Skyscrapers, houses, and energy consumption


While perusing another blog yesterday, I encountered a link to a New York Times article describing the Green™ aspects of skyscrapers. [1] Sorry to burst anybody’s bubble, but people in the building industry have known such things for decades – or, at the very least, they have known the principles that make such conclusions unsurprising. A little mental correlation can flesh out the rest of the situation, so here are some of the reasons behind the conclusions presented in the article.

First and foremost, we need to be absolutely clear about one issue that seems to have escaped popular understanding: energy. By energy, I do not just mean sources of energy, such as the fossil fuels and Green™ energy sources that are much in the news of late; energy consumption must also be considered, and it is in this regard that much of the public appears to remain ignorant. Cars and our oil-heavy culture are often bemoaned in environmental circles, but oil itself accounts for only a fraction of our energy consumption. Everything we do and every product we buy requires the consumption of energy, and it is in this regard that living within cities, and particularly in skyscrapers, can be far less energy intensive than suburban living.

One major source of energy consumption in any living space is climate control, either in heating or cooling a space, depending on the season. Obviously, one can mitigate these costs (somewhat) by maintaining temperatures that are outside of typical comfort zones, e.g. I usually keep the thermostat set for 60 degrees in the winter (summer is a different story, however; I hate heat). An unavoidable factor in climate control for detached houses, however, is that they are surrounded on all sides by surfaces that are exposed to the outside environment. Even when insulated, these walls gain heat in the summertime and lose heat in wintertime; the insulation used in these walls is very much a compromise of thermal efficiencies: too little insulation, and the house is an icebox in the winter; too much, and it becomes an oven in the summer. The insulation, therefore, cannot be too resistant to heat transfer. Apartment units in a high-rise (or even in midrises, for that matter) are much more efficient in this regard, as they often have, at most, two faces exposed to the outside, and sometimes only a single exposed surface. Similarly, townhouses, by virtue of sharing two walls with adjacent units, are also much more efficient when it comes to internal climate control. Since the temperature variation from one apartment unit to another tends to be far less than it is to the outdoors, the heat loss or gain between units is, consequently, far less across these shared surfaces than it is for the exposed surfaces. [2]

Another factor that affects the internal climate of a house or apartment is the size of the space itself. Obviously, the larger the space, the more energy required to maintain a given internal temperature. A typical two bedroom apartment, for example, usually encompasses an average of about 1,100 square feet; such an apartment would be well-suited to be the first residence for a young family with no children. A typical suburban detached house may be double, or even triple, this size, and, as a result, requires proportionately greater amounts of energy to maintain its internal environment. [3] No matter how thermally efficient the house itself may be, its size alone means that the climate maintenance systems must manage a larger volume of air. Consequently, it a greater amount of energy will be needed to heat and cool the space.

Size is also a factor in the amount of electricity consumed by a house, compared to that consumed by an apartment. Larger rooms require more lights to illuminate, while smaller rooms need less light sources to maintain the same level of illumination. Consider, for example, that the largest overall size of any room in an apartment tends to be roughly 150 square feet (equivalent to a 12′ x 12′ room, which is 144 sq. ft.); such a room can be brightly illuminated by as few as two or three light bulbs. [4] By contrast, it is not uncommon for a house-scale living room to be twice as large as this figure, with a corresponding increase in the number of light fixtures required to maintain a useable level of illunination. Add up the differences from all the rooms in the house versus the rooms in an aparment, and the additional energy consumption can become substantial. Of course, not all of the rooms will be lit at any given time, but regardless, larger rooms need more energy to illuminate, so these differences will always be present.

Less obvious sources of energy consumption are the things we use to fill our respective domiciles. Keep in mind that there is practically no way to divorce oneself from our energy economy; people who claim to live “off the grid” are probably not succeeding at this quite as much as they would like to believe. The reason for this is that every product we buy and use, from food, to furniture, to electronic devices, etc., are almost all produced on assembly lines these days (or, at the very least, in factories, and these consume energy, even if they are not running mechanized assembly lines), and must be transported to wherever they are finally sold. Once sold, they must be again transported to our homes. Humans generally have something of a “nesting” instinct; we really do not like bare rooms, and have a tendancy to fill them with things. Houses, being much larger than apartments, will inevitably be filled with more things, whatever they happen to be. Additionally, given the alarming frequency with which people tend to replace the things they buy with “improved” versions, each subsequent revision cycle for a house will contribute that much more to energy consumption than a comparable apartment would require. Again, to some degree, this may be mitigated by not buying as much stuff, but as I’ve previously mentioned, societal attitudes tend to be particularly resistant to change, and I presume that this is no exception.

Herein is one of the most pervasive aspects of our modern energy economy. As the article points out, one of the idyllic visions of environmentally harmonious living is Thoroeau’s experiences as depicted in Walden; no matter how faithfully one replicates his experiment, it would be far more difficult to wholly extricate oneself from our modern energy economy than the idealists might want to believe. Consider what would be involved in moving out to the wilderness: how do you get there? Did you drive or hitch a ride? These both consume energy in the form of gasoline; better to walk, though this means you will be unable to carry a substantial load of equipment. Speaking of equipment, what tools do you need, and where do you get them? If you bought them in a store, again, this consumes energy, and probably more than you might suspect. [5] How about the seeds you’ll need to grow crops? The bags used to transport the supplies? The clothes on your back, the shoes on your feet? What happens when you need to replace any of these items? Do you buy more, or do you make your own. If the latter, where do you get the raw materials, and how do you make them suitable for use? What about your crops? Obviously, it would be easier if you used modern fertilizers, but one can do without. But what about irrigation? Could you build a machine that can move sufficient quantities of water without requiring a pesky thing like an engine? Perhaps, if such individuals modelled their efforts after the traditional practices of pre-Columbian Native americans, they could truly extricate themselves from the “grid,” but I suspect that very few individuals have the discipline and fortitude to do this.

All of these considerations vastly complicate any efforts to transition our national energy economy from fossil fuel sources to alternative Green™ sources in any short amount of time. Additionally, since most of these latter sources are not currently deployed in any substantial fashion (with the exception of the still-anathema nuclear power), the costs required for implementing these systems would have substantial ramifications throughout our economy. The relatively low product prices we currently enjoy are contingent on access to cheap, widely available energy sources, and in the absence of such sources, prices for each step from production to consumption will necessarily increase, possibly in a spectacularly dramatic fashion. I do not point this out with the intention of discouraging investment in alternative energy sources; regardless of the ultimate costs involved, we will eventually be required to pay them, as fossil fuels are known to be finite resources. I merely point out that we cannot rush headlong into any solution, simply because it is ideologically attractive (as many of the more fanciful Green™ technologies are); we must be wary of just how complex our energy economy really is, and we cannot afford to be naïve about the extent to which our commodities economy is inextricably tied to our energy economy. We also cannot afford to make too many mistakes when selecting technologies to implement, as we have only a few precious chances to make the right choices, before the increasing scarcity of fossil fuel sources drives up their costs beyond that which our economy (either one) can tolerate without suffering damage. This, more than anything else, demands that we proceed with all due caution, particularly in light of the recent damage our economy has already suffered.


[1]: New York Times article, 10 March 2009.

[2]: In fact, most shared (party) walls between units are also insulated, but this has less to do with thermal performance than acoustical performance. The insulation used in this application is selected for its sound isolating qualities, rather than its thermal performance. While it will have some effect on the thermal gain or loss through these walls, since the temperature variations are so slight, it generally does not factor much into the thermal characteristics of each apartment.

[3]: To be fair, HVAC systems in houses are often split into zones that can have different temperature settings; typically, this is accomplished by using separate furnace/compressor units for each zone. Typically, these zones are set up with one per floor; more sophisticated systems can split up zones within a single floor, but these systems are usually more expensive and, therefore, not frequently used.

[4]: The living room in my current apartment is somewhat less than 150 sq. ft., and while we have it brightly lit with three bulbs on the ceiling fan, I suspect that it would still be adequetely lit with just two bulbs. And yes, before you ask, my roommate and I splurged on CFL bulbs, so there.

[5]: Consider how much energy is required to locate and procure the raw materials that go into making each tool; the energy required to transport those raw materials to a processing facility; the energy required for refining those raw materials into useable compounds; additional energy for transporting the refined compounds to a production facility; the energy required to convert these refined materials into a finished product; more energy for transporting the finished product to market (potentially via indirect methods, such as sending it from the factory to a wholesaler, and then to the retailer); and finally, the energy required to transport the finished product to its final destination. All that energy needs to come from somewhere.


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