The Difference between "Green" and "Sustainable"

The idea of energy efficient, healthy buildings has been around for a long time, so why is just now that the concept of "green" or "sustainable" building is entering the mainstream and catching the attention of fortune 500 companies like Wall Mart, Dupont, and Home Depot? There are probably several reasons; Global Warming, rising energy costs, the growing awareness and liability costs associated with "Sick Building Syndrome”, declining oil reserves, and concerns about our limited water supply. The list goes on, but whatever the reason or reasons, sustainable building is a concept whose time has come.

Which begs the question, what is IT? The ultimate definition depends on how one defines "green" as opposed to how one defines "sustainable".

My personal definition of "green" is relatively simple. A home's design is “green” if its serves to reduce many of the harmful impacts buildings have on our environment and our home's inhabitants. So "green" home design revolves around four key issues:

1. Designing for energy efficiency including the use of renewal energy sources such as wind, geothermal, and solar.

2. Creating a healthy indoor air environment with adequate ventilation and making material choices that minimize volatile organic compound (VOC's) outgassing within the home.

3. Specifying building materials and resources that are sustainable, have low embodied energy, and produce a minimal amount of upstream environmental impact.

4. Providing for the efficient use of water via appliance, faucet, and shower head choices and in arid climates by zeroscaping and recycling grey water and capturing rain water for landscaping and other non-potable uses.

However, the words "green" and "sustainable" are often used interchangeably, and sustainable has a more precise meaning that is often obscured, distorted, and dilluted by the commercialization and marketing of the green "movement". In the context of our built environment sustainable takes its meaning from "sustainable agriculture", or "the ability ... to produce food indefinitely, without causing irreversible damage to ecosystem health".

If we accept this as the basis for the definition of sustainable building everything changes. For example, a 5,000 SF home with a HERS index of 70, bamboo floors, and Energy Star appliances may be "green", but it is NOT sustainable. In the context of Global Warming and even the most optimistic projections of Peak Oil and Gas, only a home that meets zero energy standards can be considered sustainable.

Borrowing from A. A. Bartlett's Laws of Sustainability, here are my own Laws of Sustainable Housing.

1st Law - U.S. urban sprawl and the growth in home sizes and the associated energy and resource consumption is not sustainable.

2nd Law - Retrofitting over 100 million (energy inefficient) homes in American to a condition of sustainability will be a monumental task.

3rd Law - In the context of Global Warming and even the most optimistic projections of Peak Oil & Natural Gas, new and retrofitted homes should only be built to net zero energy standards.

4th Law - The size of population that can be sustained (the carrying capacity) and the sustainable average size and resource consumption of our homes are inversely related to one another. In other words, if the population increases the size and resource consumption of our homes must decrease to achieve a sustainable balance.

5th Law - The U.S. cannot sustain average home sizes that are more than twice the average size of other developed countries.

6th Law - All countries cannot simultaneously be net importers of carrying capacity(fossil fuels, etc.).

7th Law - The importation of such a large percentage of our energy carrying capacity makes the current U.S. standard and pattern of building extremely vulnerable.

8th Law - The benefits of suburban sprawl accrue to the developer and auto companies; the benefits of poor energy efficiency and standards accrue to energy companies and utilities; but the costs are borne by us all.

9th Law - Inadequate U.S. building energy standards are contributing to a rapid depletion of our natural gas and other fossil fuel resources. This is true not only within our borders but via our high level of imports, it is true worldwide.

10th Law - Net zero building energy standards will be necessary to slow the depletion of fossil fuels in a pre and post Peak Oil and Gas world.

11th Law - Converting our existing housing stock to a much higher energy standard will be completed negated by even a modest growth rate in new homes, however energy efficient those new homes may be.

12th Law - Smart residental growth is an oxymoron.

13th Law - Building should restricted on prime agricultural land. The highest and best use of land is for agriculture, especially to local food supplies.

14th Law - Energy shortages due to peak oil and gas will slow and then eventually stop housing growth and force the transformation of our existing housing stock.

15th Law - People living in slums don't care about sustainable housing.

16th Law - The addition of the phrase “sustainable housing” or “sustainable development” or “green building” to our vocabulary is not sufficient to ensure that our built environment becomes sustainable.

17th Law - The current state of our green, sustainable building “movement” may amount to nothing more than rearranging the deck chairs on the Titanic.