Natural Building Insulation

Cork

Cork is a high performance, natural, sustainable and vapour permeable insulation for use internally and externally. It is 100% recyclable and has very low embodied energy. Cork also has excellent acoustic qualities. Cork is an extremely clean insulation which does not emit any toxic fumes. It is resistant to damp and rot and is unattractive to mice and termites.

Cork originates from the bark of the cork oak tree which is common in Southern Europe and North Africa.

Cork insulation is made from natural cork which is removed from a tree about every 9 years after the cork tree has grown for about 25 to 30 years. The tree is not harmed in this process and does not need to be cut down. The cork bark grows back over time.

The processing of cork insulation is relatively low energy and does not require chemicals or artificial binders. The cork is cut from the tree and then left to rest for about a year. It is then boiled and left to dry out. It is then ground down into cork granules which are then pressed under high pressure and steam to make the boards. The cork creates a natural binder in this process which forms the board.

Cork insulation can be applied in many different forms: As insulation boards, as loose granules which may be suitable where access is restricted. It can also be mixed with a hydraulic lime binder to form a render/plaster that can be applied internally or externally.

Straw

Straw bale is an extremely sustainable option for insulation. It has low embodied carbon and is a waste product from a farming process.

Straw bale walls are extremely thick which can be a nice design feature however may make it not commercially viable when land space is limited.

Transporting the straw bale will probably be one of the biggest aspects of its embodied carbon so using local straw bale can be an extremely sustainable option for wall construction.

Straw bale is 100% biodegradable but can last over 100 years if properly maintained.

Sheep’s Wool

Sheep’s wool is a highly efficient natural thermal and acoustic insulation. It is a sustainable, user friendly and breathable insulation.

Sheep’s wool has a simple process from a sheep’s back to construction site. The sheep are first organised in relation to their colour for sorting purposes. The sheep are shaved and their wool is pressed into bales. The fibre thickness, length, colour and vegetable content are marked on the bales.

At the scouring plant the bales are opened and mixed to create a standard blend. The wool is then washed in warm water in a series of baths. Once fully washed, the sheep wool is then treated to protect it from moths and insects.

Once dried, the sheep’s wool is combed so that all the fibres are running in the same direction, these layers are then mechanically bonded to create standard rolls of insulation.

Hemp

Hemp is a fast growing, easy to cultivate plant that produces strong and woody fibres which can be used to create a hemp wool that can be used as a highly efficient and sustainable building insulation. It is resistant to mould and bacteria and only a little energy is used for its production into a building material.

At the end of its life, hemp insulation can be recycled or ground up for compost. Hemp is usually combined with other materials such as recycled polyester to create insulation products for the construction industry.

Hemp can also be combined with lime and sand to create products such as hempcrete which can act as non-load bearing walls. Hempcrete is not as efficient as hemp wool insulation in terms of thermal performance.

Cotton

Recycled denim can be used as a high performing, sustainable building insulation. Jeans are recycled by the public then shredded in a factory into small parts. Metal parts such as buttons and zips are removed in the factory by a machine. Once the fibres have been fully separated by the shredding process they are compressed and then receive fire protection treatment. Some companies use recycled polyester in the final mix of the insulation.

Wood

Wood is an extremely versatile material. Perhaps best known for is structural qualities and flooring in the construction industry, it can also be used as a highly sustainable building insulation.

Wood wool insulation is created by compressing and binding slender shavings of wood. A patent for this process was granted in 1908 in Austria and is still being developed today in the construction industry.

Wood fibre insulation is usually made from waste wood from sawmills. There is a wet and a dry process manufactures can use to create this efficient insulation. In the wet process, chipped and waste timber is ground into small pieces and boiled in water and other chemicals which help break the timber into fibres. In this process, sugars which can support fungus and mould are removed. This slurry is then placed onto a sieve and compressed to remove the water. It is then heated with steam to bond the fibres together.

In the dry process. Ground up timber fibres are bonded with the same glue that bonds MDF and OSB boards. The dry process uses less energy than the wet process, making it a carbon negative material and cheaper to produce.

Cellulose insulation has been used in buildings for hundreds of years. It is a low cost insulation usually made by hammer milling waste newspaper. This is then treated to give it improved fire resistant qualities. Loose cellulose can be blown into wall cavities in existing buildings, making it an ideal insulation for improving the thermal performance of existing buildings, potentially without losing internal or external space.

Stone

By spinning molten rock and minerals with steel slag we get a mineral wool product which is a fantastic insulator and has excellent fire retardant qualities. Mineral wool is an extremely popular building insulation product which has been around for many years. Slag wool was first made in 1840 in Wales by Edward Parry and the technology is still being used and developed to this day.

Limestone/ Sand/ Soda Ash (glass)

Limestone, sand and soda ash are some of the raw ingredients of glass. Glass can be heated at very high temperatures until it melts and then spun quickly to create fibres which is commonly known as glass wool insulation or glass mineral wool. Usually, recycled glass used in the production of glass mineral wool.

Foam glass is a rigid, lightweight, durable insulation material composed of millions of sealed glass cells. It boasts properties such as incombustibility, high compressive strength, water tightness, vapour tightness and long lasting thermal insulation performance. It is usually made of mostly recycled glass. Foam glass can also be used as a gravel under buildings.

Earth

Earth can be used as insulation in the construction industry. It goes without saying that it is an extremely sustainable material.

Cob is a common building material which consists of subsoil and is usually mixed with some fiberous organic material such as straw and sometimes lime. The mixture can be modified with sand or clay. Cob wall are very thick and also have good thermal mass qualities.

Rammed earth is a technique of constructing building elements using earth, chalk, lime or gravel. Sometimes cement is used in the mix but this drastically reduces the embodied carbon of the wall. The process involves compacting a damp mixture of subsoil with a mix of sand, gravel and clay (historically sometimes with animal blood) into a formwork which is usually made of wood or plywood. It is usually compacted to about 50% of its original volume. This gradually built up in batches or courses. Historically this was done manually with a ramming pole but more modern interpretations of the wall include using electric powered tampers. Once this process is complete, the formwork is then removed and a surface texture can be applied if wanted.

It is also worth mentioning that monolythic clay blocks(fired clay) that have a honeycomb like section or similar can be used in wall construction with potentially improved thermal qualities to standard block or brickwork.

Grass

Grass can be used to create a highly efficient, sustainable building insulation material. A relatively new technology has been developed by the Swiss company Gramitherm to utilise grass as a viable building insulation.

Mushrooms

Mycelium insulation is a mushroom based insulation that has huge potential in the construction industry. It has great qualities that make it sustainable and high performing. Companies such as Biohm are developing insulation building panels that are suitable for building construction.

Feathers

We already have coats filled with feathers to keep people warm in the winter. We also already have feather filled bed duvets that keep people warm at night. However, feathers haven’t been the insulation of choice for buildings.

In 2020 there were more than 33 billion chickens in the world. Millions of tons of feathers are generated each year by the global poultry industry. Companies such as Aeropowder are developing processes that would allow them to use feathers that would otherwise be discarded in these industries as an insulation material in a variety of industries including the construction industry.

Flax

Flax insulation is a highly sustainable, high performing and breathable insulation, with good thermal and acoustic qualities. Flax has been used for thousands of years as a textile fibre and now it is being used by companies such as Isolina in Finland as an insulation product for the construction industry.

Rice Husk

Rice husks are the a shell that protects rice in the growing season and is a by-product of the rice growing economy.

Rice husk can also be used as a building insulation in the form of blocks or loose. Italian company Rice House are developing some interesting solutions using rice husk insulation.