These days there are more options than ever for those seeking to minimize the negative environmental impacts of building a house. Just as many backyard gardeners are willing to make an extra effort to grow their own produce organically, many prospective home builders and buyers are expressing a desire to live in a house that is distinctively healthy, both for the residents and for the surrounding ecosystem. From foundation to roof and from masonry to finishes, there are now manufacturers and merchants providing nontoxic, sustainably made building materials and house wares. These may be products created by high-tech innovation or made of traditional, plant-based ingredients that are beautiful, durable, and healthful.

I have been a longtime editor for the book publisher Chelsea Green, and over the past ten years I've edited more than a dozen books about natural building techniques and energy-efficient design and construction. When my wife and I built our own home, we made every effort to apply a tenet that runs like a refrain through all of the books I've worked on: Build as small a house as possible.

More important than which building materials and home furnishings you choose is the scale of your project. The burgeoning world of "natural building" is so earnest and well-intentioned that it sounds like sacrilege to say so, but an 800-square-foot, pre-fab trailer could actually have less negative environmental impact over time than a 3,000-square-foot, timber-framed, straw bale house with a solar-electric system. In a global context, an asphalt-sheathed shanty on the outskirts of Mexico City probably has a far lower negative environmental impact overall than a conscientiously crafted eco-mansion in suburban San Diego.

In his book The New Independent Home (Chelsea Green, 1999), Michael Potts ruminates upon what he calls our "Edifice Complex": "In the last fifty years, American houses have doubled in size while family sizes have dwindled. Modern houses are twice as big as necessary, and thus more expensive to build and keep comfortable. Commodity housing makes large, even grandiose gestures toward habitability without managing to create homeyness: two-story entries, unused rooms, wall-to-wall carpet, long hallways, enormous picture windows, all contributing to ‘curb appeal' or the attractiveness of home-as-commodity when viewed from the street. Starting in 1978, in reaction to the rising cost of comfort, houses have been built like space capsules, tightly sealed to conserve heat, isolated from the outside environment, but certainly not made any smaller!"

For several years, Arizona-based carpenter and writer Shay Salomon has been researching two counter-trends — bigger and bigger conventional houses vs. more and more creative use of smaller spaces by people who have realized that living more lightly in terms of house-size and complexity has great economic and quality-of-life benefits as well as ecological benefits. Salomon edited a special issue of the natural-building journal The Last Straw exploring these questions.

Contrary to the conventional wisdom that asserts, Whatever space is available will get used, therefore build the biggest house you can imagine needing, since it's easier and cheaper to do that at the outset than remodel . . ., the new, unconventional reasoning goes more like this: Since unnecessary space is costlier in materials, construction, maintenance, and energy expenses than essential space — and since labor, materials, and energy cost more when purchased with borrowed money — build the smallest house you can anticipate being comfortable in, minimizing reliance upon exotic materials, and labor-, time-, and energy-intensive construction methods, and with the smallest mortgage possible.

Vermont contractor Sam Clark writes in Independent Builder (Chelsea Green 1996), "The building industry is always promoting larger space, and different kinds of spaces come and go in popularity. At one time ‘family rooms' were emphasized in suburban homes. Today the industry is pushing more and bigger bathrooms, home offices, master bedroom suites, and exercise rooms. The most obvious way to conserve land, energy, and building resources now, and fuel in the future, is to build smaller houses. A small house uses less land, less heat, and less materials. It causes less pollution at every stage. Its economies are more than proportional to size, because a small house needs not just fewer timbers but smaller ones, since the spans are shorter. This is a point often ignored by people who talk about ‘sustainability.'"

The more materials you use, whatever their source, the more impact the building will have. Using Department of Labor statistics, architect Pliny Fisk has painstakingly tracked the nationwide and international ripple effect of building an ordinary American tract house in an economy where trees are harvested in Oregon then shipped to Japan for milling, and where individual components of a manufactured item originate in dozens of different locales. Yet given the plethora of "green" building products now available, isn't it reasonable to think that homes can now be built larger and still qualify as ecological?

The implications of using any particular building option should be viewed in successive stages: from initial extraction and processing, through manufacture, installation, maintenance over time, eventually to removal, replacement, and disposal. Each of these stages has a monetary cost, and each step requires investments of energy and labor. Likewise every step generates a certain quantity of waste. Ecological designers have devised a measure for the cumulative investment of effort and ingredients, referring to a material's "embodied energy."

An example of a material high in embodied energy is steel, which requires huge amounts of energy and effort for extraction, processing, and manufacture. Steel is also highly recyclable, retaining its value over time. An example of a comparatively low embodied-energy material is the gravel or sand used in foundation drainage, if available close to the site; not highly refined, these materials are used in a form close to their "natural" state, unless they need to be trucked great distances, in which case their embodied-energy quotient rises significantly.

The concept of embodied energy — which reflects not merely a particular material's or product's "sticker price" but more broadly its ecological cost to society and the planet — is an important tool in evaluating building options. In ecological terms, it is a good idea wherever possible to use lower embodied-energy sources (including minimal transport) for virgin materials, and to use recycled sources for high-embodied energy materials.

Many builders of ecological homes like to use salvaged materials, since these carry a resonance of our artisan forebears while remaining very serviceable as building components. For our house we were lucky to find an old summer camp that was being razed to make sites for new homes. For a payment of $50, the demolition company gave us and several other families access to the camp buildings for three days, during which time we retrieved tongue-and-groove paneling, electrical outlets, bathroom fixtures, and — best of all — the bricks from half a dozen chimneys. When our mason built our new chimney, he praised these old, hand-drawn bricks for their hardness and quality, noting that they had already been used for at least two previous chimneys. According to Jennifer Corson, author of The Resourceful Renovator (Chelsea Green, 2000), "Brick is one of the oldest — and simplest — of building materials." On the other hand, as Corson writes, "A tremendous amount of fossil fuel energy is expended . . . to produce one common brick . . . equivalent to that needed to produce approximately 1.2 feet of 10-inch steel beam from 100 percent recycled steel." So with its high embodied energy and great recyclability, it makes great sense to reuse brick, which degrades very little over time and increases dramatically in aesthetic value.

Coming back around to that critical question of size: while building with recycled materials such as brick saves money and energy, to benefit from these savings a builder needs to tailor the scale of the brickwork to the readily accessible supply of high-quality recycled bricks. The challenge of building a smaller house becomes a kind of puzzle: How much house can be built by staying within a "budget" of locally available, affordable, and high-quality salvaged, recycled, or low-embodied-energy materials? In other words, you start your design process with the pool of affordable, readily available materials — and with a firm financial budget — instead of with a list of rooms and a floor plan.

Another invaluable principle in understanding building options is the concept of life-cycle cost, projecting energy and maintenance expenses over time. With a house, a hundred years is a reasonable duration for such calculations. On the spectrum described above, local stone has lower embodied energy and is more aesthetically pleasing than trucked-in concrete. However, concrete foundations require less maintenance and are much more energy efficient. Using the hundred-year life-cycle rubric, the concrete foundation, despite its higher initial cost, in nearly every case would be more economical.

While embodied-energy and life-cycle analyses can help with materials selection and design choices, as I continue to emphasize the single most important determinant of environmental impact is ultimately size. Although ecological materials are almost always more environmentally friendly than petrochemical-derived alternatives, opting for a salvaged post-and-beam frame or milk-based paints does not necessarily constitute green construction.

Here's another comparison, using light bulbs. One compact fluorescent bulb costs more at the checkout counter than one incandescent bulb, but lasts almost ten times longer and uses one quarter of the electricity to produce the same amount of light. Even so, a 4,000-square-foot "green" home utilizing scores of high-tech compact fluorescents would use far more energy than a modest, 1,000-square-foot home using incandescents prudently. We see the same problem with automobiles: emission-standards and technological improvements reduced pollution, but the standard size of cars has been increasing steadily, obliterating the benefits of better gas mileage and pollution controls.

In addition to the ethical and global-ecological advantages of building adequately sized but compact homes, the economics of building smaller than today's standard are intensely compelling. Before determining floor plans, and before drawing up comprehensive shopping lists of materials, and even before choosing a contractor or deciding to build the house yourselves, think carefully and methodically about how construction of your home will be financed.

As Rob Roy explains in his brilliantly sensible book Mortgage-Free! Radical Strategies for Home Ownership (Chelsea Green, 1998), a 25-year bank loan for $36,500 at 10% interest will necessitate twenty-five years of payments and a total expense of $99,504. Mortgages have become so common, and so many of our friends and relatives have routinely surrendered years of their working lives to repayment of high-interest housing debts, we often fail to recognize the enormous advantage of designing a home around the minimization of debt and a "pay-as-you-go" construction process with coherent, staged advances and pauses.

For most people, scaling down a project to reduce the mortgage load will have corollary benefits, imposing a certain discipline on materials selection and architectural features. A compact, energy-efficient structure can also be the most affordable (and enjoyable) form of home.

Builder Paul Lacinski, of GreenSpace Collaborative in Massachusetts (co-author of Serious Straw Bale, Chelsea Green 2000), notes that "Unless you are quite well off and have unusually modest needs, some conflict between what you want in a house and what your budget can reasonably support is inevitable. ‘The best possible house for the available money' almost never means ‘the largest possible house for the available money.' A steel industrial building will probably always be the largest space available for any given amount of money, but would you want to live in one of those? A house that is enjoyable to build and consistently enjoyable to live in will strike a balance between size and character, between quantity and quality of space. The starting point of a good design process is to simplify your needs. If you begin with the intention of building small and simple, you can add amenities as the budget firms up. That process prevents you from wasting money on wants disguised as needs and prevents stretching the budget thin on unnecessary space; this keeps the quality of the space high, and saves on heating and maintenance costs."

If from the earliest stages of your planning process you can keep firmly in mind that each choice you make involves both ecological and financial costs, you may well find that structuring your project to minimize both negative environmental impacts (pollution, waste, inefficiency) and financial servitude results in a much more "sustainable" home than one designed according to the latest fashions in eco-natural products.