9 Green Building Materials: Steel & Concrete Alternatives for Construction

Once upon a time, we all lived in houses made out of sustainable building materials. While concrete may be strong enough to build a castle, it comes at a cost to our environment. 

But living in an eco-friendly home doesn’t have to be a fairytale. We’ve found nine natural building materials that you can use on your construction site without feeling guilty. 

We even found one interesting building material that is growing in your garden! Do you know which one?

1. Earth

When talking about concrete alternatives and other natural materials, I always like to start with earth. 

There is a misconception that houses made from earth are primitive. But the reality is you can have a fully decked-out home without using precast concrete slabs! Heck- you can even install the best low-flow toilet!

So let’s talk about some different ways you can build with earth.

a. Adobe Vs. Cob

Adobe is a mix of clay-rich soil, sand, and straw. It is shaped into a brick using a mold and then sun-dried (1).

Like concrete blocks, you can stack adobe bricks to construct sturdy walls.  

Making adobe bricks is pretty straightforward and economical — if your soil content is right. It’s helpful to have good sun for the drying and hardening process. But you can stockpile your brick, just making a few at a time until you are ready to build. 

About adobe and cob, people use the terms interchangeably, but they are different materials. 

Adobe is mixed wet, shaped into a brick, and dried. Cob is mixed wet and shaped into a house (or a stove or other structure). It is one piece of monolithic architecture — you could think of it as one giant adobe brick.

Most cob houses are round and resemble hobbit holes, ideal if you want to create concrete-like shapes naturally. But you can build a traditional home from cob too. You can still find delightful old cob cottages in the Southwest of England that are quite cozy and relatively square (3). 

b. Rammed Earth

Rammed earth is another interesting construction technique that uses earth. So, how does it work?

First, you’ll need to build a framework. Then, you’ll mix dry aggregates such as clay, sand, silt, gravel, and a small amount of cement. Once the mixture is ready, you’re going to pour it into the wooden forms. Modern rammed earth buildings often have rebar or bamboo in them to create sturdy walls. 

A ram will then repeatedly compress it. 

Traditionally, people use wooden poles. Nowadays, a mechanical ram is preferred since it’s faster and less labor-intensive (4). 

c. SuperAdobe

SuperAdobe, or Earth Bag as it is also called, involves filling long sandbags with earth. They are stacked up and held together with barbed wire (5). This technique allows for earthquake-resistant homes to be constructed quickly and affordably (6). 

2. Straw Bales

Straw bales houses were first constructed in Nebraska in the 1900s (7). They may seem straight out of the three little pigs story, but they provide excellent insulation (8). 

Other than the extra-thick walls, you would never know it’s made from conventional building materials. But those extra-thick walls are what make them such energy-efficient homes (8).

Straw bales can be either load-bearing or non-load-bearing. (9). A non-load bearing straw bale house will need lumber or metal pillars to support the roof. We’ll talk more about which green building materials are best for framing your home in a bit. 

Whether your bales are load-bearing or not, you stack the bales one on top of the other to build the wall. When your walls are complete, you apply a vapor barrier and then plaster. Plaster is an essential structural part of your walls, so make sure you give it the attention it deserves (10). 

3. Recycled Plastic

When it comes to eco-friendly building materials, recycled materials rank right up there. The easiest way to use recycled plastic is to make sure you look for post-consumer recycled plastics like old water bottles that would otherwise wind up in a landfill (11).

But you don’t necessarily need to buy something new to use recycled plastic in your home. 

Watch how you can make plastic construction beams. 

If you want to talk about truly alternative building materials, check out recycled plastic bottle bricks. In Guatemala, people recycle trash and plastic bottles and turn them into strong and lightweight bricks (12). They do this by taking all their non-organic waste, like plastic bags and chip wrappers, and filling a plastic bottle until it is rock hard.  

4. Recycled Metal

While you will never convince me the steel industry is eco-friendly (mass timber isn’t any better), sometimes we just have to use metal in our homes. But rather than using new steel beams in our homes, we can use recycled steel. 

Don’t worry. You can use steel over and over again without losing its quality (13). Recycling steel rather than creating it helps cut down on greenhouse gas emissions. It does this by minimizing carbon dioxide released during the industrial processes. 

5. Bamboo

Bamboo is another popular eco-friendly building material. It’s super sustainable as well! Guinness Book of World’s Records named bamboo as the fastest growing plant in the world! (14). Plus, you can harvest bamboo as young as four years old and use it as a construction material (15).

Not only does bamboo grow fast, but it is super strong when used correctly. In fact, bamboo is more robust than steel in tensile strength (16). 

One main concern about building with bamboo is pests – insects can eat untreated bamboo (17). Commercial products like bamboo floor tiles use chemicals to make them pest-resistant, but it is possible to treat bamboo naturally to keep the insects away (18).

6. FSC Wood/Salvage Wood

Did you know it takes about 44 mature trees to create a standard 2600 square foot home? (19) And, it will take between 35 and 70 years for a tree to be useful for lumber? (20) 

But don’t despair if you dream of natural materials like wood in your home. There is an eco-friendly way to source wood. Look for FSC wood or salvaged wood. 

If you are looking to use new lumber, the Forest Stewardship Council, or FSC for short, has a certification process, so you have an assurance that your lumber is coming from an ethically managed forest (21). 

Your other option is to use recycled wood, often referred to as salvaged or reclaimed wood. Salvaged wood can come from anywhere- demolition sites, dealers, online, and more (22). Plus, using reclaimed wood will bring a unique feel to your home that you just can’t buy in the store.  

7. Mycelium

As people are racing to find the newest and greatest green construction materials, mushrooms, or more precisely mycelium, are gaining a lot of attention.

Mycelium is the root-like structure of mushrooms. When dried, they turn into a super-strong, mold, water, and fire-resistant building material (23). The best thing about mycelium is that you can grow them into the shape you want, which is just what people are doing (24). 

People are growing this carbon-neutral material to create lightweight and strong bricks. While these are not as strong as traditional concrete, they are much lighter and more environmentally friendly (25).

8. Hempcrete

No, hempcrete isn’t a festival for pot-smoking hippies. It’s a concrete-like building material that uses fast-growing hemp and lime (again construction material- not fruit) to make lightweight bricks for insulation and infill in walls (25). 

Hempcrete isn’t as strong as concrete, so it’s not advisable for foundations or load-bearing walls (26). But its insulative qualities make it worth checking out for your green home.

9. Sheep’s Wool

We’ve mentioned insulation a few times now because it is crucial to your home’s energy efficiency. And the truth is most homes out there could use more insulation, especially if you’re considering affordable green prefab homes. But do you want to add more fiberglass batt insulation into your home? 

While we mentioned that hempcrete is a good insulator, another option with minimal environmental impact is sheep’s wool.

Available in batts or blown-in sheep’s wool has a similar or greater R-value to other insulators (26). 

The Bottomline

There are many sustainable construction materials that you can use as concrete alternatives. You can choose earth, bamboo, and more! By doing so, you can lower greenhouse gas emissions and help improve the health of our planet and, most importantly, your family. 

Even if you don’t want to live in a cob hobbit-hole, you can incorporate eco-friendly construction materials. It can be as simple as choosing recycled material, purchasing reclaimed wood, or adding insulation material like sheep’s wool instead of fiberglass.