Thermal Characterization of Textile Waste Materials for Reuse in the

Energy Refurbishing of Buildings

EUGENIA ROSSI di SCHIO, VINCENZO BALLERINI, PAOLO VALDISERRI

Department of Industrial Engineering DIN,

Alma Mater Studiorum – University of Bologna,

Viale Risorgimento 2, 40136 Bologna,

ITALY

Abstract: - The study’s findings suggest new applications for End-of-Life Household Materials (EoLHMs),

with a focus on new materials derived from textile wastes. The aim is twofold: explore innovative methods to

promote the circular economy by reusing EoLHMs in the building sector and refurbishing buildings with

particular attention to home-made panels, to favour disadvantaged contexts. Three different materials were

tested, and their thermal conductivity was measured according to the ISO 8301 standard. The thermal

conductivity as a function of the density was also investigated for a material derived from hemp. Comparisons

with other textile materials are presented as well. As a result, the thermal conductivity of the materials ranged

from 0.035 to 0.049 W/(m K), typical for insulating materials used in refurbishing applications.

Key-Words: - Reuse, thermal conductivity, thermal insulation, circular economy, energy efficiency, textiles.

Received: March 19, 2024. Revised: August 21, 2024. Accepted: September 13, 2024. Published: October 18, 2024.

1 Introduction

An important aspect is supporting sustainable

development, promoted by the United Nations

through one of its 17 goals, [1]. This includes

reducing inequalities, improving health and

education, and protecting the environment. Europe

faces the challenge of energy poverty, where many

people can't afford adequate heating, cooling, and

lighting, leading to disease, death, and social

isolation. Reusing waste materials, such as surgical

masks [2], or new materials, is particularly

beneficial as it allows people in disadvantaged

contexts to self-produce and install panels in their

homes. This not only improves indoor comfort but

also enhances human capital.

In the literature, thermal insulating materials

made from recycled waste are now widespread,

including those derived from textiles [3], [4], rubber

[5], cigarettes [6], agriculture [7], [8], [9], and

construction elements [10], [11]. By leveraging

local labor, EoLHMs can be transformed into

building components, promoting social inclusion.

The context of energy retrofitting of buildings is

of great interest because, as is well known, buildings

are responsible for a significant percentage of

energy consumption [12], especially in light of the

recent variability in energy costs, [13]. In this

framework, in the literature, attention has been paid

to green walls [14] and to their impact on energy

consumption and indoor comfort [15] and mainly to

the building envelope retrofit [16], [17], [18] as a

strategy to provide comfort coupled with energy

savings, without compromising functional needs.

In this framework, in the present work, we aim

to present the experimental thermal characterization

of new materials coming from textile wastes, from

the perspective of possible reuse as thermal

insulants.

2 Problem Formulation

The materials analyzed are produced from textile

waste. In this preliminary analysis, to calibrate

laboratory activities, we present data related to three

different samples, presented in Figure 1 and named

A, B, and C. Samples B and C are made of the same

material but with two different densities.

The A panel is made from mixed fibers recycled

from various types and colors of yarns. These fibers

are thermally bonded, a thermal cohesion process

that produces the material without adding any

chemical components. Moreover, this process

makes the material very stable over time and

resistant to moisture and infiltration. This material is

also easily workable and suitable for thermal and

acoustic insulation of walls, floors, and roofs.

The panels will be attached with mechanical

fasteners or gypsum-based adhesives on a brick

support. A notable feature of this product is its

complete recyclability during dismantling.

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DOI: 10.37394/232015.2024.20.46

Eugenia Rossi Di Schio,

Vincenzo Ballerini, Paolo Valdiserri

E-ISSN: 2224-3496

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(a)

(b)

(c)

Fig. 1: Materials A (a), B (b) and C (c)

The B and C panels are made from thermally

fixed hemp and kenaf fibers. This production

process gives these panels lasting thermal and

acoustic performance and makes them resistant to

the effects of moisture. They can be used for

external or internal insulation or with dry systems,

and their installation involves the use of mechanical

dowels or lime-based adhesives on brick support.

This material is also completely recyclable during

dismantling. Additionally, this material promotes

the breathing cycle, retaining excess moisture in the

cold months and releasing it in the warm months.

3 Experimental Measures

The measured density is reported in Table 1.

Table 1. Density of the samples

Test specimen

Density (𝒌𝒈 𝒎−𝟑)

31.3

33.7

64.9

Fig. 2: Thermal conductivity of the panels obtained

by experimental measurements. For each panel,

three different test repetitions were performed

Thermal conductivity tests were conducted at

the University of Bologna (Italy). After weighting

and conditioning, a heat flow meter, designed to

analyze materials with a thermal conductivity of less

than 5 W/(m·K), was used following the ISO 8301

standard, [19]. During the test, the sample was

placed between a hot and a cold plate, each

maintained at constant temperatures by two

thermostatic baths, with an insulating layer to

minimize lateral heat losses. Data acquisition was

carried out using a multimeter, a switch control unit,

and an ice point reference.

Each measure was repeated, and the results are

summarized in Figure 2. Figure 2 also delves into

the dependence of the thermal conductivity on

density: indeed, two different densities are

considered concerning the material constituting

sample B and sample C. Analogously to the findings

concerning face masks [2], also for this new

material higher density had lower thermal

conductivity.

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Eugenia Rossi Di Schio,

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To better understand and contextualize the

obtained data, we will now evaluate the thermal

conductivity of raw textile materials, using samples

from reuse reported in Figure 3. The analyses were

performed employing the same heat flow meter

located at the University of Bologna (Italy).

Fig. 3: Materials D (cotton crumped in ordered

arrangement), E (wool in disordered arrangement),

F (polyester in crumped in ordered arrangement),

and G (Jeans in ordered arrangement)

The materials are given by cotton (D); wool (E);

polyester (F) and Jeans (G), and their thermal

conductivity and density are reported in Figure 4.

This figure shows that thermal conductivity varies

with material type, with cotton exhibiting higher

conductivity than wool and polyester despite similar

densities. Cotton and denim, both cellulose-based,

differ in fiber density due to the manufacturing

process, affecting conductivity. This confirms that

density influences thermal conductivity, as

previously noted.

After having tested the materials layered in an

orderly manner, we decided to rearrange them in a

disordered manner and cut them into small bites.

Results are reported in Figure 5, showing that

the variation in arrangement within the sample

generally yields an improvement in the thermal

performance of the materials, except in the case of

wool. In this case, the fabrics already provide ample

air spaces: a disordered distribution likely increased

these spaces to the point of allowing the formation

of convection currents inside, as shown in Figure 5.

For cotton, polyester, and jeans, however, the

introduction of these air spaces improved thermal

performance, especially for the first of the three.

Fig. 4: Thermal conductivity and density of samples

made of cotton (D), wool (E), polyester (F), and

Jeans (G). Data refers to materials disposed in

ordered arrangement within the test specimen

Fig. 5: Effect of an ordered arrangement (O),

disordered rearrangement (D), and of 5 cm bite (5)

on the thermal conductivity of samples C, D, F, and

G. (For example, DO refers to the test specimen D

in ordered arrangement)

Figure 5 shows that the measured thermal

conductivity varies between 0.047 and 0.101

W/mK, typical values for fibrous materials objects,

[2]. However, thermal conductivity depends not

only on the material but also on the arrangement and

size of the elements. Different relationships were

observed among these three factors for the various

materials. For cotton, polyester, and jeans, thermal

conductivity decreased when the fabrics were

arranged in a disordered manner, while cutting the

fabrics improved conditions for wool and polyester.

Finally, a comparison with other reuse materials can

then be performed. The benchmark is reported in

Figure 6, where data from the literature are

employed, [2], [20]. The figure shows that the

lowest thermal conductivity values are reached for

face masks placed inside cardboard boxes and that

values of the same order of magnitude of the

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Eugenia Rossi Di Schio,

Vincenzo Ballerini, Paolo Valdiserri

E-ISSN: 2224-3496

480

Volume 20, 2024

materials measured in the present paper are reached.

Indeed, a comparison with insulating materials

typically employed in building refurbishing is

reported in Figure 7, showing that mainly high-

density material C displays very interesting features.

Fig. 6: Comparison of the thermal conductivity of

insulating panels made of reusable materials placed

inside cardboard boxes (CB) [2], [20], in various

configurations: for polyester and felt, a variable

amount of material (7 or 20 g) was considered based

on the position inside each egg box

Fig. 7: Comparison between the experimental

results obtained (best values) and the values of

typical commercial insulant. It is observed that the

“C” panel has a conductivity close to that of

commercial insulants

4 Conclusion

This study investigated innovative methods to

promote the circular economy by reusing End-of-

Life Healthcare Materials (EoLHMs) in the building

sector, focusing on panels built from textile wastes.

Three different materials were tested, and the

thermal conductivity was experimentally measured

according to the ISO 8301 standard.

The thermal conductivity of the tested materials

ranged from 0.035 to 0.049 W/(m K), typical for

insulating materials in refurbishing applications.

Concerning a material derived from hemp, the

dependence of the thermal conductivity on density

was deepened. Analogous to the findings

concerning face masks, higher density had lower

thermal conductivity for this new material.

Future analyses will focus on different materials, as

well as on the acoustic performances of those

materials.

Acknowledgement:

The authors are grateful to Mr. Matteo D’Orazi and

Mr. Dario Zanghirati for their cooperation in the

experimental activities.

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Eugenia Rossi Di Schio,

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E-ISSN: 2224-3496

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Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

The authors equally contributed to the present

research, at all stages from the formulation of the

problem to the final findings and solution.

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

We acknowledge financial support under the

National Recovery and Resilience Plan (NRRP),

Mission 4, Component 2, Investment 1.1, Call for

tender No. 104 published on 2.2.2022 by the Italian

Ministry of University and Research (MUR), funded

by the European Union – NextGenerationEU–

Project “Sustainable Thermal and Acoustic self-

made solutions for buildings refurbishment in

disadvantaged social contexts by Reusing poor

materials (STAR)” – CUP J53D23002280006 -

Grant Assignment Decree No. 961 adopted on June

30, 2023 by the Italian Ministry of Ministry of

University and Research (MUR).

Conflict of Interest

The authors have no conflicts of interest to declare.

Creative Commons Attribution License 4.0

(Attribution 4.0 International, CC BY 4.0)

This article is published under the terms of the

Creative Commons Attribution License 4.0

https://creativecommons.org/licenses/by/4.0/deed.en

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WSEAS TRANSACTIONS on ENVIRONMENT and DEVELOPMENT

DOI: 10.37394/232015.2024.20.46

Eugenia Rossi Di Schio,

Vincenzo Ballerini, Paolo Valdiserri

E-ISSN: 2224-3496

483

Volume 20, 2024