What Type of Eco-Home Is Best For You?

Enlarge Image Image Gallery A house in the grasslands near Walden, Colorado, features straw bale infill walls with a post-and-beam support structure. Locally harvested and milled lumber and straw create thick, highly insulated walls to help keep out harsh winter winds. Joe Coca

Building ecologically means living in harmony with a particular place and the systems that exist there. The key is to explore the architecture, materials and methods that will work in your climate. Consider those that support natural heating and cooling, are locally available and will work within your budget, taste and lifestyle. The first step is exploring who and where you are.

What’s your comfort zone? 

“Thermal comfort” is about feeling warm in winter and cool in summer. Study the chart on page 63 for appropriate responses to your climate, then look at how your site may influence the available choices. For example, if your property is on a north-facing slope in dense forest, passive solar heating may not be the best strategy no matter what the regional climate is.

All building materials have inherent properties that can support or thwart your thermal comfort strategy. Two important and often misunderstood characteristics are thermal mass and insulation.

THERMAL MASS, a material’s capacity to absorb and release heat, is valuable for both heating and cooling. Earthen materials such as stone, adobe, rammed earth and concrete are high in thermal mass. Thermal mass can help moderate your home’s temperature by absorbing heat when it’s hot and releasing it when it’s cool.

INSULATION is a material’s ability to slow heat passage—the more insulation, the more slowly heat travels through it. Whereas thermal mass tends to be dense, insulation is light and fluffy; the trapped air pockets do the insulating. Too little insulation means your home will lose heat in winter and gain it in summer.

Earthen homes

Earth, one of the oldest and most widely used building materials, can be highly durable, and it’s available almost everywhere. Earthen walls are usually thick, dense, high in thermal mass and low in insulation value. Because of its clay content, earth absorbs and releases moisture, helping to balance humidity in the home. The cost of building with earth can be dirt cheap if you do it yourself but very expensive if you pay others.

ADOBE is made of sand, clay and fibrous material (straw, etc.) that is dried or baked to form bricks, then stacked and mortared to make walls. “You can make an adobe block almost anywhere. It’s so cheap, anybody can do it,” says engineer Bruce King, who is writing an earthen construction building code through his Ecological Building Network (www.EcoBuildNetwork.org).

RAMMED EARTH is made by compressing a damp mixture of earth, sand, gravel, clay and sometimes a stabilizer (cement, for example) into structural forms that are stripped away after the walls have solidified. It creates a durable, stonelike, monolithic wall. “Rammed earth is a beautiful finished product when installed by experts,” says architect David Easton, who has been championing the material for decades (www.RammedEarthworks.com).