June 4, 2000

High Efficiency Houses
By Royce Carlson

Paper and old car tires are among the materials being used these days in experimental home construction. Since the 70ís there has been an increasing amount of creativity going into alternative building materials with an eye toward energy efficiency and recycling. The Earth Ship system is one that works toward both of these ends by using recycled automobile tires to produce thick mass walls that help reduce energy costs. More than just unique building materials, an Earth Ship is an entire living system designed to be light on resources as well as an interesting and esthetic architectural design to live in. Donít try one in Arizona, though. Youíll cook.

The design features south-facing sloped glazing that is supposed to provide passive solar heating. It definitely does that! In southern climates, however, sloped glazing will let heat enter in the summer as well as winter and summer indoor temperatures can become unbearable. Other than this design flaw for warm climates, the Earth Ship is a great idea in creating a house that operates as an efficient system.

Another recently developed building material is papercrete or fibrous cement, made of paper pulp and a small amount of cement cast into bricks and used to build high R-value walls while recycling used paper in the process. The recycled paper is shredded and converted to pulp in a cement mixer-like apparatus. The paper slurry is poured into molds much like adobe brick molds and then the bricks are laid up into walls. They are surprisingly water-resistant but still need to be protected from weather by the overhang of a roof. They provide tremendous insulation values while using materials that would usually end up in a land fill.

Straw bale construction is all the rage among the alternative building community. Once again an easily renewable resource, straw, is used to build thick, highly insulated walls to produce an extremely energy efficient house. The straw bales are stacked on a foundation and staked through with re-bar. Usually post and beam construction provides the support for the roof so the straw bales donít really provide support. The straw is plastered inside and out with stucco, thereby sealing the straw away from rodents and rot. There are houses in the Great Plains built out of straw bales a hundred years ago that are still standing.

Earth construction has seen some relatively recent developments. Rammed earth was developed some years ago and involves packing a mixture of dirt and sand very tightly by pounding it into forms using minimal water. This produces a surprisingly strong sandstone-like material. The problem is that it is very labor intensive to produce rammed earth walls. More recently a new process called Poured Earth has been developed using a mixture of earth and sand plus a small amount of gypsum as a binder. The gypsum has a retarder added to it to extend the setting time. The mixture is poured into wall-forms like a thick milkshake and sets up fairly quickly into strong, thick mass walls. Coloring oxides can be added to the material as it is poured to produce some absolutely beautiful effects.

There are experiments in alternative building going on all over the world. I have touched on only a few of the processes, the ones I am most familiar with. To explore this fascinating subject further, please visit the Zenzibar Alternative Culture Alternative Building and Construction category.

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