How to Choose Green Building Materials
Typical wood-frame building methods are wasteful, inefficient, and far from eco-friendly. Several natural construction methods offer greener alternatives to using wood and may be the best choice for your green dream home.
Check with your local building department before beginning a natural construction project. The building codes favor wood, steel, and concrete, and if you want to use something else, you may need special approval from the building department.
Some of the materials and methods of green construction include:
Straw: The thick walls of a straw-bale building have become synonymous with the green building movement. Bales of straw from the harvesting of wheat, oats, barley, rice, rye, or flax are stacked on bamboo or rebar stakes to make walls with an insulation value that’s often triple that of a wood-frame home.A straw bale wall sits on a foundation and is sealed inside and outside.
Cordwood construction stacks up short, round lengths of wood into a wall. Using what would normally be cast aside for firewood, cordwood looks like a stack of wood you’d have behind your fireplace with the ends of the logs exposed. The cordwood is held together with mortar, creating a wall with both high insulation and high thermal mass.The random stacking of wood in a cordwood wall creates a beautiful pattern.
Earth: Clay, dirt, sand — several types of green building methods use various types and combinations of Mother Earth’s own materials, making them very green and completely fireproof.
Adobe construction is used most often in drier, sunny regions, such as the American Southwest, where it’s relatively easy to dry the bricks of mud and straw. Though the resources are right at your feet, the drying and stacking make building with adobe time- and labor-intensive.In an adobe wall, the mud bricks are stacked up and capped with a concrete beam, which helps spread the weight of the roof and ties all the walls together.
Ceramic earth is like a giant ceramic kiln. Constructed with adobe with very high clay content in either bricks or tubes, the finished walls are fired in place to become hardened ceramic. These permanent, waterproof, and earthquake-resistant homes use all four natural elements: Earth and water to make the bricks and fire and air to finish them.In a typical ceramic earth wall, the tubes are coiled like a ceramic pot.
Cob is a mixture of clay, sand, straw, water, and earth, which makes it very similar to adobe, but instead of being formed into bricks, cob is built up a handful at a time. Requiring little money or skill, a cob home can be built by homeowners willing to get their hands dirty.
Rammed earth is essentially just man-made stone. Rammed earth walls are formed by packing, or tamping, a mix of soil with a tiny amount (around 3 percent) of Portland cement, which acts as a binding and strengthening agent, within a two-sided form. The finished rammed earth wall is nearly as strong as concrete.In a rammed earth wall, earth is placed one layer at a time into large forms to create massive walls.
Pneumatically Impacted Stabilized Earth (PISÉ) creates a beautiful wall that shares the beauty of rammed earth but is much less labor intensive. A one-sided form is placed over the building foundation and a watery mixture of earth and Portland cement is sprayed onto this form. Wielding the pressure hose requires some expertise, so this is not a do-it-yourself endeavor.Layers of mud sprayed into a form create PISÉ walls.
Earthship walls are earth-filled tires set into the ground — a simplified form of rammed earth in which discarded tires become the form into which you pack the dirt. The house is buried on three sides with the side open to the sun designed to allow it in during the winter and keep it out in the summer. An Earthship heats and cools itself without consuming any fossil fuels.In a typical Earthship home, old tires are packed with dirt and stacked to make walls. The windows are located toward the sun to keep the building warm in the winter.
Most earth-made buildings are coated with plaster, stucco, or a sealant, which helps them shed water and remain insect-proof.