What Is An “Ecological House”?

 Written by Philip S. Wenz, 2007

Do you want to live in an environmentally friendly house, but wonder what that really means? Does your house have to be loaded with expensive “green” gadgetry, or built with recycled tires? Is it practical to retrofit your existing house? Will your new “eco features” help the environment, or are they just more stuff to consume — trendy, but ultimately damaging to the planet?

Though there is no single, set definition of an environmentally friendly house it's good, at the outset, to think about what you're trying to accomplish. I've found the concept of the “ecological house” — new or retrofitted, big or small — useful for determining project goals.

An ecological house is modeled on the energy and material flows of natural ecosystems, and thus enhances rather than degrades the environment. Like an ecosystem, an ecological house conserves resources (energy, water, food and materials). It also produces resources, or at least gathers and stores more of them than it uses. The “extra” resources are distributed back into the larger environment to support life elsewhere.

A standard house, by contrast, is a resource sink. Life's essentials flow into it, are dissipated or degraded until useless, and are dumped off into the environment, sometimes as toxic waste. The flow is unidirectional, from source to sink to waste.

In an ecosystem, and in an ideal ecological house, there is no waste because the resource flow is circular. Like houses, ecosystems import energy — mostly solar, in their case. Unlike standard houses, however, ecosystems store their energy and reuse it. It's stored first as plant biomass, which is eventually distributed as food to the ecosystems' myriad inhabitants. Further, and this is the real key to the sustainability of ecosystems, the stored energy continues to circulate, as exchanged nutrients, until it makes its way back to the plants. In the scenario known to every sixth grader, plants make animal food and animals make plant food.

Ecologists and ecological designers describe this behavior of ecosystems as the closing of nutrient loops. Human habitation systems — from cities to houses — create one-way energy and material flows, leaving loops open. Ecosystems unconsciously practice the “reduce, reuse, recycle” dictum and have sustained themselves for billions of years. Human systems have been around for only a million years or so, and might not exist much longer if they don't start conforming to nature's rule that “waste equals food.”

How can you mimic nature and close a loop at your house? Compost your food scraps and use them to grow a garden. The standard, open-loop approach to consuming food eliminates nutrient-rich scraps as waste, which requires energy in the form of a garbage truck for disposal. If you turn your unused organic material into plant food and use the sun's energy to produce human food, you've closed a loop and reduced your family's demands on the larger environment.

As well as circulating nutrients internally, ecosystems contribute to life in their region and the biosphere by releasing unused food, water and minerals into their surroundings at appropriate times. Similarly, a “home ecosystem” can redistribute a resource such as “gray water” — for example, shower water, which is clean enough for certain uses — and store that water in plant tissue, say, in fruit trees grown on the property.

At harvest time, some of the water is circulated back to your family as fruit, closing a local loop, and some is expired for healthy recirculation in the atmosphere as the leaves dry up and drop off (as opposed to unhealthy and energy-intensive treatment in a sewage plant). The dried leaves, of course, can be used as compost and mulch for next year's vegetable garden.

The possibilities for creating intertwined closed loops are endless.

Using nutrients from your yard, you can profitably grow products ranging from hardwoods, bamboo and herbs to exotic fish. Your house can produce more electrical energy than your family uses and direct the excess to environmentally benign applications, such as heating a food-producing greenhouse in winter. Or, you can feed the public utility grid for credit toward your monthly bill.

The ecosystem model can be applied to all of the fundamental issues in ecological design. For example, optimizing a house's “life cycle” — the amount of energy and material needed to create the building, its ongoing demand on the environment and its final disposal—can be facilitated by observing how ecosystems use local resources and recycle materials. Nature herself is your best guide to designing and living in your ecological house.