Energy: doing more with less

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Doing More With Less Part 2: Case Study Sagas and Real Numbers
1.31.06 David Regen Jr., Marketing Director, Energy Systems, Inc.


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Case Study #3 : The Spence Office Building
In 1979, Harold Reeves and a group of investors were planning the design of a 20,008 square foot multi-tenant, two story office building in Nashville, Tennessee. This was to be ESI's first “landmark” all new commercial construction project. Mr. Reeves had previously owned office buildings and was sensitive to potential exposure to the high utility costs associated with them. To maintain a high degree of flexibility, the owners wanted to lease office space with utilities included.
Mr. Reeves had learned of ESI's performance in homes and asked if similar performance could be provided in his new commercial office building. ESI responded with a proposal to design and build a thermal envelope and HVAC system for the building that would be guaranteed not to use more than the equivalent of 64,300 kwh per year. The original heating system was natural gas.
For each of the two years of the warranty, the annual measured energy use was almost 7% under the warranted amount. Since then, the building's performance has continued at a level that qualifies it as Energy Star Certifiable, based on 1994 building energy use data. This commercial building could not be rated in its early years because it was built about 15 years before the start of the Energy Star benchmarking database.
Several interesting things have happened in the life of the building relating to the gas heating system, which consisted of a 120,000 Btu per hour gas furnace. Now imagine a world, where the same size furnace which now operates a typical 2000 square-foot home suffices in a 20,008 square-foot office building. That's an order of magnitude improvement! Some might find the “sounds too good to be true” demon to be a little distracting, but we may have to imagine this world sooner than later. We may not have a choice!
This prototype office building from the early 80's only needed 15,250 cubic feet of natural gas during the entire first winter heating cycle. At the prevailing gas prices of the time, this cost the property owners, Mr. Reeves and his investors, a total of $52.58. If 2004 gas rates had been in place back in 1981, then their operating cost for gas heat would have been about $150 for the year. With a projected 70% increase, the gas bill would result in a whopping $255 for the year! I wonder how many property owner's of a 20,000 square foot commercial building in a 3800-degree-day heating climate would like to have to pay for this kind of gas bill.
That's the beginning of the story of what Mr. Southerlan jokingly refers to as “the first and worst” office building. On March 5, 1981, the Nashville Gas Company sent a technician to change out the meter, suspecting it was broken. Sound familiar? Mr. Southerlan just happened to be there when the technician arrived. He asked for a measurement of the furnace's firing rate furnace on the old meter. The firing rate turned out to be 73,440 Btu per hour, rather than the furnace's rating of 120,000 Btu per hour.
That's when Mr. Southerlan got the uneasy feeling that his energy claims might be based on faulty data. So while the technician was changing the meter, he ran some numbers. What difference would it make anyway? An $85.78 per year heating bill for a 20,000 square foot office building, isn't much more believable than $52.58.
After the meter was changed, he asked the technician to check the firing rate again. This time the tech measured a firing rate of 56,492 Btu's per hour with the same furnace. Now it's getting more confusing rather than less. This finding says the old meter was 30% faster than the new meter, but still nowhere near the specified firing rate of the furnace. This furnace had a two stage gas valve. The valve was designed to fire the furnace at about half capacity on start up, and after a few seconds, it was supposed to open to full fire. It was later found that the valve was defective and would not advance to full fire.
Mr. Southerlan states, “ I had asked that the old meter be checked for accuracy and some time later, it was reported to me that the meter was accurate to within 2%. Before I got the report, I had called the gas company and explained how the old meter measured at a higher rate than the new meter.” They actually sent Mr. Reeves a refund! The defective valve in the gas furnace wasn't changed for another four years, but there was never any indication that the furnace firing at half capacity was incapable of heating the building. After another three years, the gas company thought it might be time to change the meter again! But wait, there's still more to the story.
In 1990, it was noticed that the gas “service cost” had risen to $11 per month. Southerlan suggested to Mr. Reeves that if he had the gas company turn off the gas each February 15 and back on each December 15 starting in 1991, he would save $110 minus the $35 “turn on fee” for a net savings of $75. He did this, except for one thing. Even though he was there everyday, it never occurred to him to call them back to turn the gas on.
Apparently, it never got cold enough in his building for him to notice and some time in 1995 the gas meter disappeared for good. His building has been able to maintain an acceptable space conditioned climate without using its gas heating system since 1991. Mr. Reeves has found out that if a very low wintertime temperature occurs over a weekend or holiday (usually once a year), if he turned on all the lights on his usual arrival time of 6:00 am, the building is at normal temperature by 8:30 am.
Since the office building went on line, August 26, 1980, the cooling system has come on for some part of almost everyday of normal occupancy. Having to cool your building in the wintertime may not be a bad problem to have. And all this from a building that cost only $33 per square foot to build in 1979.
In 1984, the Tennessee Valley Authority investigated the performance claims related to the Spence Office Building. The following summary of that analysis leads to some very significant conclusions. The analysis compares the annual energy use of the building's HVAC system to that of thirteen other comparable office buildings. As none of the thirteen buildings had meters on their HVAC systems, computer calculations were used for the comparison. Remember, this is a comparison between the energy use of the HVAC systems, not total building energy use. The average annual use for the thirteen office buildings was 64,347 Btu per square foot. For the Spence Office Building, it was 16,812 per square foot, about one fourth of the thirteen others.
The measured HVAC system annual energy use for the Spence Office Building during the analysis period was 11,885 Btu per square foot. This is 30% less than what was predicted by calculation. A similar discrepancy has also been observed when comparing the performance of the Synergy System with contemporary computer modeling programs. According to industry contacts, finding a building having lower energy use than the projections offered by computer modeling is a rarity. This is one more piece of evidence that suggests the building industry has much to learn about the synergistic effects of energy-use components in buildings.
What does this mean in terms of dollars? In 1983, in Nashville, Tennessee, the difference in cost between 64,347 and 16,812 Btu per foot per year was $.7667 per square foot per year. For the Spence Office Building, at 20,008 square feet, this amounts to $15,340 per year. Ignoring the fact that utility rates have gone up since 1980, to this date, Mr. Reeves has avoided at least $383,500 in utility costs. This is about 60% of the initial cost of the building.
Let's not forget environmental impact. The generation of one kwh of electrical energy by coal fired plants results in the emission of about 2.06 pounds of pollutants. The difference per year between 64,347 and 16,812 Btu per square foot equates to 19.93 kwh per square foot. For the Spence Office Building, this amounts to 278,680 kwh of on-site energy use avoidance. Neglecting transmission and distribution losses, this amounts to over 574,000 pounds or 287 tons of atmospheric pollution avoided per year. So far, this adds up to over 7100 tons of air pollution avoided since this one building came on line.
The consistent question has been this: How much more did the building cost to get this kind of performance and what was the payback? According to Mr. Reeves, the building's cost for a Synergy System was $24,050 less than other bids for a conventional HVAC system, which did not include thermal envelope costs.
When the size of a building exceeds 15,000 square feet, a Synergy System usually costs less than the conventional approach. For buildings below the economy of scale threshold (in the 10,000 square foot range), the initial cost of a Synergy System may be higher, but the payback is still less than 3 years, which at this time still beats any investment in a renewable energy technology.
If saving our precious energy resources, gaining some self sufficiency, possibly averting an apocalypse, and preserving our environment for our children and grandchildren were not enough, there is always the importance of the load factor. Critical to not operating our power infrastructure in the narrowest of margins is how the load factors of buildings interact with what the power company does.