MAIL: Compressed Earth

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Compressed stabilized earth blocks (CSEBs)
Compressed stabilized earth blocks (CSEBs)

I was a little surprised by the omission of compressed stabilized earth blocks (CSEBs) from the discussion of high-performance wall systems in HP154. Human beings have been building with earth for millennia, but the modern popularity of CSEBs is largely attributable to Raul Ramirez, of the Inter-American Housing Center (CINVA) in Bogota, Colombia. Ramirez patented a clever, manually operated brick press in 1952.

CSEBs are very similar to adobe and rammed earth, but have several advantages, especially for the prospective owner-builder. As the name implies, CSEBs are strengthened by mechanical compression and a 10% cement, lime, or bitumen stabilizer.

The equipment necessary to produce CSEBs could be a few wheelbarrows, shovels, buckets, screening frames, and a basic CINVA press, or fully mechanized, trailer-mounted hydraulic machines capable of producing hundreds of bricks per hour. Numerous presses, across the entire spectrum of cost and complexity, are available from manufacturers in the United States and around the world.

CSEBs are already a part of the New Mexico building code. CSEBs use far less cement than ICFs, require only enough wood for construction, and have the added advantage of using widespread masonry trades, as opposed to specialized labor. There are countless variations on block design, which allow for structural reinforcement or architectural details. CSEBs range in strength from 300 psi to greater than 1,200 psi, and will not rot, burn, or provide food to insects. Depending on your local soil characteristics, CSEBs can be produced on site, reducing cost and embodied energy. Given these characteristics, I would love to see some more detailed coverage of this building technology in the future.

Josh Denney • Atlanta, Georgia

Comments (2)

Lloyd Brown's picture

I think you're confusing the high-R-value wall structures (what the original article was talking about), with high-mass or high-thermal-mass wall structures. While there are benefits to both, the high-R-value wall has a much wider applicability across climate zones.

Essentially, a wall with high levels of insulation is able to resist the temperature difference between inside and outside. This is valuable for a high-performance home in all or nearly all climates, and is really just an extension of the well-understood, currently-constructed design of a modern home.

On the other hand, a high mass wall (eg. masonry, concrete, phase-change materials, water, etc.) are a completely different animal. It has very little insulation value (very low R value), which means that it can't support a temperature differential across it for very long. What it can do, though, is absorb a lot of energy, very slowly, with a fairly small temperature change. If you build your high-mass wall correctly, and in the correct climate, your wall will slowly warm up during the day, when the outside temperature is warmer than the interior temperature, and will then radiate that heat in both directions (inside and outside) at night, when the outdoor temperature is cooler than you'd want inside.

In short, high mass walls provide a temperature moderating effect. For an exterior high-mass wall to work well, this means that the average temperature over the course of the day, must be an acceptable indoor temperature. You essentially have to have a fairly wide temperature swing. In some parts of the US, this is fairly common, eg. in the desert Southwest, which is why the native people of those regions built with adobe for the most part. But if you're talking about the humid Southeast (eg. Florida), I don't think the nighttime temperature gets cold enough in the summer, for the average temperature to be acceptable. Similarly, in the northern US (eg. Wisconsin, Minnesota, parts of New England), the average wintertime temperature is far too cold to be acceptable.

Even in those regions, though, you could be clever, and put a high-mass wall inside a well-insulated building envelope. That way they work together to naturally keep the indoor temperature acceptable.

High mass walls are valuable, but please don't try to make them be something that they're not.

Bob Jordan's picture

I agree! CEB is very integrating and not as intuitive as one would first think. Heating and cooling costs can be significantly tempered with CEB, and Adobe construction can be blended for more ascetic options. Please encourage more Compressed Earth Block information. Bob, Dallas, Texas

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