Notes from Windward: #64
Sustainable Construction Department
Most of the construction techniques used to create housing and work space can be thought of as "hard technology" in that they involve bulldozing a building site, and then bringing in a crew of highly paid professionals to create a structure out of virgin materials trucked in from all over. And when it's all over, you're left with a building that requires both a lot of energy to operate and a lot of income in order to pay the thirty-year mortgage.
By way of contrast, sustainable construction, also called "soft technology," focuses on owner built designs that use locally available materials. Here's an example of how we're incorporating the sustainable construction technique of compressed earth bricks into our cabins.
Our conditional use permit authorizes the construction of eight cabins laid out in a semi-cricle around the main area where the dining hall and the solar greenhouse are located. Over the past few years, we've installed most of the infrastructure needed for the first four cabin sites which are located on the western side of the semi-circle.
The pads that the cabins will be built on have been cut back into the slope of the hill so that we can take full advantage of an earth-sheltered design to insure that the main floor is warm in the winter and cool in the summer. The next step is to dig a twenty-foot wide notch back into the hill in which to locate and build the retaining wall that will from the back and sides of the first floor of the cabin.
All in all, we're talking about excavating some 320 cubic feet of dirt per cabin. Usually, the excavated dirt would be used to fill in some other part of the landscape, but in this case, we already know the texture of that soil and that it will make good CEB bricks which we'll then use to veneer the parts of the cabin where the retaining wall would otherwise be exposed.
The retaining wall will be cast as a single piece using interlocking foam forms. These three foot long foam pieces snap together to create a wall that looks like it's been made from over-size foam "cinder blocks." Once the forms are in place, we'll bring in a concrete pumping truck that will fill the forms with concrete made from rocks that are three-eighths of an inch or smaller, and once it sets, we'll have a monolithic retainingwall that's already insullated inside and out.
The back wall will get a membrane to keep out ground water, a drain pipe to route ground water away from the building's foundation. Then the wall will be backfilled and we're done with that part of the cabin.
The front side of the cabin needs some sort of surface treatment to cover up and protect the foam insulation; that's were the CEB bricks come in.
As dirt is excavated to make room for the cabin, it's laid out to dry, after which it's run through a sieve to remove roots and leaves. Then about twelve pounds of dirt is mixed with one pound of Portland cement, and just enough water to hold the mix together - you have to go easy on the water because too much water at this stage will weaken the finished brick.
Then a measured volume of the soil/cement mix is put into a steel mold, and a ten-foot long lever arm is worked to compress the mixture into a Compressed Earth Brick.
The "green" brick is set in the shade under wet burlap where it will begin the damp, month-long curring process which will ultimately yield a brick with strength comparable to a traditionally fired brick.
When the cabin is finally faced with the bricks made from the earth in which it is nestled, the structure becomes an embodiment of sustainable construction. By building with a material found right at the building site, the process uses what is already at hand instead of something which would have to be trucked in from a long distance at considerable expense.
There are many different sustainable construction techniques, and we look forward to utilizing as many of them as practical, in part because the different options demonstrate the many ways that quality, sustainable housing can be created by ordinary people doing ordinary things. Naturally, not every possible technique will be appropriate to our local and climate, but every locale has a variety of ways that renewable and sustainable practices can be used to provide a quality lifestyle without the wholesale use of factory manufactured components.
That isn't to say that some of those factory produced components aren't worth including in sustainable construction; products like the modern vinyl double-pane windows go a long way towards appropriate levels of energy efficiency, and are a wise energy investment, but other products such as compressed earth bricks can increase the operational value of a dwelling without significantly adding to the either the financial or environmental cost usually associated with new construction.
Cord-wood construction is another sustainable construction practice we look forward to incorporating into our community room design. That building will be a large, round pole-barn design with sixteen inch thick cord-wood walls.
For a discussion of Windward's Land Management Department, Click Here
Notes From Windward - Index - Vol. 64