Some products help us use other products or materials more efficiently. For example, drywall clips allow the elimination of corner studs, engineered stair stringers reduce lumber waste, and concrete pigments and polishing systems can turn concrete slabs into attractive finished floors. We also recognize some products, like vacuum plumbing systems, which use less material than their conventional counterparts. Many products with this attribute are fairly unique, so we bring a skeptical eye to manufacturer claims, but not a specific standard.
These products are environmentally attractive because they need to be replaced less frequently or their maintenance has very low impact, both of which can reduce costs as well as environmental impact.
Robust answers on typical service life of products can be hard to come by, however. In GreenSpec we reserve this criterion for products where the material is clearly more durable than alternatives, such as an exceptionally traffic-resistant polyurethane floor finish. We refer to standardized tests for durability when they are available and appropriate.
We also consider “appropriate durability”: long life is more important in a building envelope than in interior finish materials that will be replaced for aesthetic reasons. Here, reduced maintenance can be particularly important. An example is resilient flooring that doesn’t require regular waxing: an unnecessary use of resources and a health hazard.
TerraBuilt manufactures the GreenMachine, a compressed earth block (CEB) machine that presses tongue-and-groove bricks. Bricks produced by the GreenMachine have been tested to have a compressive strength of 900–2,240 psi, which exceeds relevant code requirements. The GreenMachine is available in two trailer hitch models, weighing 1 ton and 1.25 tons. The smaller GM3-10 runs on gasoline and produces 4"x8"x10", 20 lb. bricks at a rate of 4 per minute. The larger GM3-12 runs on diesel and produces 4"x8"x12", 24 lb. bricks at a rate of 5 per minute. The dimensional precision on all sides is 1/64". According to the company the blocks can be placed directly in a wall without any advance curing time and the tongue-and-groove design allows for mortarless installation.
Earthern unit masonry, including adobe bricks and compressed earth blocks (CEBs). can offer a variety of advantages over more mainstream construction techniques, such as timber frame or concrete. For one, it is commonly made onsite from readily available materials.
Adobe is a natural building material common to the American Southwest. It can be very durable if protected from erosion; many Native American adobe structures built hundreds of years ago are still standing. Made from soil that has suitable sand and clay content and then air-dried in the sun, adobe bricks typically have extremely low greenhouse gas emissions and embodied energy. Walls made of adobe bricks are most often protected from the weather with a parge coat of stucco or plaster, or large overhangs.
While adobe bricks are commonly made onsite without stabilizers, most commercially available adobe bricks are “stabilized” with portland cement or asphalt additives, adding to their expense, and depending on the proportion of stabilizer, adding significantly to their embodied carbon.
CEBs are a mixture of sand, silt, clay, and organic material, and can usually be made from soil at or near the building site. The addition of portland cement or another stabilizer may be recommended based on soil characteristics and performance needs, but this will add to the embodied impacts of the blocks.
Soil is loaded into CEB machines, which can typically press several thousand blocks per day. In addition to avoiding the impact of shipping materials to the site, this systems provides cost advantages, with avoiding purchasing and shipping costs.
The state of New Mexico developed a code regulating standard practices for CEB construction. The code technically only regulates construction in New Mexico, but is being used in other regions. When considering CEB construction, be sure to review the code and understand the important concepts, such as the difference between stabilized and unstabilized CEB, and when each are appropriate.
Due to the relatively low impact of these materials and construction methods, GreenSpec lists adobe blocks and related products, as well as CEB presses.
Ratings and Commentary