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Epidemic of Obesity?
Jerry Yudelson, PE, LEED® AP
Monday, October 30, 2006
According to numerous studies and reports over the past few years, the United States is suffering through an "epidemic of obesity," with the average American ten pounds heavier than before and the number of "super-sized" people growing rapidly. Many health complications abound, including diabetes, heart disease and premature death. Airlines are burning more fuel, to compensate for another 1000 to 2000 pounds on each flight.
Other studies link this epidemic to our approach to urban design, namely the tendency to drive more and walk less, because of the spread-out nature of work, home, shopping, recreation, etc. (This tendency was satirized beautifully by Steve Martin in the 1980s movie, L.A. Stories: at the opening of the movie, he walks out of his house in the morning, gets in his car, drives to the next house and gets out of the car to visit his neighbor.)
I’ve found this out first-hand: since moving to the outskirts of Tucson, Arizona, in April, I’ve been both driving more and walking less than when I lived in downtown Portland, Oregon. Tucson is a very spread-out town, with little public transportation, very unlike Portland, which is quite compact with excellent public transportation. Every errand requires a car, and the major roads are all a mile apart. So, every errand requires at least a two-mile drive, and most require a six-mile roundtrip. (There are some bicycle commuters; I have a friend who rides 12 to 15 miles a day, to and from work, but this is pretty rare; most bicycling in Tucson is recreational, unlike Portland, which has considerable bicycle commuting.)
Since this is a green building web site, I’ve wondered what implications this epidemic of obesity might have for building design, particularly its impact on energy-efficiency and indoor air quality. We already know that many people in our buildings are "too hot, too cold," and that heavier people tend to be hotter (not universal, I know) than thin people.
From a design perspective, one of the best ways to reduce energy use in many buildings is to use natural (vs. forced) ventilation and to install operable windows. Typically, in naturally ventilated buildings, the acceptable temperature in workspaces is allowed to fluctuate over a wider range, typically both 3 to 4 degrees Fahrenheit hotter and cooler, than the normally tight 73F to 74F +/- 2F. On summer afternoons, many naturally ventilated buildings will have work spaces that exceed 78F or 80F, for perhaps 80 to 100 hours per year (about 3 percent to 5percent of 2000 total annual work-hours).
This slight discomfort yields a significant savings in both energy use for cooling and a first-cost advantage of a reduced size for the HVAC system. However, what about the people in the space? Are we designing comfort systems for them as they should be, or as they really are? If they’re really uncomfortable, what happens to their expected productivity gains, one of the major business case arguments for green buildings? (People cost $200 to $600 per square foot, vs. $1 to $3 for energy, so a 1 percent productivity gain pays for all the energy use, and a 1percent productivity loss doubles the energy use!). Is it a false economy to sacrifice their comfort in the name of energy efficiency?
Now, we know that public employees constitute about one-third of the workforce. Are we opening ourselves up for grievances and impromptu walk-outs in green buildings when we fail to deliver expected comfort levels? It does little good to appeal to the example of Europeans and others, who are perfectly willing to endure a little hotter temperatures in the summer (and dress lighter) and cooler temperatures in the winter (wearing the famous Jimmy Carter cardigans to work), when our workforce is quintessentially American.
Here are some solutions:
Underfloor air distribution (UFAD) systems
, in which each work station is able to adjust individual comfort levels (temperature and air flow) by manipulating in-floor air diffusers. This solution works very well for open-plan offices with large floorplates. It saves a considerable amount of energy, since air is typically supplied at 62F instead of 55F from a conventional overhead air diffuser, requiring less cooling. Because wire and data cabling also comes up from below the floor in these systems, moving workspaces (which most companies do at the rate of 20 percent per year or higher) is typically fast and cheap, leading to cost recovery in less than three years in most cases because of significantly reduced “churn” costs. These systems enjoy widespread use in Europe but are just beginning the adoption cycle in the U.S. The primary drawback is a first-cost increase of typically (net) $4 to $6 per square foot, a penalty that is often offset by the ability to buy cheaper furniture systems that don’t need electrical hook-ups.
Thermal energy storage
, where we still supply the same cooling energy but use far cheaper “off-peak” electricity to make chilled water or ice during the evening and night, store it, and deliver it during the warmer afternoons. With peak power rates climbing above $0.20 per kilowatt-hour in many metropolitan areas, this solution makes sense for many new buildings. Thermal energy storage is a viable option for any new building and typically pays for itself by allowing the designers to decrease the size of the HVAC systems for summer cooling.
Talk to the people!
If there’s one thing architects and buildings owners and facility managers are loath to do, it’s to involve the actual users of a building into the design process, so that they understand what is being done to save energy, what the implications are for thermal comfort and how to explain it to their co-workers. I have actually been involved with projects where the project team was forbidden by the facilities department (under pain of excommunication or something similar) to talk with the actual users of a new building, because in their view, it would slow down the design process and because facilities staff said, "we’ve already had all the discussions we need to with those people." Without good user education about the reasons for natural ventilation, can you blame people if they get upset if the building is too hot or too cold?
Design with Climate.
I’m just amazed at how many buildings I see in the desert Southwest with no shading on the south and west (or east) façades, either recessed windows, overhangs or wing walls, thereby guaranteeing hot spots that won’t allow HVAC systems to be downsized to save energy. In most cases, it’s just a style that architects have adopted for buildings everywhere with little thought to local climate dynamics. In the Southwest, buildings should be like caves, with thermal mass (concrete) to reduce temperature fluctuations and lots of shading on the solar-exposed façades (think of the Mesa Verde National Park cliff dwellings in Colorado).
Health clubs in every office building?
Perhaps the best solution is to make it easy and convenient for our friends and colleagues to exercise right in the building, as a way to lose weight effectively. Then building design might be a little less challenging, and natural ventilation/operable window design approaches a little more popular. This would add slightly to the cost of building operations, but could more than pay for itself with reduced health-care costs.
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