Benefits of Building a Cob House: Sustainability and Cost
Have you ever considered building a sustainable and cost-effective house from natural materials like clay, sand, and straw?
If so, a cob house is ideal for achieving your goal. However, before going that route, you should know the sustainable and cost-related benefits of building a cob house.
Sustainable building is crucial, especially now that the construction industry is responsible for 50 percent of climate change. Besides sustainability, you don’t want to break the bank to build a house. So, knowing whether building a cob house aligns with your sustainability and cost-effectiveness goals is important.
In the rest of this article, I’ll discuss the benefits of building a cob house in terms of sustainability and cost. From embodied energy and resource efficiency to financial savings, let’s explore the advantages of cob houses together!
Sustainable Benefits of Building a Cob House
Low Embodied Energy
Embodied energy incorporates the energy required to produce, manufacture, and transport a building material.
A sustainable material must exhibit low embodied energy to qualify as being eco-friendly.
Low embodied energy means the material needs less energy for production, transportation, and installation.
Cob is made from sand, clay, and silt. In most cases, these products are readily available on-site.
You only need to access the subsoil by digging about 24 to 36 inches (60.96 to 91.44 cm). This eliminates the need for transportation, which would have otherwise contributed to a high embodied energy.
Moreover, processing cob involves hand and feet-mixing, which doesn’t require much energy. The material is also installed into the courses manually.
The above facts explain why, unlike other building materials, cob has a low embodied energy of 0.065 MJ-eq/kg.
The table below compares cob’s embodied energy to other materials:
| Material | Cob | Brick | Limestone Brick | Cement | Soil Cement | Steel | Timber |
| Embodied Energy (MJ-eq/kg) | 0.065 | 3 | 0.85 | 4.6 | 0.85 | 24.4 | 8.5 |
| Embodied Carbon (kgC/kg) | 0.036 | 0.06 | – | 0.23 | 0.038 | 0.48 | 0.12 |
Table 1: Embodied energy and carbon per kg of cob compared to other building materials. Source: Research Gate
Resource Efficiency
Cob houses are also resource-efficient because cob requires fewer resources to produce than other materials like concrete blocks or bricks.
To put that into perspective, producing concrete blocks requires burning coal and high energy. Coal is a non-renewable resource that emits hazardous by-products such as carbon dioxide.
Cob does not require any of that. The three primary materials required to make cob are clay, sand, and straw.
Clay, which is abundant in many areas, functions as the binder for the cob. Sand provides stability to the structure, while straw gives it flexibility and strength.
As a result, cob presents an eco-friendlier alternative with fewer resources and energy consumption than conventional building materials.
Energy Efficiency
The cost of energy is at an all-time high. As such, we all want energy-efficient homes to reduce our utility bills.
Cob houses are energy-efficient, thanks to their thick walls with high thermal masses.
In construction, thermal mass entails the ability of a material to store and release heat energy based on temperature variations.
The material absorbs and stores heat energy in warm temperatures. When the temperature drops, it releases the stored heat, warming the indoor environment.
Due to their high thermal mass, the thick walls of cob houses absorb and store solar radiation during the day. They then release the heat energy at night when temperatures drop, helping keep the house warm.
Consequently, you don’t have to rely as much on central heating, a factor that helps reduce your energy bills.
Durability
Cob houses are amongst the most durable structures on earth. The oldest known cob house has existed for more than 10,000 years.
How does durability impact sustainability? You may wonder.
Well, durability helps reduce the environmental impacts of frequent construction and demolition.
By reducing the need for frequent renovation or reconstruction, cob houses help eliminate waste removal, debris disposal, and energy costs associated with material production.
Also, since cob houses lack mortar joints, they’re highly resistant to seismic activity. They’re also fire-resistant. As such, you don’t have to worry about frequent repairs or replacement, leading to less resource wastage.
Non-toxic and Healthy
You don’t have to worry about toxicity when it comes to cob houses.
Cob houses are built from natural materials, meaning there’s no off-gassing of harsh chemicals, which means indoor air quality is better.
Additionally, since cob walls are porous and breathable, they help regulate indoor humidity levels by absorbing excessive moisture. Consequently, you don’t have to worry about mold, mildew growth, and associated health issues like allergies.
Moreover, naturally occurring materials also tend to have antimicrobial properties that inhibit bacterial and fungal growth. Thus, you can rest assured that your cob house is a healthy living environment for all occupants.
Low Carbon Footprint
Carbon footprint refers to the cumulative greenhouse gas (GHG) emanating directly or indirectly from an activity, a product, or an individual.
Cob houses have a reduced carbon footprint because they require fewer resources to build and maintain than other building materials.
Unlike concrete, you don’t need to burn fossil fuels to produce cob. Additionally, cob houses don’t require frequent repairs, leading to fewer GHG emissions from material production and transportation.
Also, since cob is not a manufactured material, it releases no toxins into the environment throughout its lifetime.
Overall, a head-to-head carbon footprint comparison between cob and conventional building materials will show that cob has a significantly lower carbon footprint.
Community Building
Sustainability encompasses the environmental, economic and social well-being of communities.
Building a cob house involves more than just you; it’s a community effort.
In most cases, the local community members join in to help with the construction process. This helps reduce labor costs while creating a sense of camaraderie and unity within the community.
Therefore, besides protecting the environment, cob houses help promote social sustainability.
Cost Benefits of Building a Cob House
Lower Construction Costs
Material costs typically account for 70% of the total construction cost of a house, depending on the material. Labor usually accounts for only 30 percent of construction costs.
Knowing this, reducing the cost of materials is the best way to lower your construction costs.
Cob houses are constructed from resource-abundant and inexpensive materials – clay, sand, and straw. In most cases, these materials are freely available on-site, lowering the construction costs considerably.
A simple comparison between cob and concrete reveals that while the former costs between $5 and $200 per square foot, the latter costs between $110 and $250 per square foot.
Since labor is the primary driving force behind the cost of cob houses, you can reduce the cost immensely by going the DIY route.
However, it’s worth mentioning that building a cob house is labor-intensive. Therefore, you’ll need sufficient elbow grease for a DIY project.
Lower Maintenance Costs
Cob is a durable material that’s highly resistant to pests and fire.
Moreover, due to its porous nature, cob acts as an indoor humidity regulator that prevents moisture accumulation.
Keeping your house free of moisture accumulation helps prevent water damage. This is why it’s important to finish your cob walls using a breathable lime render, not a non-breathable cement-based render or paint. Using breathable materials prevents moisture build-up and avoids the risk of water damage.
If you use the correct finishes, cob houses require less frequent repairs and maintenance, saving you money in the long run.
Low Energy Bills
As already discussed, cob has a high thermal mass and high heat capacity.
Materials with high heat capacity absorb and store a significant amount of solar energy during the day. As the temperatures drop, these materials release the stored energy into the environment, warming the surroundings and keeping living areas warm.
The high heat capacity of cob houses helps decrease the number of times the HVAC system has to kick in, resulting in lower energy bills.
The above explanation is the reason cob houses reduce the annual thermal load by 20 to 50 percent compared to conventional homes.
Furthermore, cob houses can be almost entirely self-sustaining when supplemented by solar panels or other renewable energy sources.
Final Thoughts
There you have it; the sustainable and cost-related benefits of building a cob house.
Cob houses are not only extremely sustainable but also cost-effective.
Compared to conventional homes, cob houses require fewer resources for construction and maintenance.
Moreover, we mustn’t underestimate this venture’s community building aspect – cob house construction helps unite a community, promoting social sustainability.
Before leaving, check out this comparison between bamboo and concrete for building for more sustainable building inspiration.
