I’ve long appreciated the adage that you can’t manage what you don’t measure, so I’ve spent a good bit of time looking at numbers — especially relating to energy. (Apologies in advance to readers who don’t think quantitatively.)
One of those numbers that I’ve always been intrigued with is how much of our nation’s total energy consumption relates to buildings. That sounds simple enough.
We are fortunate in the United States that the Department of Energy (DOE) tracks all sorts of energy statistics through the Energy Information Administration (EIA), so a numbers geek can go hog-wild digging as deep as he might want into whatever aspects of energy production and consumption are of interest.
On the energy consumption side, the most common breakdown of end uses is Residential, Commercial, Industrial, and Transportation. The EIA shows the 2011 breakdown of these end-uses as follows: residential 22%; commercial 19%; industrial 31%; and transportation 28%.
In units of energy, total U.S. primary energy consumption in 2011 was 97.3 quads (one quad equals one quadrillion Btus — that’s 1 followed by 15 zeros). Of that, the residential sector totaled 21.6 quads, commercial 18.0 quads, industrial 30.6 quads, and transportation 27.1 quads.
Site energy vs. primary energy
These fractions and quads are of primary energy use. When we use a kilowatt-hour (kWh) of electricity for lighting in our homes, that’s a kWh at our house (site energy), but to produce that kWh of electricity probably took about three kWh of primary energy. The difference between site energy and primary energy is due to waste during the production and delivery of energy to our end-uses. With electricity that difference is huge, due to waste heat produced in power generation and losses in transmission. With other energy sources, such as petroleum or natural gas, the difference between primary and site energy is much less.
So, when we look at this end-use split (22%, 19%, 31% and 28%) we’re looking at the primary energy, and 41% of that (22% + 19%), as commonly argued, has to do with buildings. So far, so good.
Having 41% of U.S. energy consumption attributed to buildings is huge. A very similar metric has to do with greenhouse gas emissions. The percentage is slightly different — because some energy sources are more carbon-intensive than others — but the difference is minor. Buildings account for 40% of total greenhouse gas emissions in the U.S. (usually reported as carbon dioxide or carbon equivalents).
These numbers tell us that we need to be paying a lot of attention to buildings if we want to make headway in curbing our contributions to climate change.
Building-related energy consumption is actually a lot greater
But, I contend that buildings and development patterns actually account for significantly more energy consumption and global warming impact than these numbers suggest.
With the other two segments of energy consumption in the U.S. — industry and transportation — buildings and our development patterns also have a big impact.
Some of the industrial sector energy consumption has to do with heating, cooling, and illuminating factories. Digging deeper into the EIA energy consumption data for 2011, we find that heating, ventilation, and air conditioning (HVAC) accounts for 0.7 quads, and facility lighting 0.2 quads. Those energy uses, I suggest, really fall into the area of building energy consumption (as opposed to the process of making steel or glass, for example).
There is also a portion of industrial energy consumption that has to do with construction materials — the energy it takes to make the stuff we use in buildings houses and commercial buildings. This is often referred to as “embodied energy.” A truly thorough examination of energy use by the building sector would include that portion of industrial energy use for making concrete, window glass, steel I-beams, plywood, and the other building products. I would guess that that is easily a quad or two, though I have not attempted to include that information here.
Transportation energy use related to the built environment
With the transportation sector, the impact of buildings — and where we put them — is a lot more significant. Development patterns have a huge impact on the energy expended for transportation. From the 423-page Transportation Energy Data Book – Edition 31, published by Oak Ridge National Laboratory in July 2012, we find that cars and light trucks accounted for 58.7% of transportation energy consumption in 2010, while medium and heavy-duty trucks accounted for 22.3%, buses 0.7%, air travel 7.8%, ships 5.0%, rail 2.1%, and pipelines 3.4% (Table 2.6).
We further find that for household travel, in 2009, commuting to work accounted for 28.7% of vehicle miles traveled, shopping 15.5%, other family/personal business 15.7%, vacation 2.3%, visiting friends and relatives 9.4%, and other social/recreational 13.5% (Table 8.9).
In Table 8.17 we find that in low-density areas (less than 1,000 residents per square mile) significantly more miles are driven per vehicle per day: 31.6 miles, vs. 18.5 miles when the housing density increases to 10,000 to 25,000 residents per square mile and 14.8 miles with densities above 25,000 per square mile.
The bottom line
What I read into these numbers is that where we build our homes and where companies build their offices and factories has a huge impact on the amount of energy we use in transportation. (I wrote about this in a September 2007 article in Environmental Building News, “Driving to Green Buildings,” suggesting that we consider a new metric of “transportation energy intensity.”)
I would venture to say that a third of all of our transportation energy use relates to building location. We shouldn’t ignore this energy when we’re focusing on the energy use of buildings.
A third of our transportation energy use amounts to 9.0 quads. If we lump that into the expanded column of buildings and the built environment in our initial total of 21.6 quads for residential buildings and 18.0 quads for commercial buildings, and include the 0.9 quads of industrial energy use having to do with heating and illuminating factories, that would mean that buildings and the built environment account for 49.5 quads of primary energy consumption, or 51% or total energy use.
In other words, the direct operation of buildings for heating, cooling, lighting, and appliances, along with a reasonable share of energy use associated with getting to and from those buildings, accounts for over half of our energy use — significantly more than the 41% figure that’s commonly quoted.
This means that those of us involved in influencing how buildings are designed and built and where we build — and that includes building owners — share even more responsibility for the nation’s energy consumption (and greenhouse gas emissions) than is commonly suggested. We have a lot of work to do!
I’d love your thoughts on whether this argument makes sense.
Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.