- Email: [email protected]
Thermal insulating plaster as a solution for refurbishing historic building envelopes: First experimental results
Accepted Manuscript Title: Thermal insulating plaster as a solution for refurbishing historic building envelopes: first experimental results Author: Lorenza Bianco Valentina Serra Stefano Fantucci Marco Dutto Marco Massolino PII: DOI: Reference:
S0378-7788(14)00941-4 http://dx.doi.org/doi:10.1016/j.enbuild.2014.11.016 ENB 5479
To appear in:
ENB
Received date: Accepted date:
15-10-2014 1-11-2014
Please cite this article as: L. Bianco, V. Serra, S. Fantucci, M. Dutto, M. Massolino, Thermal insulating plaster as a solution for refurbishing historic building envelopes: first experimental results, Energy and Buildings (2014), http://dx.doi.org/10.1016/j.enbuild.2014.11.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
*Manuscript
Thermal insulating plaster as a solution for refurbishing historic building envelopes: first experimental results Lorenza Bianco1, Valentina Serra1*, Stefano Fantucci1, Marco Dutto2, Marco Massolino2 1
Department of Energy, Politecnico di Torino, TEBE Research Group, Turin, Italy
2
Vimark srl - Peveragno (Cuneo), Italy
ip t
Corresponding author* Valentina Serra, Politecnico di Torino, Dept. of Energy, Corso Duca degli Abruzzi 24, 10129 Torino, 0039110904431, [email protected]
cr
ABSTRACT
us
In Italy, historic buildings constitute 20% of the built environment. Although historic buildings are usually excluded from the obligation of adopting specific energy standard, energy related aspects should be
an
nevertheless faced and managed in order to exploit the building “usability” potential, to attain indoor environmental quality and energy efficiency conditions. The energy refurbishment of this kind of building is,
M
however, a very complex matter that leads to a number of question concerning buildings conservation and valorisation aspects. A non invasive technique, that is, the application of thermal plaster to the internal side of
ed
a building envelope, has been investigated in this paper. Thanks to its relatively easy installation and reversibility, thermal insulating plaster seems to represent a very interesting solution as it is able to offer a
ce pt
good compromise between energy and conservation aspects. The aim of this work is to present a thermal, vegetal based insulating plaster, which has recently been developed within a research project, and to investigate its potential to reduce the heat flux exchanged through
Ac
the vertical envelope of historic buildings, by means of measurements carried out in both the laboratory and in the field, for a real case application. KEYWORDS thermal insulating plaster, building envelope, historic building, built heritage, energy refurbishment, retrofitting. 1. INTRODUCTION The refurbishment of existing buildings is a crucial point for the achievement of the energy and climate objectives of the European Union (EU) for 2020 and 2050. The energy performance of existing buildings is still very poor, and the construction sector is responsible, on average, for 35% of the energy consumption in Europe and in Italy [1]. The problem is made, even more complex in Italy, by the
Page 1 of 24
remarked presence of historic buildings, which constitute 20% of the existing building stock (2 out of 10 buildings were built before 1919) [2]. Passing from energy related aspects to the cultural ones, according to the Italian Constitution (art.9), historic buildings should be preserved and protected because they constitute a source of knowledge of the architectural history of the country. Consequently, the strategy concerning the protection of historic
ip t
buildings must be enhanced, and it could be more easily implemented if buildings continue to have a function and a role, as theorized by Annoni in 1946 [3]. Specific maintenance interventions, are therefore
cr
needed to refurbish the buildings from the energy point of view. Although historic buildings are usually
us
excluded from the obligation of adopting specific energy standards, energy related aspects should be faced and managed in order to exploit the building “usability” potential, so as to create acceptable indoor
an
environmental quality and energy efficiency conditions.
The energy refurbishment of this kind of building is a very complex matter that leads to a number of
M
question concerning conservation and valorisation of the building aspects and which require “one case at a time” approach [3], when deciding how and where to intervene on a building.
ed
A literature review has shown, that a qualitative and quantitative approach to the energy and sustainability of heritage buildings needs to be applied [4]. Furthermore, the lack of a methodology, technologies and
ce pt
knowledge on historic building retrofitting has been observed. Till now, only a few experimental and modelling activity researches have been conducted on this topic [5,6]. One study has recently presented a methodology, based on MCDM analysis (multiple-criteria decision-making), to select the best solution for
Ac
the internal insulation of a brick wall in a historic building [5]. Thanks to the relatively easy installation and reversibility, thermal insulating plaster seems to represent a very interesting solution, as it is able to offer a good compromise between energy and conservation aspects for those buildings where it can be applied (i.e. no frescoed walls). The first results of a research project, aimed at developing new kinds of plaster and insulation materials with low embodied energy, are presented. In this work, the analysis has focused on a new thermal, vegetal based plaster, developed specifically for internal insulation. In particular, the study here presented deals with its applicability to the internal side of an existing historical building envelope under refurbishment, and assesses the impact on the thermal flux reduction.
Page 2 of 24
The thermal insulating plaster has been tested in the laboratory to assess its thermal properties and in a real historic building, to investigate its potential to reduce the heat flux exchanged through the vertical envelope on which it has been applied. 2. THERMAL INSULATING PLASTER Plaster has been used for thousands of years as constructive element in buildings, especially in Europe. The
ip t
versatility of this material allows it to be both used internally and externally, with the possibility of applying rendering or plastering mortar to different substrates, constructions and compositions. Thermal insulating
cr
plaster represents one of the possible solutions that can be adopted to face energy related problems in
us
existing and historic buildings. The workability of thermal plaster is very similar to that of traditional plaster, as it can be used on non-aligned, out of square, or even on curved supports. Thermal insulating plaster is in
an
fact flexible and can be suitable for any architectural or design solution. Moreover, thermal insulating plaster is characterised by a high water vapour diffusion coefficient, with a water vapour resistance factor (µ value)
M
of between 5 and 15. For this reason, the application of this technology to existing walls is possible for envelopes affected by capillary rising damp, a problem which is very often present in historic buildings.
ed
Thermal insulating plaster has been studied not only to be a finishing or a protection layer of the walls, but also to improve their thermal resistance. These special kinds of plaster are characterised by thermal
ce pt
conductivity values that are more than ten times lower than traditional plaster (standard lime plaster 0.7 W/(mK)) and they are divided into two categories: plaster with natural binders (natural hydraulic lime) and plaster with cement or artificial binders. These types of plaster are usually pre-mixed and ready to use and
Ac
are made with Light Weight Aggregates (LWA), such as cork, clay, perlite, pearls of expanded polystyrene, expanded glass, etc. LWA are able to significantly improve the thermal and acoustical insulation performances of the component. Additionally, the weight of the component is noticeably reduced, compared to traditional ones [7].
New kinds of thermal insulating plaster are still being studied to reduce their thickness and to improve their thermal conductivity. Research is moving towards new aggregates, that is, innovative or natural materials. High-tech solutions, such as aerogel or phase change material (PCM) based plaster, are also being investigated.
Page 3 of 24
In this paper, the results related to traditional and advanced materials for thermal plaster are presented, with particular focus on the thermal properties of a vegetal based plaster. Vegetal aggregate materials, derived from corncobs, were added to a natural Wasselonne hydraulic lime and expanded silica (perlite), and the resulting plaster was tested through a laboratory analysis and in field measurements. The particle size distribution of the ingredients was studied in the laboratory to obtain the best combination from the physical,
ip t
mechanical and thermal points of view. Wasselonne lime is a Natural Hydraulic Lime (NHL 2, according to the EN 459-1:2010 standard [8]) that has been extracted since 1932 in the Alsace region, France, and it
cr
constitutes a significant percentage of the final product. The natural aggregate in these prototypes was 43%
us
(33% corncobs and 10% of dried expanded silica) and it played a double role: firstly, it contributed to an improvement in the insulation of the plaster by exploiting a waste material (i.e. the corncobs) and, secondly,
an
the mechanical properties of the plaster were improved and the risk of cracking was hence reduced. Furthermore, the natural binder gave a high water vapour diffusion coefficient to the plaster (that is, higher
wall using a plastering machine (Figs. 1a and 1b).
M
than cement binders). Application tests were carried out by spraying the thermal insulating plaster onto a test
ed
The results have showed that this technology is capable of supporting greater thicknesses of thermal insulating plaster (above 10 cm) than traditional insulating plaster. The same result could only be achieved
ce pt
using a traditional plaster through the repeated application of thin plaster layers onto its support with the consequent risk of cracking. The sample that passed the first mechanical test and presented the best performance was named VGT_04, and the results related to this sample are hereafter presented. The results
Ac
concerning long - term decay and the marcescence and oxidation processes are not yet available, but these important aspects are currently under investigation. Furthermore, on the basis of the ISO 14040:2006 standard [9], a life cycle analysis is also being conducted. 3. THE MEASUREMENTS 3.1 Laboratory measurement methodology Laboratory measurements have been performed to assess the equivalent thermal conductivity of the thermal plaster samples (10 cm thickness and 60x60 cm size, as shown in Figure 2a). A set of experimental measurements was carried out with heat flow meter apparatus, in accordance with the EN 12667:2001 international standard [10]. The apparatus, a Lasercomp FOX600, consists of a single sample, heat flow
Page 4 of 24
meter with a guarded ring equipped with two plates containing heat flow meters placed above and below the sample (Fig. 2b). Specifications details of the equipment are given in Table 1. The instrument was designed and set up in accordance with the ASTMC518, 1991 [11] standard and it was calibrated with “1450b NIST SRM” calibration reference samples and an EPS sample (expanded polystyrene). All the samples were previously tested and certified by NIST. In order to avoid any additional
ip t
surface resistances, due to the sample discontinuity, all the specimens were sandwiched between two rubber 3 mm sheets with a thermal conductivity of 0.073 W/(mK) at 10 °C. The uncertainty of the measured thermal
cr
conductivities were determined for each measurement in accordance with ENV 13005:1999 [12]. The
us
resulting uncertainty values were within ±2%, according to EN 12667:2001 [10] (annex B), including the additional uncertainty caused by subtracting the resistance of the rubber sheets.
an
Laboratory measurements were performed on two different samples (A and B) of the same thermal plaster (VGT_04 with natural Wasselonne hydraulic lime and vegetal aggregate materials). Before the tests, both
M
specimens were dried to constant mass in a ventilated oven for 48 h at 60°C to determine their mass. The relative loss in mass was calculated comparing the mass of the samples before and after the drying cycle. The
ed
tests were carried out at three different mean temperatures: 10, 25 and 40 °C, respectively, with a temperature difference of 20 °C, to minimize temperature - difference measurement errors.
ce pt
As is known the measurement principle is to create a constant temperature difference between the upper plate and the lower plate, and to measure the specific heat flux and surface temperatures in steady state conditions. The equivalent thermal conductivity [W/ (mK)] is then calculated using Equation 1, where s is
Ac
the sample thickness [m], q is the specific heat flux [W/m2] and ∆ts is the temperature difference between the two faces of the plate [°C].
eq (s q ) / t s [W/m°C] (1)
3.2. Laboratory measurement results The sample specifications are shown in Table 2. Samples A and B differ mainly as far as the density is concerned: sample A presents a higher density than sample B for both humid and dried samples. The thermal conductivity of the two different samples is reported in Table 3. In Figure 3, which shows the equivalent thermal conductivity vs. average temperature of the plates, it is possible to observe the influence of the water content on the thermal conductivity. Page 5 of 24
Both samples demonstrate quasi-linear behaviour: the difference between the dry and the humid samples is between 8% and 17% for sample A, and between 3% and 4% for sample B, depending on the set-point temperatures. The divergence between samples A and B was due to their different water contents. The experimental results show that vegetal aggregates have a great potential to reduce the thermal conductivity of plaster, compared to traditional cement thermal plaster with lime. From an analysis of the
ip t
results merges that, the thermal conductivity of the thermal insulating plaster (VGT_04) is 0.08 – 0.13 W/(mK) range while the reference sample is the 0.25-0.27 W/(mK) range. This means that samples A and B
cr
are 2.5 and 3 times more insulating than the reference sample. It should be emphasized that the results
us
achieved with these natural aggregates are in line with the literature values [13] obtained for different aggregates (i.e EPS, cork).
an
3.3. In field measurements: the case study
In order to investigate the performance of the analysed technology on an actual building, a set of
M
measurements was performed in a real application on the building envelope of a historic building under refurbishment in Turin, the ex Albergo di Virtù, 1580 (Fig.4). This historic building, which has a
ed
monumental value for the city of Turin, will become to a top category hotel, reinstating its original function. The vertical opaque envelope of the building presents a 500 mm thick and heterogeneous (brick and stone)
ce pt
wall. Thanks to the involvement of the contractor in the project, it was possible during the refurbishment to use two identical rooms with the same South - East orientation as test rooms. A 60 mm layer of thermal insulating plaster, made up of Wasselonne natural hydraulic lime and vegetal aggregate materials (VGT_04),
Ac
was applied to the wall of a room facing the external environment (Fig.5a); in the other room, the same external reference wall was left without any internal finishing (Fig. 5b). The air temperature was controlled in both rooms through electric heaters, with a temperature set point of 23°C. The thermo-physical behaviour and the energy performance of the vertical envelope was assessed by means of the continuous measurements of the heat flux, surface temperature and air temperature (according to ISO 9869-1:2014) [14]. The position of the probes was decided after an infrared image campaign of the investigated walls through a NEC Thermo Tracer (TH9100 MV/WV). In this way, the sensors were positioned in homogenous and representative areas of the wall (avoiding thermal bridges and discontinuity of the material). Heat flux meters, which had previously been tested in the laboratory, were placed on the
Page 6 of 24
internal surface of both walls. The internal and external surface temperatures and the indoor and outdoor air temperatures were measured by means of thermocouples (TT-types, previously calibrated in the laboratory). The instruments were connected to two data loggers placed in each test room, which retrieved data every 15 minutes. Hourly values were then calculated off-line for the data elaboration. The thermal performance of the wall with VGT_04 was established, on one hand, through an assessment of
ip t
the thermal transmittance and, on the other hand, through the calculation of the daily transmitted energy. The equivalent thermal transmittance was evaluated through the progressive average methodology, where the
cr
average values, of the specific heat flux (in W/m2) and the temperature differences between internal and
(Q / A) n (t s ) n
[W/m2°C] (2)
an
U*
us
external air, were used instead of the instantaneous values (ISO 9869 1994) [14], according to equation (2).
The total daily transmitted energy e24 (in Wh/m2) is defined as the energy transferred through the façade on a
M
daily basis. The convention used during the measurements was that a negative value of heat flux meant heat losses and a positive one meant heat gains. The total daily energy (equation 3) was then obtained from the
indoor surface of the façade.
ed
integral over the 24 h (from 00 am to 00 pm of the following day) of the surface heat flux exchanged on the
24:00
ce pt
e24
(q )dt [Wh/m ] (3) 2
00:00
3.4. Infield measurement results
Ac
The first step of the infield measurement was an infrared image campaign. It was necessary to verify the homogeneity of the walls in order to evaluate where to position the sensors. The infrared and visible images of the two tested walls are presented in Figure 6. The surface temperature is slightly lower in the lower part of the plastered wall, on the floor and below the window, due to thermal bridges and discontinuity of the material. The surface temperature of the reference wall is affected to a great extent by the finishing discontinuity. A central position, where the node with the lateral partition wall did not influence the surface temperatures, was chosen for the heat flux meter. The daily energy of a seven days campaign, characterised by a rather high temperature difference between the indoor and the outdoor environment, is plotted in Figure 7. Boundary conditions, during the selected
Page 7 of 24
days, were similar in the two test rooms. The average air temperature in the room with the thermal plaster (VGT_04) in the selected days was between 22.6 and 23.6 °C, while an average daily indoor air temperature of between 22.5 and 22.8 °C was measured in the reference room. A minimum average daily outdoor air temperature of 11.7 and a maximum value of 17.7 °C were measured in the considered days. In Figure 7, it is possible to notice that the energy losses through the reference wall are always higher than
ip t
those through the wall with the thermal plaster. The measured heat flux values are negative for each day. Since the outdoor air temperature was always lower than the indoor air temperature, the daily energy that
cr
crossed the reference wall was between 20% (day 3) and 41% (day 7) higher than the daily energy through
us
the VGT_04 wall. As the boundary condition and the wall structure were the same, it is possible to state that the difference monitored between the two test rooms was due to the presence of the thermal plaster layer.
an
In order to have a more complete picture of the energy performance of the tested wall, a new measurement campaign was carried out in a more representative period, in order to collect enough data to assess the
M
thermal conductance/transmittance of the wall with the average method. The data collected in this first campaign, which was performed in a cold April (very cold nights but also sunny days) shows highly
transmittance in a proper way.
ed
dynamic behaviour of the wall, and it was therefore not possible to define the stationary equivalent thermal
ce pt
The equivalent thermal transmittance of the plastered wall was 0.56 W/(m2K), as shown in Figure 8, which means a thermal transmittance of the bare wall of about 0.8 W/(m2K), calculated assuming the thermal resistance of the thermal plaster as resulting from the ratio of the measured value of the thermal conductivity
Ac
to the real applied thickness. Unfortunately, it was not possible to measure the bare wall in the other test room since it was under refurbishment during the second measurement period. The comparison between the two values confirm that 6 cm of VGT_04 thermal plaster can reduce heat loss by about 30%. 4. CONCLUSIONS
In this paper, thermal insulating plaster has been investigated as a possible option for historic building refurbishment. A new thermal insulating plaster was obtained adding to the natural hydraulic lime of Wasselonne, vegetal aggregate materials deriving from the waste of the corn production, which lend higher mechanical properties to the plaster and allows higher layer thicknesses.
Page 8 of 24
Results concerning laboratory measurement and the monitoring campaign in a real application on the building envelope of a historic building located in Turin are discussed. The low thermal conductivity of the new material, which is 2.5/3 times lower than conventional plaster, has led to a significant reduction in the energy that crosses the wall (about 20% - 40%). Other analyses are ongoing with the aim of further diminishing this value. However, its good hygrothermal
ip t
behaviour and its very low embodied energy already make it a real competitive and marketable solution for the retrofitting of existing buildings. Future work is necessary in order to evaluate the decay of the
cr
technology in long-term application.
Wh/m2 W/m°C W/m°C
q Q
W/m2
specific heat flux heat flux
M
m thickness °C surface temperature difference 2 W/m °C equivalent thermal transmittance
ACKNOWLEDGEMENTS
ed
s Δts U*
W
daily energy equivalent thermal conductivity thermal conductivity
an
e24 λeq λ
us
NOMENCLATURE
ce pt
The research was developed in the framework of the POLIGHT project “SI2 – Sistemi isolanti innovativi”, funded by the Regione Piemonte. The project was developed in co-operation with DAD_Politecnico di Torino, VIMARK s.r.l., AGRINDUSTRIA s.n.c., CLUSTER s.r.l., ARTI E MESTIERI and ATC Torino-
Ac
Agenzia Territoriale per la casa della provincia di Torino. REFERENCES
[1] Strategia Energetica Nazionale: per un’energia più competitiva e sostenibile, marzo 2013, approved by DM 8 march 2013. [2] ISTAT 2013. Rapporto Bes. Il benessere equo e sostenibile in Italia, capitolo 09, Il paesaggio e patrimonio culturale, march 2013. [3] A. Annoni, Scienza ed arte del restauro architettonico. Idee ed esempi, Edizioni Artistiche Framar, Milano, (1946), p. 14.
Page 9 of 24
[4] K. Fabbri, Energy incidence of historic building: Leaving no stone unturned, Journal of Cultural Heritage, 14s (2013) e25–e27. [5] J. Zagorskas, E. K. Zavadskas, Z. Turskis, M. Burinskiene, A. Blumberga, D. Blumbergaba, Thermal insulation alternatives of historic brick buildings in Baltic Sea Region, Energy and Buildings, 78 (2014) 3542.
ip t
[6] F. Ascione, F. De Rossi, G.P. Vanoli, Energy retrofit of historical buildings: theoretical and experimental investigations for the modelling of reliable performance scenarios. Energy and buildings, 43 (2011) 1925-
cr
1936.
us
[7] L. M. Silva, R. A. Ribeiro, J. A. Labrincha, V. M. Ferreira,. Role of lightweight fillers on the properties of a mixed-binder mortar. Cement & Concrete Composites, 32 (2010) 19-24.
an
[8] EN 459-1. 2010 - Building lime. Part 1: Definitions, specifications and conformity criteria. [9] ISO 14040. 2006 - Environmental management - Life cycle assessment - Principles and framework.
M
[10] EN 12667. 2001 - Thermal performance of building materials and products - Determination of thermal resistance by means of guarded hot plate and heat flow meter methods - Products of high and medium
ed
thermal resistance. [11] ASTM C518. 1991. Test Method for Steady-State Heat Flux Measurements and Thermal Transmission
ce pt
Properties by Means of the Heat Flow Meter Apparatus. [12] ENV 13005. 1999. Guide to the expression of uncertainty in measurement. [13] F. Favoino, M. Perino, V. Serra, Improving thermal performance of plasters by means of recycled and
Ac
phase change materials. Proceedings, in: Healthy Buildings 2012, Brisbane (AU), 8 - 12 July 2012, 1-2. [14] ISO 9869. 1994. Thermal insulation - Building elements - In-situ measurement of thermal resistance and thermal transmittance.
Page 10 of 24
Table(s) with Caption(s)
Table 1, Experimental apparatus (hot plate) specifications ~ 0.01 - 0.2 ~1 ~ 0.5 ~ ± 0.03 ~ ± 0.025 ~ 610 x 610 254 x 254 ~ 203
W/(mK) % % °C mm mm mm mm
Table 2, Samples of VGT_04 specification Sample size
[kg/m3] 507 496 402 400
[mm] 600x600 600x600 300x300 300x300
Sample thickness [mm] 100 100 50 50
us
Density
M
Sample “A” Sample“A dry” Sample “B” Sample“B dry”
Time of drying [h] 0 48 0 48
an
Name
cr
ip t
Thermal conductivity range Accuracy Reproducibility Temperature control stability Thickness measurement precision Maximum sample size Actual measuring area Maximum sample thickness
Sample B λeq λeq.dry [W/(mK)] [W/(mK)] 0.092 0.088 0.089 0.086 0.086 0.083
ce pt
Sample A λeq λeq.dry [W/(mK)] [W/(mK)] 0.126 0.105 0.115 0.100 0.107 0.098
Δλ [%] ±2% ±2% ±2%
Ac
taverage [°C] 40.00 25.00 10.00
ed
Table 3. Sample VGT_04 A and VGT_04 B thermal equivalent conductivity results for Δt=20°C
Page 11 of 24
List of Figure Captions
List of figure captions Figure 1. a) Evaluation of the possible thickness for thermal insulating plaster applications (left) b), Mechanical application of the thermal insulating plaster (right) Figure 2. a) Thermal plaster sample (left), b) Experimental apparatus: hot plate (right)
ip t
Figure 3. Experimental result: thermal conductivity vs average temperature of the plates for samples A and B of VGT 04, for both humid and dry conditions, and a reference cement thermal plaster
Figure 5. a) Tested wall with the thermal plaster, b) Reference tested wall
cr
Figure 4, Piazza Carlina Turin, ex Albergo di Virtù during the refurbishment
us
Figure 6. Infrared images: test room with the thermal insulating plaster VGT_04 (upper), and the bare wall of
an
the reference test room (lower)
Figure 7. Daily energy through the reference wall and the thermal insulating plaster wall
Ac
ce pt
ed
M
Figure 8. Equivalent thermal transmittance of the tested wall with thermal plaster VGT_04 (b)
Page 12 of 24
ed
pt
ce
Ac M
an
us
cr
i
1a
Page 13 of 24
ed
pt
ce
Ac M
an
us
cr
i
1b
Page 14 of 24
d
te
Ac ce p us
an
M
cr
ip t
2a
Page 15 of 24
d
te
Ac ce p us
an
M
cr
ip t
2b
Page 16 of 24
ed
pt
ce
Ac M
an
us
cr
i
3
Page 17 of 24
ed
pt
ce
Ac M
an
us
cr
i
4
Page 18 of 24
d
te
Ac ce p us
an
M
cr
ip t
5a
Page 19 of 24
ed
pt
ce
Ac M
an
us
cr
i
5b
Page 20 of 24
ed
pt
ce
Ac M
an
us
cr
i
6
Page 21 of 24
ed
pt
ce
Ac M
an
us
cr
i
7
Page 22 of 24
ed
pt
ce
Ac M
an
us
cr
i
8
Page 23 of 24
*Highlights (for review)
-
Thermal insulating plaster is a possible option for historic building refurbishment
-
A new thermal insulating plaster vegetal based is investigated in the laboratory and infield on a real historic building
-
Vegetal aggregate materials lend higher mechanical properties to the plaster and allows higher layer thicknesses
ip t
The low thermal conductivity of the new material led to a significant reduction in the energy that
ce pt
ed
M
an
us
cr
crosses the wall
Ac
-
Page 24 of 24
S0378-7788(14)00941-4 http://dx.doi.org/doi:10.1016/j.enbuild.2014.11.016 ENB 5479
To appear in:
ENB
Received date: Accepted date:
15-10-2014 1-11-2014
Please cite this article as: L. Bianco, V. Serra, S. Fantucci, M. Dutto, M. Massolino, Thermal insulating plaster as a solution for refurbishing historic building envelopes: first experimental results, Energy and Buildings (2014), http://dx.doi.org/10.1016/j.enbuild.2014.11.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
*Manuscript
Thermal insulating plaster as a solution for refurbishing historic building envelopes: first experimental results Lorenza Bianco1, Valentina Serra1*, Stefano Fantucci1, Marco Dutto2, Marco Massolino2 1
Department of Energy, Politecnico di Torino, TEBE Research Group, Turin, Italy
2
Vimark srl - Peveragno (Cuneo), Italy
ip t
Corresponding author* Valentina Serra, Politecnico di Torino, Dept. of Energy, Corso Duca degli Abruzzi 24, 10129 Torino, 0039110904431, [email protected]
cr
ABSTRACT
us
In Italy, historic buildings constitute 20% of the built environment. Although historic buildings are usually excluded from the obligation of adopting specific energy standard, energy related aspects should be
an
nevertheless faced and managed in order to exploit the building “usability” potential, to attain indoor environmental quality and energy efficiency conditions. The energy refurbishment of this kind of building is,
M
however, a very complex matter that leads to a number of question concerning buildings conservation and valorisation aspects. A non invasive technique, that is, the application of thermal plaster to the internal side of
ed
a building envelope, has been investigated in this paper. Thanks to its relatively easy installation and reversibility, thermal insulating plaster seems to represent a very interesting solution as it is able to offer a
ce pt
good compromise between energy and conservation aspects. The aim of this work is to present a thermal, vegetal based insulating plaster, which has recently been developed within a research project, and to investigate its potential to reduce the heat flux exchanged through
Ac
the vertical envelope of historic buildings, by means of measurements carried out in both the laboratory and in the field, for a real case application. KEYWORDS thermal insulating plaster, building envelope, historic building, built heritage, energy refurbishment, retrofitting. 1. INTRODUCTION The refurbishment of existing buildings is a crucial point for the achievement of the energy and climate objectives of the European Union (EU) for 2020 and 2050. The energy performance of existing buildings is still very poor, and the construction sector is responsible, on average, for 35% of the energy consumption in Europe and in Italy [1]. The problem is made, even more complex in Italy, by the
Page 1 of 24
remarked presence of historic buildings, which constitute 20% of the existing building stock (2 out of 10 buildings were built before 1919) [2]. Passing from energy related aspects to the cultural ones, according to the Italian Constitution (art.9), historic buildings should be preserved and protected because they constitute a source of knowledge of the architectural history of the country. Consequently, the strategy concerning the protection of historic
ip t
buildings must be enhanced, and it could be more easily implemented if buildings continue to have a function and a role, as theorized by Annoni in 1946 [3]. Specific maintenance interventions, are therefore
cr
needed to refurbish the buildings from the energy point of view. Although historic buildings are usually
us
excluded from the obligation of adopting specific energy standards, energy related aspects should be faced and managed in order to exploit the building “usability” potential, so as to create acceptable indoor
an
environmental quality and energy efficiency conditions.
The energy refurbishment of this kind of building is a very complex matter that leads to a number of
M
question concerning conservation and valorisation of the building aspects and which require “one case at a time” approach [3], when deciding how and where to intervene on a building.
ed
A literature review has shown, that a qualitative and quantitative approach to the energy and sustainability of heritage buildings needs to be applied [4]. Furthermore, the lack of a methodology, technologies and
ce pt
knowledge on historic building retrofitting has been observed. Till now, only a few experimental and modelling activity researches have been conducted on this topic [5,6]. One study has recently presented a methodology, based on MCDM analysis (multiple-criteria decision-making), to select the best solution for
Ac
the internal insulation of a brick wall in a historic building [5]. Thanks to the relatively easy installation and reversibility, thermal insulating plaster seems to represent a very interesting solution, as it is able to offer a good compromise between energy and conservation aspects for those buildings where it can be applied (i.e. no frescoed walls). The first results of a research project, aimed at developing new kinds of plaster and insulation materials with low embodied energy, are presented. In this work, the analysis has focused on a new thermal, vegetal based plaster, developed specifically for internal insulation. In particular, the study here presented deals with its applicability to the internal side of an existing historical building envelope under refurbishment, and assesses the impact on the thermal flux reduction.
Page 2 of 24
The thermal insulating plaster has been tested in the laboratory to assess its thermal properties and in a real historic building, to investigate its potential to reduce the heat flux exchanged through the vertical envelope on which it has been applied. 2. THERMAL INSULATING PLASTER Plaster has been used for thousands of years as constructive element in buildings, especially in Europe. The
ip t
versatility of this material allows it to be both used internally and externally, with the possibility of applying rendering or plastering mortar to different substrates, constructions and compositions. Thermal insulating
cr
plaster represents one of the possible solutions that can be adopted to face energy related problems in
us
existing and historic buildings. The workability of thermal plaster is very similar to that of traditional plaster, as it can be used on non-aligned, out of square, or even on curved supports. Thermal insulating plaster is in
an
fact flexible and can be suitable for any architectural or design solution. Moreover, thermal insulating plaster is characterised by a high water vapour diffusion coefficient, with a water vapour resistance factor (µ value)
M
of between 5 and 15. For this reason, the application of this technology to existing walls is possible for envelopes affected by capillary rising damp, a problem which is very often present in historic buildings.
ed
Thermal insulating plaster has been studied not only to be a finishing or a protection layer of the walls, but also to improve their thermal resistance. These special kinds of plaster are characterised by thermal
ce pt
conductivity values that are more than ten times lower than traditional plaster (standard lime plaster 0.7 W/(mK)) and they are divided into two categories: plaster with natural binders (natural hydraulic lime) and plaster with cement or artificial binders. These types of plaster are usually pre-mixed and ready to use and
Ac
are made with Light Weight Aggregates (LWA), such as cork, clay, perlite, pearls of expanded polystyrene, expanded glass, etc. LWA are able to significantly improve the thermal and acoustical insulation performances of the component. Additionally, the weight of the component is noticeably reduced, compared to traditional ones [7].
New kinds of thermal insulating plaster are still being studied to reduce their thickness and to improve their thermal conductivity. Research is moving towards new aggregates, that is, innovative or natural materials. High-tech solutions, such as aerogel or phase change material (PCM) based plaster, are also being investigated.
Page 3 of 24
In this paper, the results related to traditional and advanced materials for thermal plaster are presented, with particular focus on the thermal properties of a vegetal based plaster. Vegetal aggregate materials, derived from corncobs, were added to a natural Wasselonne hydraulic lime and expanded silica (perlite), and the resulting plaster was tested through a laboratory analysis and in field measurements. The particle size distribution of the ingredients was studied in the laboratory to obtain the best combination from the physical,
ip t
mechanical and thermal points of view. Wasselonne lime is a Natural Hydraulic Lime (NHL 2, according to the EN 459-1:2010 standard [8]) that has been extracted since 1932 in the Alsace region, France, and it
cr
constitutes a significant percentage of the final product. The natural aggregate in these prototypes was 43%
us
(33% corncobs and 10% of dried expanded silica) and it played a double role: firstly, it contributed to an improvement in the insulation of the plaster by exploiting a waste material (i.e. the corncobs) and, secondly,
an
the mechanical properties of the plaster were improved and the risk of cracking was hence reduced. Furthermore, the natural binder gave a high water vapour diffusion coefficient to the plaster (that is, higher
wall using a plastering machine (Figs. 1a and 1b).
M
than cement binders). Application tests were carried out by spraying the thermal insulating plaster onto a test
ed
The results have showed that this technology is capable of supporting greater thicknesses of thermal insulating plaster (above 10 cm) than traditional insulating plaster. The same result could only be achieved
ce pt
using a traditional plaster through the repeated application of thin plaster layers onto its support with the consequent risk of cracking. The sample that passed the first mechanical test and presented the best performance was named VGT_04, and the results related to this sample are hereafter presented. The results
Ac
concerning long - term decay and the marcescence and oxidation processes are not yet available, but these important aspects are currently under investigation. Furthermore, on the basis of the ISO 14040:2006 standard [9], a life cycle analysis is also being conducted. 3. THE MEASUREMENTS 3.1 Laboratory measurement methodology Laboratory measurements have been performed to assess the equivalent thermal conductivity of the thermal plaster samples (10 cm thickness and 60x60 cm size, as shown in Figure 2a). A set of experimental measurements was carried out with heat flow meter apparatus, in accordance with the EN 12667:2001 international standard [10]. The apparatus, a Lasercomp FOX600, consists of a single sample, heat flow
Page 4 of 24
meter with a guarded ring equipped with two plates containing heat flow meters placed above and below the sample (Fig. 2b). Specifications details of the equipment are given in Table 1. The instrument was designed and set up in accordance with the ASTMC518, 1991 [11] standard and it was calibrated with “1450b NIST SRM” calibration reference samples and an EPS sample (expanded polystyrene). All the samples were previously tested and certified by NIST. In order to avoid any additional
ip t
surface resistances, due to the sample discontinuity, all the specimens were sandwiched between two rubber 3 mm sheets with a thermal conductivity of 0.073 W/(mK) at 10 °C. The uncertainty of the measured thermal
cr
conductivities were determined for each measurement in accordance with ENV 13005:1999 [12]. The
us
resulting uncertainty values were within ±2%, according to EN 12667:2001 [10] (annex B), including the additional uncertainty caused by subtracting the resistance of the rubber sheets.
an
Laboratory measurements were performed on two different samples (A and B) of the same thermal plaster (VGT_04 with natural Wasselonne hydraulic lime and vegetal aggregate materials). Before the tests, both
M
specimens were dried to constant mass in a ventilated oven for 48 h at 60°C to determine their mass. The relative loss in mass was calculated comparing the mass of the samples before and after the drying cycle. The
ed
tests were carried out at three different mean temperatures: 10, 25 and 40 °C, respectively, with a temperature difference of 20 °C, to minimize temperature - difference measurement errors.
ce pt
As is known the measurement principle is to create a constant temperature difference between the upper plate and the lower plate, and to measure the specific heat flux and surface temperatures in steady state conditions. The equivalent thermal conductivity [W/ (mK)] is then calculated using Equation 1, where s is
Ac
the sample thickness [m], q is the specific heat flux [W/m2] and ∆ts is the temperature difference between the two faces of the plate [°C].
eq (s q ) / t s [W/m°C] (1)
3.2. Laboratory measurement results The sample specifications are shown in Table 2. Samples A and B differ mainly as far as the density is concerned: sample A presents a higher density than sample B for both humid and dried samples. The thermal conductivity of the two different samples is reported in Table 3. In Figure 3, which shows the equivalent thermal conductivity vs. average temperature of the plates, it is possible to observe the influence of the water content on the thermal conductivity. Page 5 of 24
Both samples demonstrate quasi-linear behaviour: the difference between the dry and the humid samples is between 8% and 17% for sample A, and between 3% and 4% for sample B, depending on the set-point temperatures. The divergence between samples A and B was due to their different water contents. The experimental results show that vegetal aggregates have a great potential to reduce the thermal conductivity of plaster, compared to traditional cement thermal plaster with lime. From an analysis of the
ip t
results merges that, the thermal conductivity of the thermal insulating plaster (VGT_04) is 0.08 – 0.13 W/(mK) range while the reference sample is the 0.25-0.27 W/(mK) range. This means that samples A and B
cr
are 2.5 and 3 times more insulating than the reference sample. It should be emphasized that the results
us
achieved with these natural aggregates are in line with the literature values [13] obtained for different aggregates (i.e EPS, cork).
an
3.3. In field measurements: the case study
In order to investigate the performance of the analysed technology on an actual building, a set of
M
measurements was performed in a real application on the building envelope of a historic building under refurbishment in Turin, the ex Albergo di Virtù, 1580 (Fig.4). This historic building, which has a
ed
monumental value for the city of Turin, will become to a top category hotel, reinstating its original function. The vertical opaque envelope of the building presents a 500 mm thick and heterogeneous (brick and stone)
ce pt
wall. Thanks to the involvement of the contractor in the project, it was possible during the refurbishment to use two identical rooms with the same South - East orientation as test rooms. A 60 mm layer of thermal insulating plaster, made up of Wasselonne natural hydraulic lime and vegetal aggregate materials (VGT_04),
Ac
was applied to the wall of a room facing the external environment (Fig.5a); in the other room, the same external reference wall was left without any internal finishing (Fig. 5b). The air temperature was controlled in both rooms through electric heaters, with a temperature set point of 23°C. The thermo-physical behaviour and the energy performance of the vertical envelope was assessed by means of the continuous measurements of the heat flux, surface temperature and air temperature (according to ISO 9869-1:2014) [14]. The position of the probes was decided after an infrared image campaign of the investigated walls through a NEC Thermo Tracer (TH9100 MV/WV). In this way, the sensors were positioned in homogenous and representative areas of the wall (avoiding thermal bridges and discontinuity of the material). Heat flux meters, which had previously been tested in the laboratory, were placed on the
Page 6 of 24
internal surface of both walls. The internal and external surface temperatures and the indoor and outdoor air temperatures were measured by means of thermocouples (TT-types, previously calibrated in the laboratory). The instruments were connected to two data loggers placed in each test room, which retrieved data every 15 minutes. Hourly values were then calculated off-line for the data elaboration. The thermal performance of the wall with VGT_04 was established, on one hand, through an assessment of
ip t
the thermal transmittance and, on the other hand, through the calculation of the daily transmitted energy. The equivalent thermal transmittance was evaluated through the progressive average methodology, where the
cr
average values, of the specific heat flux (in W/m2) and the temperature differences between internal and
(Q / A) n (t s ) n
[W/m2°C] (2)
an
U*
us
external air, were used instead of the instantaneous values (ISO 9869 1994) [14], according to equation (2).
The total daily transmitted energy e24 (in Wh/m2) is defined as the energy transferred through the façade on a
M
daily basis. The convention used during the measurements was that a negative value of heat flux meant heat losses and a positive one meant heat gains. The total daily energy (equation 3) was then obtained from the
indoor surface of the façade.
ed
integral over the 24 h (from 00 am to 00 pm of the following day) of the surface heat flux exchanged on the
24:00
ce pt
e24
(q )dt [Wh/m ] (3) 2
00:00
3.4. Infield measurement results
Ac
The first step of the infield measurement was an infrared image campaign. It was necessary to verify the homogeneity of the walls in order to evaluate where to position the sensors. The infrared and visible images of the two tested walls are presented in Figure 6. The surface temperature is slightly lower in the lower part of the plastered wall, on the floor and below the window, due to thermal bridges and discontinuity of the material. The surface temperature of the reference wall is affected to a great extent by the finishing discontinuity. A central position, where the node with the lateral partition wall did not influence the surface temperatures, was chosen for the heat flux meter. The daily energy of a seven days campaign, characterised by a rather high temperature difference between the indoor and the outdoor environment, is plotted in Figure 7. Boundary conditions, during the selected
Page 7 of 24
days, were similar in the two test rooms. The average air temperature in the room with the thermal plaster (VGT_04) in the selected days was between 22.6 and 23.6 °C, while an average daily indoor air temperature of between 22.5 and 22.8 °C was measured in the reference room. A minimum average daily outdoor air temperature of 11.7 and a maximum value of 17.7 °C were measured in the considered days. In Figure 7, it is possible to notice that the energy losses through the reference wall are always higher than
ip t
those through the wall with the thermal plaster. The measured heat flux values are negative for each day. Since the outdoor air temperature was always lower than the indoor air temperature, the daily energy that
cr
crossed the reference wall was between 20% (day 3) and 41% (day 7) higher than the daily energy through
us
the VGT_04 wall. As the boundary condition and the wall structure were the same, it is possible to state that the difference monitored between the two test rooms was due to the presence of the thermal plaster layer.
an
In order to have a more complete picture of the energy performance of the tested wall, a new measurement campaign was carried out in a more representative period, in order to collect enough data to assess the
M
thermal conductance/transmittance of the wall with the average method. The data collected in this first campaign, which was performed in a cold April (very cold nights but also sunny days) shows highly
transmittance in a proper way.
ed
dynamic behaviour of the wall, and it was therefore not possible to define the stationary equivalent thermal
ce pt
The equivalent thermal transmittance of the plastered wall was 0.56 W/(m2K), as shown in Figure 8, which means a thermal transmittance of the bare wall of about 0.8 W/(m2K), calculated assuming the thermal resistance of the thermal plaster as resulting from the ratio of the measured value of the thermal conductivity
Ac
to the real applied thickness. Unfortunately, it was not possible to measure the bare wall in the other test room since it was under refurbishment during the second measurement period. The comparison between the two values confirm that 6 cm of VGT_04 thermal plaster can reduce heat loss by about 30%. 4. CONCLUSIONS
In this paper, thermal insulating plaster has been investigated as a possible option for historic building refurbishment. A new thermal insulating plaster was obtained adding to the natural hydraulic lime of Wasselonne, vegetal aggregate materials deriving from the waste of the corn production, which lend higher mechanical properties to the plaster and allows higher layer thicknesses.
Page 8 of 24
Results concerning laboratory measurement and the monitoring campaign in a real application on the building envelope of a historic building located in Turin are discussed. The low thermal conductivity of the new material, which is 2.5/3 times lower than conventional plaster, has led to a significant reduction in the energy that crosses the wall (about 20% - 40%). Other analyses are ongoing with the aim of further diminishing this value. However, its good hygrothermal
ip t
behaviour and its very low embodied energy already make it a real competitive and marketable solution for the retrofitting of existing buildings. Future work is necessary in order to evaluate the decay of the
cr
technology in long-term application.
Wh/m2 W/m°C W/m°C
q Q
W/m2
specific heat flux heat flux
M
m thickness °C surface temperature difference 2 W/m °C equivalent thermal transmittance
ACKNOWLEDGEMENTS
ed
s Δts U*
W
daily energy equivalent thermal conductivity thermal conductivity
an
e24 λeq λ
us
NOMENCLATURE
ce pt
The research was developed in the framework of the POLIGHT project “SI2 – Sistemi isolanti innovativi”, funded by the Regione Piemonte. The project was developed in co-operation with DAD_Politecnico di Torino, VIMARK s.r.l., AGRINDUSTRIA s.n.c., CLUSTER s.r.l., ARTI E MESTIERI and ATC Torino-
Ac
Agenzia Territoriale per la casa della provincia di Torino. REFERENCES
[1] Strategia Energetica Nazionale: per un’energia più competitiva e sostenibile, marzo 2013, approved by DM 8 march 2013. [2] ISTAT 2013. Rapporto Bes. Il benessere equo e sostenibile in Italia, capitolo 09, Il paesaggio e patrimonio culturale, march 2013. [3] A. Annoni, Scienza ed arte del restauro architettonico. Idee ed esempi, Edizioni Artistiche Framar, Milano, (1946), p. 14.
Page 9 of 24
[4] K. Fabbri, Energy incidence of historic building: Leaving no stone unturned, Journal of Cultural Heritage, 14s (2013) e25–e27. [5] J. Zagorskas, E. K. Zavadskas, Z. Turskis, M. Burinskiene, A. Blumberga, D. Blumbergaba, Thermal insulation alternatives of historic brick buildings in Baltic Sea Region, Energy and Buildings, 78 (2014) 3542.
ip t
[6] F. Ascione, F. De Rossi, G.P. Vanoli, Energy retrofit of historical buildings: theoretical and experimental investigations for the modelling of reliable performance scenarios. Energy and buildings, 43 (2011) 1925-
cr
1936.
us
[7] L. M. Silva, R. A. Ribeiro, J. A. Labrincha, V. M. Ferreira,. Role of lightweight fillers on the properties of a mixed-binder mortar. Cement & Concrete Composites, 32 (2010) 19-24.
an
[8] EN 459-1. 2010 - Building lime. Part 1: Definitions, specifications and conformity criteria. [9] ISO 14040. 2006 - Environmental management - Life cycle assessment - Principles and framework.
M
[10] EN 12667. 2001 - Thermal performance of building materials and products - Determination of thermal resistance by means of guarded hot plate and heat flow meter methods - Products of high and medium
ed
thermal resistance. [11] ASTM C518. 1991. Test Method for Steady-State Heat Flux Measurements and Thermal Transmission
ce pt
Properties by Means of the Heat Flow Meter Apparatus. [12] ENV 13005. 1999. Guide to the expression of uncertainty in measurement. [13] F. Favoino, M. Perino, V. Serra, Improving thermal performance of plasters by means of recycled and
Ac
phase change materials. Proceedings, in: Healthy Buildings 2012, Brisbane (AU), 8 - 12 July 2012, 1-2. [14] ISO 9869. 1994. Thermal insulation - Building elements - In-situ measurement of thermal resistance and thermal transmittance.
Page 10 of 24
Table(s) with Caption(s)
Table 1, Experimental apparatus (hot plate) specifications ~ 0.01 - 0.2 ~1 ~ 0.5 ~ ± 0.03 ~ ± 0.025 ~ 610 x 610 254 x 254 ~ 203
W/(mK) % % °C mm mm mm mm
Table 2, Samples of VGT_04 specification Sample size
[kg/m3] 507 496 402 400
[mm] 600x600 600x600 300x300 300x300
Sample thickness [mm] 100 100 50 50
us
Density
M
Sample “A” Sample“A dry” Sample “B” Sample“B dry”
Time of drying [h] 0 48 0 48
an
Name
cr
ip t
Thermal conductivity range Accuracy Reproducibility Temperature control stability Thickness measurement precision Maximum sample size Actual measuring area Maximum sample thickness
Sample B λeq λeq.dry [W/(mK)] [W/(mK)] 0.092 0.088 0.089 0.086 0.086 0.083
ce pt
Sample A λeq λeq.dry [W/(mK)] [W/(mK)] 0.126 0.105 0.115 0.100 0.107 0.098
Δλ [%] ±2% ±2% ±2%
Ac
taverage [°C] 40.00 25.00 10.00
ed
Table 3. Sample VGT_04 A and VGT_04 B thermal equivalent conductivity results for Δt=20°C
Page 11 of 24
List of Figure Captions
List of figure captions Figure 1. a) Evaluation of the possible thickness for thermal insulating plaster applications (left) b), Mechanical application of the thermal insulating plaster (right) Figure 2. a) Thermal plaster sample (left), b) Experimental apparatus: hot plate (right)
ip t
Figure 3. Experimental result: thermal conductivity vs average temperature of the plates for samples A and B of VGT 04, for both humid and dry conditions, and a reference cement thermal plaster
Figure 5. a) Tested wall with the thermal plaster, b) Reference tested wall
cr
Figure 4, Piazza Carlina Turin, ex Albergo di Virtù during the refurbishment
us
Figure 6. Infrared images: test room with the thermal insulating plaster VGT_04 (upper), and the bare wall of
an
the reference test room (lower)
Figure 7. Daily energy through the reference wall and the thermal insulating plaster wall
Ac
ce pt
ed
M
Figure 8. Equivalent thermal transmittance of the tested wall with thermal plaster VGT_04 (b)
Page 12 of 24
ed
pt
ce
Ac M
an
us
cr
i
1a
Page 13 of 24
ed
pt
ce
Ac M
an
us
cr
i
1b
Page 14 of 24
d
te
Ac ce p us
an
M
cr
ip t
2a
Page 15 of 24
d
te
Ac ce p us
an
M
cr
ip t
2b
Page 16 of 24
ed
pt
ce
Ac M
an
us
cr
i
3
Page 17 of 24
ed
pt
ce
Ac M
an
us
cr
i
4
Page 18 of 24
d
te
Ac ce p us
an
M
cr
ip t
5a
Page 19 of 24
ed
pt
ce
Ac M
an
us
cr
i
5b
Page 20 of 24
ed
pt
ce
Ac M
an
us
cr
i
6
Page 21 of 24
ed
pt
ce
Ac M
an
us
cr
i
7
Page 22 of 24
ed
pt
ce
Ac M
an
us
cr
i
8
Page 23 of 24
*Highlights (for review)
-
Thermal insulating plaster is a possible option for historic building refurbishment
-
A new thermal insulating plaster vegetal based is investigated in the laboratory and infield on a real historic building
-
Vegetal aggregate materials lend higher mechanical properties to the plaster and allows higher layer thicknesses
ip t
The low thermal conductivity of the new material led to a significant reduction in the energy that
ce pt
ed
M
an
us
cr
crosses the wall
Ac
-
Page 24 of 24