Choosing a sustainable insulation material reduces energy use and environmental impacts. But there are many different insulation materials available, each with its own unique environmental impacts.
Foam plastic insulation such as XPS, EPS, and spray polyurethane foam is made from petrochemicals like ethylene and benzene derived from fossil fuels. They also require fossil fuel energy to mine, manufacture, and transport (see embodied energy).
Raw Materials
Insulation materials are comprised of many different materials, both organic and inorganic. Some organic insulators use natural components, such as fur, feathers, wood and sheep’s wool to slow the transfer of thermal energy. Other insulators use polymer based materials that rely on trapped air to slow the transfer of heat.
Inorganic insulators are made of minerals, such as sand, rock wool, vermiculite and perlite. These materials are dimensionally stable and can be supplied as mats, boards or pipes. They have a high hygroscopicity, which helps to retain moisture and restricts thermal transmission [1].
Glass wool, stone wool and expanded polystyrene (EPS) are manufactured by melting raw ingredients such as rock, glass sand, quartz sand or diabase and flinging the hot molten material out of a spinning machine. This process produces loose fibres that can be blown into building cavities, such as wall constructions. Mineral fibres are non-rotting, provide good fire resistance and have low toxicity.
Cellulose insulation is an eco-friendly insulator that can be made from recycled paper products, primarily newsprint. It packs tightly into a building cavity and manufacturers add a small amount of mineral borate to the product in order to ensure fire resistance, insect protection and reduce corrosion. It has an R-value of about 3.1 to 3.7. It is also being investigated as an effective and economical way to minimize the damage caused by fire in buildings.
Production Environment
The production of insulation materials is highly energy intensive. The embodied energy intensity of EPS, for example, is about 4.4 times that of steel (Source: Inventory of Carbon and Energy). This high embodied energy should be considered in the selection of insulation. Insulation manufacturers strive to reduce the energy used in the production process as well as reduce the use of fossil fuels.
For example, fiberglass batts are made using recycled glass, which reduces waste and the need for new materials. Mineral wool insulations such as rock and slag wool contain up to 30% recycled blast furnace slag, which cuts down on the amount of raw material used. Cellulose insulation is made of paper products, primarily newsprint. It also contains a small percentage of mineral borate. The borate provides fire and insect resistance.
Some cellulose insulations may lose their performance when exposed to moisture and must be protected against moisture through careful design of wall, floor and roof systems. Wood based insulations such as hemlock fiber, sawdust, spruce or redwood bark, hemp or flax fiber and wood fiber are hygroscopic and absorb moisture, reducing their thermal properties. This problem can be overcome through the use of treated cellulose, or with a moisture barrier.
The case study insulation materials of meadow grass, seaweed and reed and recycled jute are harvested and produced in Germany. Meadow grass is grown in the outskirts of Germany, while the seaweed and reed are harvested along the coastline of the Mediterranean Sea.
Recycling
Insulation is typically made from recycled materials. According to the 2020 REI Report, this reduces waste and energy consumption as well as reducing greenhouse gas emissions. Foam boards, for example, can be reused for other purposes or melted and reformed into a new product. Cellulose insulation is one of the most environmentally friendly types of home insulation and is made up of up to 80% recycled material.
This insulation can be installed in a variety of ways. It can be blown into place using special equipment, or poured in. It can also be cut into sheets or fitted between wood-frame studs, joists and rafters. This type of insulation can be used in open existing wall cavities or in insulated attic floors.
Foam insulation can also be sprayed into the walls, attic or crawl space of a new or existing home in its liquid state. It expands to fill the entire cavity and can be a good choice for hard-to-reach areas of the house.
Another form of foam insulation is injected into the walls of a house in a process called sprayed-in-place foam (SIB). This can be done in addition to or instead of traditional wood framing and has the added benefit of making the house more structurally sound. SIPs consist of a core of foam insulation covered with sheathing like oriented strand board (OSB) or other structural facing material.
Landfill
The most basic insulation materials reduce the use of energy in buildings, which lowers demand on utilities that rely on fossil fuels for power. However, some insulation types have a bigger impact on the environment during their lifetime than others. The key factor is the type of material used. Some, such as styrofoam and fiberglass, require the manufacture of plastics that can damage the earth, while others, such as cellulose and mineral wool, are made from recycled materials. Upgrading to these materials can significantly reduce a building’s environmental footprint.
Insulation materials are classified by their thermal conductivity, which is how well they transfer heat. Materials that have a low conductivity are better insulators. Mineral wool, which consists of rock and recycled glass, is relatively low in conductivity. Plastic insulation, such as expanded polystyrene (EPS) and extruded polystyrene (XPS), have small pockets or cavities that maximize air-trapping, but their structure requires petrochemical manufacturing byproducts.
Cellulose, which is the most common form of cellulose insulation, is composed of about 80% post-consumer recycled newspaper. The rest of the material is typically fire retardant chemicals and, in some products, acrylic binders. Other manufacturers produce cellulose insulation that does not require HCFCs, but their new products are not yet available on the market. One manufacturer, Resin Technology Company, is developing closed-cell and open-cell water-blown polyurethane insulation that do not use HCFCs.