“Insulation made from organic and sustainable materials and innovative composites is integral to reducing the embodied carbon and operational emissions associated with the thermal insulation of buildings.”
Adjusting indoor thermal conditions through heating and cooling makes up about 40 per cent of total global energy consumption, underscoring the potential benefits from minor reductions in heat flow and energy use and the lowering of related emissions.
The recommended approach to mitigating environmental and wellbeing issues in insulating materials is to find substitutes using secondary, renewable, or recycled sources that comply with sustainability and ecological requirements.
Low-carbon buildings that utilise sustainable materials and energy retrofits collaborate with renewable energy systems to enhance energy performance. High-performance insulation is crucial for reducing overall energy consumption.
It is estimated that poorly insulated roofs are responsible for more than 35 per cent of heat loss that occurs in a building, and the walls, if also poorly insulated, contribute an additional 25 per cent of heat loss, making the building’s thermal performance less than half effective.
Commonly used insulation materials include organic foams such as expanded polystyrene and polyurethane foams, and inorganic fibrous materials including glass and mineral wool.
However, conventional organic foams are produced from fossil fuels, resulting in a high embodied carbon contribution. Meanwhile, mineral wool is energy-intensive to produce and has raised serious health concerns around the release of fibres from the wool.
Types of insulation materials that support sustainable building include natural fibres – such as straw, hemp, wool, or flax – which are completely compostable and far less polluting than conventional insulation.
Certain types of cane, being water repellent, can also be used in insulation, as well as in roof cladding and earth bricks.
Growing awareness of the environmental and potential health concerns associated with traditional insulation materials has sparked interest in and the development of organic composites, textile fibres, and cellulose fibres.
Some examples of materials used to create insulating fibres include sheep wool, linen and cellulose derived from paper.
Other innovative materials with properties such as low density and high insulating capacity include aerogels, which are extremely lightweight due to their numerous microscopic air-filled pores, and vacuum-insulated panels, which feature a microporous core that is evacuated, encapsulated, and sealed within a thin gas-tight envelope.
Some natural insulation materials popular among researchers are wood, hemp, kenaf, cotton, flax, and crop-based byproducts such as straw, cereal husks, and vegetable pith.”
In particular, hemp wool, wood fibre and vegetable pith are widely used in the construction of breathable walls due to their hygrothermal performance.
Hygrothermal performance is the measure of a bio-based insulation material’s ability to absorb, store, and release heat and moisture (vapour or liquid), as well as maintain movement of airflow within a building’s interior.
Another key measure of insulation materials is the R-value, or thermal resistance, with the material’s effectiveness a function of its R-value and specific heat.
The R-value is calculated by dividing the thickness of a material by its thermal conductivity. This represents the temperature difference occurring per unit of material thickness in increments of one inch.
Wall and roof insulation typically should have a cumulative R-value of at least 30 and closer to 60 for buildings in colder climates.
Materials with a higher R-value offer better resistance to heat flow and overall insulation performance. While increasing the thickness of the material can achieve higher R-values, it also raises costs and necessitates additional maintenance.
A study published last year highlighted the increasing use of agricultural waste as reinforcement in bio-based insulation composites. These green composites can be used for insulation, frames, roofs, and other exterior or interior applications.
Agricultural residues consist of lignocellulosic materials and are abundant, cost-effective, non-toxic, sustainable, and renewable. Many farming wastes and biomass possess unique properties that enhance their insulation and soundproofing capabilities.
Bio-based agricultural residues and wastes have also been used as a constituent in gypsum plaster, cement, and other construction materials.
Creating more refined composites is an area of enormous potential, with many research projects finding a multitude of applications across a wide range of waste products, byproducts, and other natural materials.
A recent example is an innovative material made from bio-polyesters filled with date pits, developed by researchers at the United Arab Emirates University. This material presents a promising alternative to conventional insulation options.
The researchers successfully developed a biodegradable poly(-hydroxybutyrate) (PHB) composite with thermal conductivity values ranging from 0.086 to 0.1 watts per metre Kelvin, making it highly effective for insulation purposes.
They also demonstrated that the date-filled PHB composites provided excellent thermal insulation and exhibited high compressive strength of up to 80 megapascals with 30 per cent filler content.
The composites further showed promising water absorption of less than 6 per cent and a tensile strength in the range of six to 14 megapascals.
Another innovative insulating composite developed several years ago by researchers from Flinders, Deakin, and Liverpool universities was produced using wool fibres, sulphur, and canola oil.
Flinders University’s Professor Justin Chalker, lead author and New Innovators winner in the 2020 Prime Minister’s Prizes for Science, said the composite was one of several exciting new composites and polysulphde polymers made from waste products being commercialised.
He said: “This study aimed to evaluate a composite made from sulphur, canola oil, and wool as thermal insulation – the material is prepared by hot pressing raw wool with a polymer made from sulphur and canola oil.
“The promising mechanical and insulation properties of this composite bode well for further exploration in energy-saving insulation in our built environment.”
