It is possible to note how the addition of natural fibers
Casein1 the performance
Case 2
Case
3
Case 4of theCase
5
Case 6
always led to an improvement
characteristics
building
envelope.
Due to the
of the material
(1.5
cm), the reduction
in259.73
the Htr
Htr reduced
[W/K] thickness
302.03
294.24 considered
294.24
288.56
279.07
(%)
−2.6%
−2.6%
−4.5%
−7.6%
14.0%
coefficient could
be quantified between
2.6% and
7.6%, respectively,
for
the use−of
opus
Cagliari
EPH,nd [kWh/m2 ]
(%)
EPC,nd [kWh/m2 ]
(%)
83.10
5.51
80.62
−3.0%
5.70
3.4%
78.8
−5.2%
5.90
7.1%
76.61
−7.8%
6.07
10.2%
78.10
−6.0%
5.95
8.0%
64.04
−22.9%
5.84
6.0%
167.79
−2.8%
-
164.20
−4.9%
-
159.89
−7.4%
-
162.83
−5.7%
-
130.69
−24.3%
0.11
-
52.53
−3.2%
22.48
−0.2%
51.26
−5.5%
22.44
−0.4%
49.73
−8.4%
22.41
−0.5%
50.77
−6.4%
22.43
−0.4%
41.15
−24.2%
22.30
−1.0%
Bolzano
EPH,nd [kWh/m2 ]
(%)
EPC,nd [kWh/m2 ]
(%)
172.70
-
Palermo
EPH,nd [kWh/m2 ]
(%)
EPC,nd [kWh/m2 ]
(%)
54.27
22.53
As already mentioned, the aim was not to obtain a high energy class or a well-defined
savings rate, but to verify the potential energy savings achievable and its correlation with
the reference climatic conditions. It is possible to note how the addition of natural fibers
always led to an improvement in the performance characteristics of the building envelope.
Due to the reduced thickness of the material considered (1.5 cm), the reduction in the Htr
Energies 2021, 14, 3564
13 of 16
coefficient could be quantified between 2.6% and 7.6%, respectively, for the use of opus
signinum (case 2) and hemp (case 5) in the mixture. With these thicknesses, their effect was
an order of magnitude lower than that obtained in case 6, where the legal requirements
were fulfilled with an EPS thermal coat of an appropriate thickness. In this last case, in
all three reference climatic conditions, there was an improvement in EPHn,d equal to or
greater than 23%, even if for Bolzano, the addition of a thermal coating involved a slight
increase in the thermal energy requirements needed for summer air conditioning. With
similar percentages, the useful thermal energy requirements for heating also decreased
in quantities ranging from 3% for Cagliari (with the use of opus signinum) and 8.4% for
Palermo (with the use of hemp and clay). On the other hand, it should be noted that the
light structure and the low thermal capacity of the analyzed materials did not entail equally
significant variations in the energy requirements for summer air conditioning. Where
appreciable (Palermo and Cagliari), this was variable in modest percentages (Palermo)
or even increased for the city of Cagliari from 3.4% to 10.2%. Finally, Table 7 shows
the comparisons in terms of EPH,nd when recycled materials (cases from 2 to 5) are used
on walls whose elements (e.g., plaster, brickwork, thermal insulation) already offer the
maximum allowed U-values according to local regulations. Case 1 is the reference one
where traditional plaster was used. As expected, the influence of plasters with recycled
materials on walls that already meet the regulatory requirements was negligible (<1%) in
both analyzed climates. However, it is important to underline that when the materials
analyzed in this paper and the traditional ones were compared, the real innovative and
rewarding aspect is not represented by the achievable energy saving (it cannot be otherwise,
given the thicknesses used), but in the possibility of using locally produced natural and
waste/recycled products with a lower environmental impact. In order to reinforce this
peculiarity, the authors integrated the study with a life cycle assessment (LCA) in order to
evaluate the environmental footprint along their entire life cycle.
Table 7. Useful thermal energy requirements EPH,nd on walls that already meet the regulatory
requirements.
Cagliari
Bolzano
Palermo
EPH,nd
[kWh/m2 ]
(%)
EPH,nd
[kWh/m2 ]
(%)
EPH,nd
[kWh/m2 ]
(%)
Reference Case
Case 2
Case 3
Case 4
Case 5
64.04
64
63.95
63.88
63.47
−0.1%
−0.1%
−0.2%
−0.9%
131.53
130.36
130.29
129.82
0.90%
0%
−0.1%
−0.4%
41.19
41.15
41.09
40.93
0.00%
−0.1%
−0.3%
−0.7%
130.38
41.21
5. Conclusions
In this paper, the authors report the results of an experimental investigation on innovative materials characterized by the use of locally produced natural and waste/recycled
products that are able to provide good thermal performances while also having a lower
environmental impact.
A total of twelve samples were prepared using Sardinian zero-km locally available
raw materials: wool fibers from mattress stuffing, couches, and chair padding; hemp
shives directly from the hemp stalks; jute fiber from recycled jute bags; opus signinum
from crushed tiles, and clay from local extraction in central Sardinia. The use of recycled
materials allowed us to obtain plasters with a conductivity (@20 ◦ C) about 32% lower than
traditional plasters using gypsum and/or lime. The use of natural fibers (sheep wool and
thistle fibers) inside lime putty allowed for a decrease in thermal conductivity of up to 62%.
Energies 2021, 14, 3564
14 of 16
By means of a numerical simulation, it was possible to verify that the addition of
natural fibers always leads to an improvement in the energy performance of the building
envelope during the winter season compared to traditional plaster. The positive effect
induced by their use obviously decreases in percentage on already performing walls until it
almost disappears for walls that comply with the current stringent regulatory requirements
for new buildings. On the other hand, significant decrease in installation and in the
environmental costs associated with their production could still make their use more
suitable for new and existing buildings.
Finally, the use of jute inside building elements to realize insulating panels, even if
not with the same performances obtained with the hemp shivers, shows promising results,
with conductivity values always lower than 0.162 W/(m·K). In this regard, more accurate
values could be highlighted at the end of the experimental campaign that the authors will
carry out on specific products made with the use of jute fibers.
Author Contributions: Study conception and design: A.F. and M.D.; Acquisition, analysis, and
interpretation of data: A.M. and C.C.M.; Drafting of manuscript: A.M., A.F., A.P. and L.C.; Critical
revision: all authors. All authors have read and agreed to the published version of the manuscript.
Funding: This work has been developed under the projects “PLES”, financed with funds “POR
FESR 2014/2020—ASSE PRIORITARIO I “RICERCA SCIENTIFICA, SVILUPPO TECNOLOGICO E
INNOVAZIONE” (grant number F21B17000750005).
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Acknowledgments: Authors would like to acknowledge the support of Costanzo Salis for providing
the raw materials.
Conflicts of Interest: The authors declare no conflict of interest.
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