Acta Polytechnica CTU Proceedings https://doi.org/10.14311/APP.2022.38.0203 Acta Polytechnica CTU Proceedings 38:203–209, 2022 © 2022 The Author(s). Licensed under a CC-BY 4.0 licence Published by the Czech Technical University in Prague CLOSING THE LOOP OF TEXTILE: CIRCULAR BUILDING RENOVATION WITH NOVEL RECYCLED INSULATIONS FROM WASTED CLOTHES Andrea Augello, Olga Beatrice Carcassi, Francesco Pittau∗, Laura Elisabetta Malighetti, Enrico De Angelis Politecnico di Milano, ABC Department, via Giuseppe Ponzio 31, 20133 Milano, Italy ∗ corresponding author: francesco.pittau@polimi.it Abstract. The implementation of new energy policies and standards for NZEB is expected to lead to a significant reduction of GHG emissions from building use in Europe in the next decades. On the other side, the growing pressure on insulation materials risks to significantly contribute to the exhaustion of the remaining carbon budget due to the high carbon intensity of conventional insulation for material processing. Consequently, storing carbon in construction products and promoting circular economies able to generate up-cycling processes from industrial or post-consumption waste are the key strategies to promote an effective transition toward a carbon-neutral society. Fashion & clothing is one of the manufacturing sectors which mostly contributes to waste generation and fossil GHG emission. This paper presents the main outcomes achieved from RECYdress project, which focuses on the valorisation of wasted textile collected by municipal districts to develop novel thermal insulations for building applications. Three alternative conceptual manufacturing processes were defined at lab scale based on different treatment of textile fibres, with produced specimens tested for thermal characterization. Finally, the LCA results of an ETICS application for façade renovation were compared considering as functional unit 1 m2 of façade with similar thermal resistance. Keywords: Textile wastes, circular economy, life cycle assessment, sustainability, thermal conductivity, transient plane source method. 1. Introduction To limit the high environmental impacts caused by the construction sector, the European Commission has promoted strategies and directives aimed at improv- ing the energy efficiency of existing buildings, largely inefficient from an energy point of view. The Euro- pean Green Deal constitutes one of the main issued strategies, which aims at the elimination of green- house gas production in Europe by 2050, through a gradual transition that will involve various sectors (transport, industry, agriculture, energy, etc.). Other instruments, such as the Renovation Wave, instead foresee an increase in the annual building renovation rate, currently between 0.4 and 1.2 %, over the next ten years, thus decarbonizing about 35 million build- ings. To promote the circularity of the economy and reduce the environmental impacts associated with building materials, numerous authors have studied the possibility of integrating wastes of different nature within construction products. Among these, textile waste has been shown to have potential as thermal in- sulators, thanks to thermal conductivities comparable to traditional insulating materials; therefore, the use of these materials within the construction sector could constitute a possible solution to the problem of recy- cling textile waste, which ends up mainly in landfills (57 %) or incinerated (25 %) at the end of their life. Furthermore, the problem of textile waste in Europe is expected to increase in the coming years due to the re- strictions imposed by the Waste Framework Directive, which imposes the mandatory separate collection of textile waste in all Member States by 2025, preventing landfill, incineration, or export of textile wastes to non-European countries. This paper summarizes the main results achieved from the RECYdress project, aimed at evaluating the development of thermal in- sulations based on recycled textile wastes. Different types of samples were analyzed, evaluating both their thermal and environmental properties, investigating the effect of parameters such as density, treatment, binder, and composition of the insulating material. 1.1. Textile-based insulation materials: a short literature review The thermal properties of textile wastes of differ- ent compositions have been studied by many au- thors in the last years. Dieckmann et al. [1] tested the thermal properties of insulation panels based on waste chicken feathers mixed with bicomponent fibers: the lowest value of thermal conductivity measured, equal to 0.033 W/mK, was comparable with conven- tional insulation materials. Similar results were ob- tained by Mrajji et al. [2], who investigated the ther- mal properties of six nonwovens based on different amounts of chicken feathers, cotton, and wool pro- duced with the needling technique: values between 0.0313 and 0.04465 W/mK were measured. The ther- 203 https://doi.org/10.14311/APP.2022.38.0203 https://creativecommons.org/licenses/by/4.0/ https://www.cvut.cz/en A. Augello, O. B. Carcassi, F. Pittau et al. Acta Polytechnica CTU Proceedings Figure 1. Thermal conductivity of textile wastes from literature. mal properties of polyester fabrics were investigated by Jordeva [3], analyzing different types of polyester shredded and inserted in casings made of polypropy- lene: their measured thermal conductivity values ranged from 0.052 to 0.0603 W/mK. Good thermal per- formances of polyester-based materials were obtained by Drochytka et al. [4], who tested five samples based on polyester fibers mixed with synthetic bicomponent fibers produced with the airlay technology: values between 0.04319 and 0.05598 W/mK were measured. The same airlay technology was adopted by Zach et al. [5], manufacturing and testing five insulation materials based on flax, cotton, and polyester. The measured thermal conductivities ranged from 0.036 to 0.0443 W/mK, depending on density and composition. The use of recycled wool as thermal insulation was studied by Rubino et al. [6] on four samples based on Merino wool waste bound with chitosan: thermal conductivity values ranging from 0.049 to 0.06 W/mK were measured. These samples were later compared by Rubino et al. [7] with other specimens based on merino wool bound with Arabic gum: chitosan and Arabic gum samples showed similar thermal conductivity val- ues. A few years later, Rubino et al. [8] analyzed five samples with different densities based on merino wool bonded with copolyester/polyester bicomponent fibers: lower values of thermal conductivity were obtained, going from 0.044 to 0.057 W/mK. Eventually, Rubino et al. [9] studied the combination of the previously investigated merino wool/Arabic gum samples with organic phase change materials. The measured ther- mal conductivities (between 0.053 and 0.085 W/mK) increased as function of the temperature and amount of PCMs, due to the increased connections among fibers and the reduction of the pore volume. The thermal performances of five samples based on wool and polyester were studied by Patnaik et al. [10]: the average values ranged from 0.032 to 0.035 W/mK, con- firming that it is possible to manufacture insulation materials with a similar thermal conductivity as that of 100 % waste wool fibers. The thermal behavior of wool and acrylic fibers was investigated by Wazna (El) et al. [11], producing four nonwovens based on acrylic and sheep wool wastes with the needling technique, characterized by low val- ues of thermal conductivity (0.0339–0.0355 W/mK). Another acrylic nonwoven fabric was investigated by Gounni et al. [12], confirming its capability to sig- nificantly reduce the heat flux (λ = 0.038 W/mK). Hadded et al. [13] investigated the effect of the me- chanical treatment on the thermal properties by con- sidering two textile samples obtained through the same process but at different stages: both materials presented low density and high porosity, with simi- lar thermal conductivities (0.033 and 0.039 W/mK). Hegyi et al. [14] investigated 13 samples made of differ- ent amount of recycled plastics, denim, or sheep wool mixed with bicomponent fibers; thermal conductivities between 0.032 and 0.053 W/mK were measured. The results obtained by the previously mentioned authors are reported in Figure 1. 204 vol. 38/2022 Closing the loop of textile: Circular building renovation . . . Figure 2. Tested textile samples. Dimensions: 10 cm3. 2. Materials and methods 2.1. Tested materials As shown in Figure 2, two different sizes of fibres were selected for thermal characterization: (i) staple textile fibres, and (ii) fabric strips with two alternative options to bind the layers: needle punched and vinyl adhesive. In total, twelve types of wasted textile samples were prepared for testing, distinguished between: (i) loose fibres (Denim_1, Denim_2, Cotton_1, Polyester_1, Polyester_2), (ii) thermal treatment (Cotton/BICO), and (iii) cut-out strips (Wool_1, Wool_2, Cotton_2, Cot- ton_3, Synthetic_1, Synthetic_2). The effect of composition, density, treatment under- gone by the materials, or binder on thermal conduc- tivity values was investigated. All textile fibres used in the test campaign were provided by Vesti Solidale Società Cooperativa Sociale, an NGO operating in Northern Italy with a business core on collecting and sorting wasted clothes. 2.2. Test methodology 2.2.1. Thermal characterization: Transient Plane Source method The measurements of the materials’ thermal conduc- tivity were carried out through the Transient Plane Source method, BS EN ISO 22007-2:2015, which is based on the use of a disk, called Hot Disk, which produces a thermal impulse on the material under examination and measures its change of thermal resis- tance; the model adopted by the software then allows to derive the thermal properties such as conductivity, diffusivity, specific heat, etc. For the loose textile wastes, the test methodology involves the use of some small wooden boxes (cube with a side equal to 10 cm) inside which the loose material to be tested is inserted; a hole located about halfway up the side allows the insertion of the disk in the middle of the sample; the dimensions of the boxes were chosen con- sidering the need of guaranteeing an adequate sample thickness to avoid any edge effects that could alter the results. For the composite materials, the disk was simply inserted between two equal samples with a thickness of about 5 cm each. At least six measurements were performed on each sample, to take into account the variability of the results; therefore, the reported thermal conductivities are intended as averages of six or more values. Be- sides, the uncertainties connected to the measurement method were evaluated by calculating the average standard deviations. 2.2.2. Life cycle assessment for carbon footprint calculation The Life Cycle Assessment is a methodology used to es- timate the environmental burdens associated with the entire life cycle of a product, process, or service, from raw material acquisition through production, use, end- of-life treatment (recycling or final disposal). The re- quirements and guidelines for carbon footprint of prod- ucts are defined in the standard ISO 14067:2018. This methodology is used to evaluate the carbon footprint of the textile-based insulation materials, which will be compared with those of traditional ones, to highlight benefits or disadvantages. Two functional units were adopted: 1 kg of insulation material and 1 m2 of panels with a thermal resistance of 2.22 m2K/W. The chosen system boundaries from “cradle to gate” include the phases between the textile wastes collection to the fi- nal product manufacturing. Among the tested textile samples, only the environmental impacts of cotton waste (Cotton_1) were assessed, combining the loose material with different amounts of bicomponent fiber (5 % or 25 % in weight). The analysis was performed on SimaPro using the Ecoinvent 3.8 database as the main source of data by considering the Italian energy mix for electricity driven processes. Other relevant data about energy consumption of machinery used for the manufacturing process were collected onsite from a Italian company operating in the textile industry. 205 A. Augello, O. B. Carcassi, F. Pittau et al. Acta Polytechnica CTU Proceedings Figure 3. Thermal conductivity of the tested loose (left) and composite (right) materials. 3. Results 3.1. Thermal characterization The tested samples were stored in the laboratory under a controlled environment before starting the measurements. The moisture content of some tex- tile samples was evaluated using a moisture analyzer (PCE-MA100), which measured an average moisture content of 8–9 %. The thermal conductivity values measured on the tested samples are reported in the following scatter plot (Figure 3), having the materials’ density as x-axis; the error bars represent the calculated thermal conduc- tivity’s uncertainties. All the loose textile materials showed low values of thermal conductivity, almost always lower than 0.06 W/mK, which makes them suitable as insulating materials; on the contrary, the Cotton/BICO sample is the only tested composite material that could be applied as insulation material. All the tested parameters, i.e. density, treatment, binder, and composition have a not negligible effect on the samples’ thermal properties. The thermal con- ductivity increases with the increasing density for four of the five tested loose materials: only the sample “Denim_1” has an opposite trend, i.e. a decreased thermal conductivity, going from 30 to 50 kg/m3. The treatment undergone by the materials, investigated by comparing the two types of polyester, seems to have a not negligible effect too: we registered a decrease of 16 % (in average) of the thermal conductivity for Polyester_2 on both the tested densities. For what concerns the effects of the binder on the thermal per- formances, the needled samples do not have excellent thermal performances: Wool_1 and Synthetic_1 have the best results, with conductivity values lower than 0.075 W/mK; on the contrary, Cotton_2 has a ther- mal conductivity value completely outside the range of the insulating materials (λ = 0.137 W/mK). In the case of adding glue to the samples, there is a further sharp decrement in thermal conductivity: for the Cot- ton_3 sample, an average value of 0.218 W/mK is measured (+ 59 % compared to the needled Cotton_2 sample), i.e. an unsuitable conductivity for an insulat- ing material; furthermore, measurement uncertainties are much greater than those calculated for the other tested materials. These problems are probably at- tributable to the nature of the chosen binder and to the large amount of water contained in it, which keeps the sample to be tested partially moist even for sev- eral weeks and which therefore could have had a not negligible effect on the thermal conductivity measure- ment. For these reasons it was not possible to evaluate the performance of the other two composite materials (Synthetic_2 and Wool_2) as they were excessively wet and with results not consistent with what was ex- pected as they were probably influenced by the initial materials conditions. This problem could represent the big disadvantage of the recycled textile wastes, since for many building applications it is necessary to guarantee a minimum water-repellent behaviour. 3.2. Carbon footprint assessment 3.2.1. Production processes The functional unit chosen to calculate the global warming potential due to the production process of the two textile wastes (Cotton/BICO 95/5 and Cot- ton/BICO 75/25) is equal to 1 kg of insulation ma- terial. The production process was divided into the following sub-processes: (1.) Collection and shredding. It includes: (a) Transport of textile wastes to the collection site located in Cinisello Balsamo (average distance of 15 km) (b) Production of low-density polyethylene for packaging (volume of 0.25 m3) (c) Transport of textiles to the production site located in Recanati (distance of 460 km) (d) Electricity consumption for textile shredding of 515 kWh (e) Water consumption of 160 l/h (f) Lubricant consumption of 10–20 l/h (g) Flame retardant consumption of 30–40 l/h (h) Allocation of the production of machinery used in this sub-process 206 vol. 38/2022 Closing the loop of textile: Circular building renovation . . . Figure 4. GWP, in kg CO2eq per 1 kg of insulation, of the two textile alternatives. Material λ [W/mK] Thickness [mm] Density [kg/m3] RT [m2K/W] Cotton/BICO 95/5 0.045 100 50 2.22 Cotton/BICO 75/25 0.045 100 50 2.22 EPS 0.035 78 20 2.23 Rockwool 0.035 78 60 2.23 Glasswool 0.032 71 50 2.22 Woodfibre 0.040 89 50 2.22 Table 1. Properties of the analysed insulation materials. (2.) Production of textile-based insulation. It in- cludes: (a) Production of bicomponent fibers in South Ko- rea (b) Transport of bicomponent fibers by ship to the Port of Genoa (distance of 18 000 km) (c) Transport of bicomponent fibers by trucks to the production site located in Recanati (d) Electricity consumption for textile thermopress- ing of 293 kWh (e) Methane consumption of 35 m3/h (f) Allocation of the production of machinery used in this sub-process (g) Production of packaging materials The global warming potential of the two insulations is represented in Figure 4, expressed as kg CO2eq/kg and as percentages respectively. The sample composed of 25 %m of bicomponent fibres presents the highest GWP-value, thus impacting 2.5 times more than the other sample made with 5 % of bicomponent fibres. This difference is mainly caused by the higher amount of bicomponent fibres and thus by their impacting production process, which represents 79 % of the total GWP of the 75/25 sample. 3.2.2. Comparison with traditional insulation materials After calculating the impact associated with the pro- duction process, a comparison with traditional insula- tion materials is performed (Table 1). The thermal resistance is adopted as functional unit, taking into ac- count the differences in terms of thermal performances: 1 m2 of panels with a thermal resistance of around 2.2 m2K/W. Furthermore, the benefits of the recycled and natural insulation materials are highlighted, cal- culating the amount of CO2 stocked by each kg of dry material obtained multiplying the carbon content and finally by converting carbon into CO2, through the mass equivalent coefficient 3.67. As already discussed in the previous paragraph, a higher amount of bicomponent fibres negatively af- fects the carbon footprint of textile-based materials. The quantity of stocked CO2 is affected by the per- centage of bicomponent fibres too, growing with their decreasing content: thanks to its low amount of bi- component fibres, the sample Cotton/BICO 95/5 is characterized by a negative net GWP value. 4. Discussion The methodology adopted for the thermal charac- terization of the insulation materials presents some criticalities and uncertainties related to the test pa- rameters adopted (time, voltage, hypothesis, etc.) and to the measurement method itself. It is known that the thermal conductivity measured by the Transient Plane Source method could be overestimated by about 10 % with respect to real values, as demonstrated by Colinart et al. [15]. Therefore, a comparison with other measurement methodologies (e.g., heat flowme- ter, guarded hot plate etc.) could help for the valida- 207 A. Augello, O. B. Carcassi, F. Pittau et al. Acta Polytechnica CTU Proceedings Figure 5. Carbon footprint (GWP) and CO2 stored in 1 m2 of textile and conventional insulation materials with a RT = 2.2 m2K/W. tion of the reported results. For what concerns the carbon footprint assessment, as shown in the following Figure 5, results are largely sensitive to the share of BICO used to bind the fi- bres though a thermal treatment. Nowadays, the EU demand of bicomponent polyester fibres (BICO) is almost fully covered by South Korea. The long dis- tant transportation and the high-carbon intensity for Country-specific energy generation largely affects the GWP of the final product. Investigation of possible alternative fibres, resulting from pet recycling process, should be investigated in order to define alternative low-carbon solutions for manufacturing the insulation panels. 5. Conclusions This article summarizes the main results obtained in the “RECYdress project”, which aimed at investigat- ing the properties of textile-based insulations, propos- ing alternative ways to recycle a material whose end of life is mainly constituted by landfill or incineration. The main findings of this research were: • textile wastes could be applied as insulation materi- als thanks to their low thermal conductivity values • as verified by many authors, the thermal conductiv- ity increases with the increasing material’s density • the treatment undergone by the textile wastes af- fects their thermal performance • the chosen binder, i.e. glue, negatively affects the materials’ thermal conductivity, due to the high amount of water contained • the GWP value of textile-based materials is mainly affected by the amount of bicomponent fibers and their production process; besides, the Cotton/BICO 95/5 sample is characterized by a negative net GWP value, thanks to its low amount of bicomponent fibers. Furthermore, future investigations could involve the measurement of the thermal properties of the tested materials with other methodologies, comparing and validating the obtained results. Besides, an additional analysis could concern the analysis of other types of textile materials, trying to improve both their thermal and environmental performances. Acknowledgements This work was part of the RECYdress project, funded by Duferco Engineering S.p.A. Particularly, authors wish to thank MEng. Emilio Castelli and MEng. Ezio Palmisani for their constant support during the research activities. Authors also acknowledge PhD Adriana Angelotti, PhD Alessandro Dama and PhD Andrea Alongi for their sup- port during the thermal characterization of the samples. References [1] E. Dieckmann, R. Onsiong, B. Nagy, et al. Valorization of waste feathers in the production of new thermal insulation materials. Waste and Biomass Valorization 12(2):1119–1131, 2021. https://doi.org/10.1007/s12649-020-01007-3 208 https://doi.org/10.1007/s12649-020-01007-3 vol. 38/2022 Closing the loop of textile: Circular building renovation . . . [2] O. Mrajji, M. E. Wazna, Y. Boussoualem, et al. 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Trans Tech Publications Ltd, 2022. https: //doi.org/10.4028/www.scientific.net/CTA.1.287 209 https://doi.org/10.1177/1528083719869393 https://hrcak.srce.hr/file/210294 https://doi.org/10.1016/j.proeng.2017.04.549 https://doi.org/10.1002/jctb.4940 https://doi.org/10.18280/ti-ijes.632-423 https://doi.org/10.3390/ma12234020 https://doi.org/10.1016/j.jclepro.2020.123905 https://doi.org/10.3390/app11031262 https://doi.org/10.1016/j.enbuild.2015.01.056 https://doi.org/10.1016/j.jobe.2017.06.008 https://doi.org/10.1115/1.4038786 https://doi.org/10.1016/j.jobe.2015.10.007 https://ijcs.ro/public/IJCS-21-16_Hegyi.pdf https://doi.org/10.4028/www.scientific.net/CTA.1.287 https://doi.org/10.4028/www.scientific.net/CTA.1.287 Acta Polytechnica CTU Proceedings 38:203–209, 2022 1 Introduction 1.1 Textile-based insulation materials: a short literature review 2 Materials and methods 2.1 Tested materials 2.2 Test methodology 2.2.1 Thermal characterization: Transient Plane Source method 2.2.2 Life cycle assessment for carbon footprint calculation 3 Results 3.1 Thermal characterization 3.2 Carbon footprint assessment 3.2.1 Production processes 3.2.2 Comparison with traditional insulation materials 4 Discussion 5 Conclusions Acknowledgements References