The top 5 most eco-friendly building materials for a house

When people imagine housing projects, they often envision bricks, concrete, and steel. But are these materials really the gold-standard of construction? 

There are many sustainable materials entering or reentering the limelight as useful and viable options for the construction of homes. 

With sustainable architecture becoming more popular year-on-year, these are the top five most eco-friendly building materials you could use to build an eco house.

1. Hempcrete

An organic material made from a mixture of hemp fibres, lime, and sometimes sand, hempcrete is both a versatile sustainable construction material, but also a material that is a carbon sink, or “carbon negative”. 

This means that during the process of growing the hemp, more CO2 is absorbed by the hemp than is released during production and construction on-site. Along with its carbon-negative benefit, hemp is regenerative and fast growing, taking just four to five months to grow to completion.

Its sustainability and eco-friendly qualities are abundant, but what about its usefulness in construction? Well the first thing to note is hempcrete’s super-lightweight quality, making it easy to transport and use in construction.

Along with being lightweight, hemp is fire-resistant, pest-resistant, and an extremely strong insulator. As a breathable material, it allows the slow passage of air and water vapour, helping to regulate temperatures in a property.

Although not quite strong or dense enough to be used for building foundations, hempcrete provides an excellent alternative to concrete for walls, roofs, and other areas of sustainable construction.

2. Sheep’s Wool

Known primarily as a clothing material, sheep’s wool is one of the leading contenders for the UK’s primary sustainable home insulator. The amazing insulative quality of wool is common knowledge to the public, with many other popular wool products such as socks and jumpers keeping us warm in today’s society. Just like hemp, wool is a highly breathable material, allowing both good insulation and effective temperature regulation. It is super easy to install, non-toxic and safe, reasonably easy to source, and 100% sustainable. A single sheep can produce 2 - 30 pounds of wool annually, and will constantly and quickly regrow their wool once sheared by farmers. For those looking to create an eco-friendly building or home, sheep’s wool seems like the obvious choice.

3. Cork

Already an established sustainable and eco-friendly material in the construction industry, the true applications of cork are only just being explored. Cork comes from the bark of a cork oak tree. It is a renewable resource and does not require the tree to be cut down when harvested.

Due to its thermal and sound-insulation properties, cork is a popular material for the use of insulation and sub-flooring. It is also water, flame, and rot resistant making it an attractive housing material.

Architects such as Matthew Barnett Howland have begun to explore the use of cork blocks as a material for walls and roofs, all via dry-joints. The use of dry-joints allows the cork blocks to be reclaimed after-life. 

No glues or mortar are required - a tongue and groove geometry allow the blocks to slot into each other, binding them together with zero plastics involved.  All this combined with its lightweight nature makes it an excellent material for sustainable homes - it is versatile and has a low carbon footprint. 

4. Bamboo

Used most commonly in countries such as India, China, and Malaysia, bamboo can be grown in every continent save Europe and Antarctica. Both extremely lightweight and very durable, bamboo boasts a high strength-to-weight ratio. These qualities immediately make it an ideal candidate for flooring and sustainable interior design.

Though it may seem unbelievable, bamboo actually has higher compressive strength than even wood, brick, and concrete, and a tensile strength that rivals steel. Because of this, bamboo is hailed as an excellent resource for industrial scaffolding, as well as being used in housing foundations and providing the structural framework for housing walls.

Slightly reducing its sustainability rating, bamboo has to be treated before construction use, as without treatment bamboo is not pest-resistant. Location of the build must also be considered - transporting bamboo from Malaysia to Europe would drastically increase the embodied carbon of the material. However, bamboo’s amazing regeneration rate is another bonus, taking just 3-5 years to fully regrow, with some species of bamboo sprouting 3ft in just 24hrs of growth.

Though certainly a more readily-available resource in Asia, bamboo’s lightweight nature makes it cheap and sustainable to transport in large quantities, and is a great candidate for sustainable housing construction.

5. Cob

Created by mixing subsoil, straw (or other fibrous organic material), water, and often lime, cob is one of the oldest building techniques in human history. Many of the UK’s oldest homes are made from cob and now many, mainly architects, are keen to see it return to the construction industry.

Cob is naturally fire, mould, and pest-resistant. When treated and maintained correctly, cob buildings can last thousands of years. Cob walls are often treated with a lime wash to protect it from the rain and prevent it from becoming damp. 

Cob is extremely energy efficient, meaning that cob houses often require very little heating. This is because cob acts as an effective thermal store. However, to ensure the cob's thermal store effect is strong enough, you typically need thicker walls, often around 600mm or 2-3ft!

With cob being made from a mixture of earth, water, and straw, the resources are abundant. This makes cob construction a great choice for sustainable housing projects. 

And those are the top 5 most eco-friendly building materials! Special mention goes to recycled and reclaimed materials such as wood and steel. Although steel is only really a sustainable resource when being recycled or reclaimed, it couldn’t make it onto the list.

With a shift in focus to sustainability and saving the environment inside the construction industry, new breakthroughs in sustainable materials and building techniques are coming every year, and we’re excited to see what comes next!