When comparing Compressed Stabilized Earth Block (CSEB) walls and Cob walls, it’s essential to understand the construction process, thermal performance, breathability, and overall durability of both. Here’s a detailed technical comparison between the two types of walls, explaining which one is better for keeping the interior warm in winters and cool in summers, and which wall performs better in terms of breathability.

CSEB Walls- CSEB blocks are manufactured using a mixture of soil (sand, silt, and clay) along with stabilizers like cement or lime. The soil is compressed under high mechanical pressure using a machine to form dense and stable blocks. These blocks are then cured for strength and assembled using mortar to form walls.

Example – A common recipe for CSEB involves 70% sand and 30% clay, mixed with 5-10% cement as a stabilizer. The mix is pressed into blocks with a hydraulic press at around 4 MPa (megapascals), creating durable and uniform bricks.

Cob Walls- Cob is a traditional building method where clay, sand, water, and straw are mixed and shaped by hand or foot into thick, monolithic walls. This mixture is applied in layers directly onto the building structure, without forming blocks. The walls are thick and load-bearing, relying on natural drying to harden.

Example- In cob construction, a mix of approximately 60% sand, 20% clay, and 20% straw may be used. This mixture is applied in 20 cm layers, with each layer left to dry before adding the next.

CSEB Walls- These blocks are dense due to compression, offering decent thermal mass but less insulation compared to cob. While CSEB walls absorb and release heat slowly, the thinner wall size (typically 20-30 cm) offers limited thermal resistance.

-Example- A 30 cm thick CSEB wall may have a U-value of around 1.5-2.0 W/m²K, meaning it conducts more heat and is not as insulating as cob.

Cob Walls – Cob walls are naturally much thicker, often around 50-60 cm, which significantly improves their thermal performance. Cob acts as an excellent thermal insulator because the material is less dense, allowing it to trap air within its structure. This means cob houses stay cooler in summer and warmer in winter.

Example- A 50 cm thick cob wall might have a U-value of around 0.5-0.8 W/m²K, which is much lower than CSEB, indicating better thermal insulation and reduced heat transfer.

CSEB Walls- While CSEB walls can breathe to some extent, their breathability is often reduced due to the use of stabilisers like cement. Cement blocks the natural movement of moisture, which can affect the indoor air quality and comfort.

Example- A CSEB wall stabilized with 10% cement will allow less air and moisture to pass through than a wall made with pure soil, potentially leading to trapped moisture inside the wall.

Cob Walls- Cob walls are highly breathable because of their natural composition and the absence of synthetic stabilizers. The straw in cob also helps with moisture regulation, allowing the walls to naturally absorb and release moisture from the air, creating a healthier indoor environment.

Example- Cob walls act like a sponge, absorbing humidity when indoor air is moist and releasing it when the air is dry, maintaining a balanced humidity level indoors.

CSEB Walls- Due to their high compression and the addition of stabilizers like cement or lime, CSEB walls are highly durable and can withstand adverse weather conditions. They are particularly resistant to erosion and have a long lifespan when properly maintained.

Example- A well-constructed CSEB wall can last over 100 years with minimal maintenance, as the blocks are designed to resist both compression and water penetration.

Cob Walls- Cob walls, while strong, are more susceptible to weather damage, particularly from water erosion. Cob requires additional protection from rain, such as wide roof overhangs and a good foundation. However, when properly maintained, cob walls can also last for centuries.

Example- Cob houses in England, some over 500 years old, are still standing, although they require regular maintenance, such as reapplying protective renders.

CSEB Walls- Although CSEB is more sustainable than fired bricks or concrete blocks, the use of cement or lime stabilizers does have an environmental impact. However, it still uses much less energy than conventional building materials.

Cob Walls- Cob is one of the most sustainable building methods, as it uses completely natural and local materials, and requires minimal energy during construction. It also has a low embodied carbon footprint, making it an eco-friendly option.

Thermal Comfort- Cob walls provide superior thermal comfort because of their thicker construction and better insulation properties. They naturally regulate temperature, making homes warm in winter and cool in summer.

Breathability Cob walls outperform CSEB in terms of breathability, creating a healthier indoor environment.

Durability -CSEB walls are more durable and require less maintenance, especially in regions with heavy rainfall or harsh weather conditions.

If you’re seeking a more durable, low-maintenance wall, CSEB may be the better choice. However, for a natural, eco-friendly home with excellent thermal performance and breathability, cob walls are ideal.