In the latest issue of The New Yorker, writer David Owen looks at a troubling potential conundrum of energy efficiency: the "rebound effect". The more efficient our cars, refrigerators and air conditioners become, the more of them get produced, and so the actual reduction in energy disappears.
There are all kinds of examples throughout history.
The Ford Model T, manufactured between 1908 and 1927, averaged between 13 and 21 miles per gallon. A century later, we've learned to use gasoline much more efficiently, but that has only led to bigger cars stuffed with energy-sucking electronic gadgets.
A refrigerator sold in America today uses three quarters less energy than the 1975 average, even though it is one-fifth larger and costs 60 percent less. Yet during this same 35-year time period, the global market for refrigeration has grown exponentially; moreover, far more people in the US now have a second fridge or freezer.
On a macro scale, this proves out too: Between 1984 and 2005, electricity production grew by about 66 percent despite economy-wide energy efficiency gains. Some of this can be attributed to population growth, but not all. Per-capita energy consumption rates also increased during this period, even though energy use per dollar of Gross Domestic Product fell by around 50 percent.
Owen's article is largely based around an idea called the "Jevons paradox" that dates to an 1865 book by Englishman William Jevons called "The Coal Question". At the time, Great Britain was the world's leading industrial, military and economic power. But Jevons argued that it couldn't last. The country's coal supply was rapidly depleting, and he postulated that even increased efficiency in the use of coal would not delay the process. "It is wholly a confusion of ideas," Jevons wrote, "to suppose that the economical use of fuel is equivalent to a diminished consumption. The very contrary is the truth." The more efficiently we use power, the more power we'll want to use. This is also commonly known today as the rebound effect.
All this begs the question: what about buildings?
After all, few entities have been the focus of energy efficiency goals more than buildings. Together, homes and buildings consume more than a third of total energy used in the United States today. Locally and regionally, organizations like the Northwest Energy Efficiency Alliance (whose BetterBricks wing is a Portland Architecture sponsor) have devoted millions of dollars to designing new buildings and renovating old ones so that less energy is consumed. And the design community has become a national leader in sustainability. Portland has more LEED-rated buildings than virtually any other American city, especially when you measure it on a per-capita basis. The first LEED Platinum-rated condo, large medical facility, and National Register-listed building are all located here.
Energy efficiency is also part of a national strategy, called "the fifth fuel" after coal, petroleum, nuclear, and renewables. In 2007 the United Nations Foundation called energy efficiency gains "the largest, most evenly geographically distributed and least expensive energy resource."
Is it a waste of time, energy, money and resources to design and build buildings with better insulation, more natural light, and smaller mechanical systems? I'm not completely sold on the Jevons paradox as it relates to architecture today, nor are experts unanimous about its relation to other current energy issues.
For starters, as explained to Owen by Lee Schipper, a senior research engineer at Stanford University's Precourt Energy Efficiency Center, the rebound effect is minimal because energy is a relatively small part of the overall economy, between six and eight percent. Efficiency gains today have much less power to stimulate consumption than industrial manufacturing gains in the 19th century like Jevons wrote about.
More specifically as it relates to architecture, building green needn't be seen as a stimulant to building more. There is, perhaps, an argument that in our drive to weatherize homes we will spend as much energy on manufacturing and transporting new materials as will be gained from reduced heating and cooling. But what are we going to do, stop fixing up our buildings or building new ones?
The one area in architecture where the Jevons paradox could hold true is with air conditioning. Just as there are more refrigerators and freezers in use both overall and per capita today, wiping away much of the efficiency gains made from appliances using less energy, air conditioning is much more prevalent than in previous generations. It's part of the reason that regions and cities with very warm climates like Arizona and Nevada and the South saw large population influxes over recent years. Then there's the international spread of air conditioning to developing countries. According to Owen's article, between 1997 and 2007 the use of air conditioning in China tripled. In india it's expected to increase almost tenfold between 2005 and 2020. Owen cites a 2009 study saying air conditioning already accounts for 40 percent of the electricity consumed in metropolitan Mumbai.
Even so, the rebound effect with air conditioning - overall use eating up efficiency gains - is not an argument for the ineffectiveness of green building and architecturally oriented energy efficiency. On the contrary: if millions more people are using AC, it's even more important that this happen in buildings with tightly sealed thermal envelopes (without leaks, in other words) so the AC be utilized as efficiently as possible. Therein, perhaps, lies the broader answer with questions of the rebound effect. Maybe it does exist, to a degree, but if so, that's an argument to fight for efficiency gains all the more.
If there's a lesson to be learned from hashing over the Jevon paradox and the rebound effect as it relates to energy efficiency, perhaps it's a matter of re-learning a bit of common sense: all the efficiency gains in the world don't matter if we don't also curb demand. And yet reducing demand is the last thing any economist wants to hear. The 2000s decade was largely about creating exponentially larger demand for real estate by relaxing home ownership financing rules. And even if we hadn't got carried away building new suburban cul de sacs and urban condos over the last ten years, the population here and especially in other countries continues to increase. All those bodies need electricity of some sort.
Yet there are things we can do on the demand side. Jimmy Carter was the last American president, more than three decades ago, to tell us to be smart about little things like turning the lights off in rooms we don't occupy. Behavior can be adjusted on the macro level, and that's as important as technical advances in efficiency. It's just that having more efficient air conditioners, TVs and refrigerators has to be coupled with anti-sprawl planning, mass transit, and other factors. And then there's the question of energy taxing. Price is as much a determinant of energy or other product/service use as efficiency. As even Jevon would have acknowledged 135 years ago about coal, how efficiently we use anything is merely an extension of how much we want or need to use it.