Thermal Performance of Natural Insulation Materials for Energy Efficient Buildings

Wood waste as an alternative thermal insulation for buildings

The research presented in this paper proposes structures of timber frame exterior walls using reed straws as insulation materials. Having thicknesses of 175 mm and designed for exterior building walls, the proposed structures are composed of 12-mm-thick oriented strand board, 150-mm-thick insulation material with and without air layers, a vapour barrier foil and 12.5-mm-thick gypsum board for the interior face of the wall. The insulation materials used as reference for the proposed structures are polystyrene and rock wool. Reed straws used as insulation material for the tested wall structures formed insulation layers of 150 mm thickness in five configurations: 150-mm loose-fill reed straws without air layer and other four variants with loose-fill reed straws and 100-, 50-, 20- and 10-mm-thick air layers, respectively. The air layer was placed at the contact with gypsum board for all configurations. The reference structures (rock wool and polystyrene as insulation materials) followed three of the configurations set-up, namely 150-mm-thick insulation material (rock wool or polystyrene) only and insulation materials with air layers thicknesses of 100 and 50 mm, respectively. The eleven tested structures were subjected to thermal conductivity coefficient (λ) measurements. The tests were performed on HFM436 Lambda equipment. The structures were tested for an entire cycle of temperatures varying between − 10 and 30 °C and thus simulating summer and winter climate conditions. The thermal conductivity coefficient of the exterior walls filled with loose reed straws as insulation material was recorded between mean values of 0.076 and 0.077 W m−1 K−1, except the structure with an air layer of 100 mm, for which a value of 0.120 W m−1 K−1 was registered.

Investigation of usability of boron doped sheep wool as insulation material and comparison with existing insulation materials

Ecological impact & financial feasibility of Energy Recovery (EIFFER) Model for natural insulation material optimization

Wood Fiber vs Synthetic Thermal Insulation for Roofs Energy Retrofit: A Case Study in Turin, Italy

Many new insulation materials are being developed and thermally tested aiming at understanding and improving their insulation characteristics in order to improve the energy performance of new and existing buildings. Bio-sourced materials appear among the new insulation solutions presenting the advantage of being able to save energy on one hand and having a low environmental impact on the other. The wood fiber material is one of the most successful natural insulation materials being recently used in building constructions. It presents many advantages besides its insulation performance; due to its density, it stores moisture thereby improving the indoor air quality; it is also an excellent acoustic insulator because it has a natural tendency to absorb and reduce sounds. In order to evaluate its effectiveness in building applications, this study analyzes the hygrothermal modelling and performance of the wood fiber insulation in building applications by adopting two approaches: A numerical approach using a mathematical model that describes heat and mass transfer within the wood fiber material being considered as porous media. The hygrothermal characteristics of the wood fiber material are first determined experimentally for this purpose, namely the thermal conductivity, the heat capacity, and the isotherms of sorption and desorption. An experimental approach is carried out in controlled and uncontrolled ambiance conditions in order to validate the numerical model. A 50 cm × 50 cm wood fiber sample having an 8 cm thickness is tested for this purpose. A very high accordance is observed between the measured and modelled results for both the temperature and the relative humidity evolutions within the sample at x = 2 cm and x = 4 cm with a mean difference \( \overline{\Delta \mathrm{T}} \) of 0,21 °C at x = 4 cm and 1 °C at x = 2 cm. The maximum recorded differences for the relative humidity are: 5,5% and 4,5% at x = 2 cm and 4 cm respectively. The ability to predict the thermal and the hygric behavior of the wood fiber insulation will thus allow a better understanding of the efficiency of natural insulation materials.

Investigation of the thermal behavior of the natural insulation materials for low temperature regions

Noise is an unwanted sound in urban areas. Natural and or recycled acoustic absorbing or insulation materials are invented to reduce air and or impact sounds in buildings. Yet, they are not widely and commercially available. This review presented an overview of relevant studies on natural materials particularly on cotton and rubber using Scopus search engine and of the patents registered and granted using Espacenet and Google Patents search engines on noise reduction in buildings from the years 1996 to 2023. The 18% and 68% (out of 32 articles) relevant articles, respectively, were written on cotton and rubber and other recycled natural material e.g., consumed teabags, rubber crumb, indicating a clear vision for experimentation and modeling of natural materials e.g., to investigate their sound absorption coefficients at lower frequencies (below 250 Hz) for (recycled) cotton sound absorbing materials and for producing ultralight density with high sound absorption materials (0.56) using recycled rubber material. There were found 31 patents registered and granted, in total. Natural materials, namely, cotton, rubber, glass wool and rock wool were applied in 29% of patents registered and granted from 1996 to 2022. Yet, 93% of patents registered and granted lacked data on sound absorption index of materials they invented. LDA models estimated 29% of Espacenet and Google Patents patents registered and granted having an increased trend of patent innovations for example, in method, structure and building materials in the last decade.

A review of unconventional sustainable building insulation materials

In this study, the reduction of CO2 emissions caused by energy savings due to thermal insulation materials applied to the exterior of buildings was investigated. The study includes the evaluation of four different insulation materials including XPS, EPS, PUR and Rock Wool in terms of the reduction potential of CO2 emissions for all city centers in Turkey. Moreover, the optimum insulation thicknesses of the buildings that have both heating and cooling needs were determined for these insulation materials by means of Life Cycle Cost Analysis. The annual energy needs per unit area of the external walls of the buildings, which are insulated according to their optimum insulation thickness were determined and correspondingly the amount of fuel needed to meet this energy was calculated. In the study, CO2 emission values released from buildings to atmosphere were compared in terms of fuel amounts obtained from total energy demands during heating supplied from natural gas and cooling supplied from electricity of the residential buildings insulated with diverse insulation materials. Consequently, when CO2 reduction potentials of the buildings insulated with materials in the optimum insulation thickness are compared with those of the uninsulated buildings, insulation material providing highest potential in CO2 emission mitigation was to be found as Rock wool.

To reduce CO2 emissions and save grey energy, natural materials like wood and wooden materials are becoming more and more important. However, these products are particularly sensitive to moisture, as they can be attacked by mould or decay fungi. In contrast to mould growth, which typically is associated with visual impairment and health problems, the growth of decay fungi may result in structural defects which clearly must be excluded. Up to now it is mostly assumed that wooden materials are more sensitive to such attack than solid wood. Therefore, different wood fibre insulation materials were inoculated with decay fungi and exposed to different climates to determine the requirements for the decay process and to compare them with the requirements of decay by the same fungi of solid wood. The results prove that some natural fibre materials are equally or even more resistant to decay fungi than solid wood, while others are less. The resistant products can therefore be assessed like solid wood – for which already temperature dependent thresholds and in part also transient decay prediction models are available. Maybe even specific higher moisture levels can be acceptable. However, the results also suggest a differentiated view on natural fibre insulations, as they have a very different susceptibility to wood decay. Uniform and significantly lower limits than for solid wood are not justified.

This applied study focuses on evaluating the effectiveness of several thermal insulators on the thermal performance of buildings in the city of Riyadh in the central region of Saudi Arabia. Typical models equipped with different types of thermal insulators in their walls were used in this study. The experiment was conducted at the Research Station of the College of Architecture and Planning on King Saud University Campus in Riyadh. The study aims to know the effect of a number of modern artificial insulation materials commonly used in the insulation of buildings in the Kingdom as well as some natural materials available at construction sites on the thermal performance of buildings. The study used a number of thermal insulators manufactured and commonly used in the city of Riyadh, such as glass wool, perlite and polystyrene. A number of cheap natural materials well known in the traditional architecture of their good thermal properties and available on most construction sites or near them such as mud, sand and mixture of these two materials were also examined. The experiment was conducted in the winter season and the summer season of the same year, where readings were taken for the months of December and August to represent the two seasons respectively. Readings of indoor air temperatures were collected and analyzed and presented. The results of the study concluded that the use of a mixture of sand and mud is effective when used in the insulation of the external double walls. It was also revealed that the rest of the artificial and natural insulation materials used in the experiment were very close in their performance. The study concludes with some appropriate architectural recommendations for the possibility of using the mixture of soil and sand to achieve acceptable thermal insulation as well as economical benefits for buildings in the city of Riyadh and similar areas of the desert climates.

The demand for natural insulation materials is increasing with special attention to the use of such materials for exploiting renewable energy. Natural insulation materials tremendously influence the sustainability development and energy efficiency enhancement in the buildings. Natural fibers from animal’s origin absorb great amount of moisture on exposed to the environment which significantly affects the performance and thermal insulation properties. The thermal degradation of such material strongly influences the accidental burning characteristics, an important selection criteria for building materials. In the present study, three different kind of natural insulation materials namely sheep wool, goat wool and horse mane have been characterized in terms of moisture absorption, thermal degradation and morphology using thermogravimetric analysis (TGA), differential scanning calorimetry techniques, and scanning electron microscopy, respectively. In addition, antibacterial behavioral study has been also carried out for untreated raw wool and treated wool (copper nitrate). These properties are vital for a holistic evaluation of the insulation material. Moisture absorption results indicate that the sheep wool and goat wool absorb less moisture content as compared to horse mane. Unlike this horse mane shows great stability than goat wool and sheep wool in the temperature range not exceeding 470 °C. TGA data indicate 50% mass loss (T50%) at 306 °C, 322 °C and 318 °C for sheep wool, goat wool and horse mane, respectively. In addition the tests show that the content of fire retardant elements like nitrogen and sulphur is more in horse mane as compared to sheep wool and goat wool. The treated wool samples showed excellent antibacterial properties as compared to untreated wool samples.

Contemporary tendencies of sustainable and energy-efficient architecture imply an urgent reconsideration of society’s relationship to nature. Nowadays, building technology demands a responsible approach to construction that involves fostering of low-tech architecture, as an alternative to high-tech architecture. Those are current challenges that architects and the building technology face to improve the application of natural materials in architecture. The necessity for advancement and contemporary usage of building materials as wood, stone, soil, straw, natural insulation materials have also resulted in the increasingly present low-tech architecture. This research aims to delineate through several contemporary case studies how serious global problems related to the energy and environmental crisis are increasingly reflected in the intention towards the use of natural materials in the architectural design. These contemporary designs implement innovative solutions of natural materials in the case of building envelopes, construction details or structural elements. The comparative analytical method involves a critical reflection on the integration of natural materials between traditional vernacular application and its contemporary innovative solutions. These contemporary precedents represent diverse design approaches that reinforce the importance of environmental and ecologically responsible design. Current problems related to the energy and environmental crisis highly influence the underlying design concepts and final building design. The contemporary usage of natural materials as a building resource indicates the evolving advancement and re-evaluation of an ecologically responsible architecture. Whereas the contemporary ways of integrating natural materials carry universal values which originate from the principles of vernacular architecture.

Development and performance evaluation of natural thermal-insulation materials composed of renewable resources