Wm. G. Sampson, General Manager of the Indianapolis-Marion County Building Authority, released the results of a recently completed report which evaluated the savings on air conditioning costs for this past summer after having MicroLouvre (f.k.a. Koolshade) Solar Sun Screens installed on the Indianapolis City-County Building. The following are excerpts from that report
The Indianapolis City-County Building consists of a center tower of twenty-eight (28) stories and two (2) wings equal to seven (7) stories each. The total complex has close to one million gross square feet of space.
The building is constructed as a curtain wall structure with 3,420 windows. It is heated with city steam and cooled by 1,000, 1,350, and 1,500 ton Centravac refrigeration units through dual duct high pressure fan systems.
The building’s utility costs were a problem before the “energy crunch” hit, but after the energy crunch, the costs became critical.
Ron Reinking, Assistant General Manager, and I embarked on a cost cuffing program that took all phases of the operating costs into account We considered several choices available.
We researched the market for various films, sun screens and sun shading devices to reduce solar radiation entering through the glass.
We first tried a vinyl covered fiberglass exterior screen which we quickly rejected because of poor visibility. In addition, we were concerned with the life span of such a product when subjected to high winds and icing conditions.
We next selected MicroLouvre exterior solar screens because they have been on the market since 1939 and time tested for durability. The screens, machine-woven of small bronze louvers, permit good visibility and have withstood high winds and icing conditions. They have proven to be effective in reducing solar loads on buildings in the United States and Europe.
life of the film under normal window washing conditions is five to six years. However, MicroLouvre sun screens have a proven life expectancy of approximately five times that of the films. We were convinced MicroLouvre was the most efficient product for our purpose.
RESULTS = SAVINGS
Solar energy readings were listed at fifteen (15) minute intervals for each day during the periods June 8, 1977 through October 7, 1977, and June 8, 1978 through October 5, 1978. The readings indicated an 11.6% increase in solar radiation for the four-month period in 1978 over the four-month period in 1977. This is precisely the data 1 needed to accurately evaluate the effectiveness of our MicroLouvre Sun Screens.
During the four month period in 1978, the electrical consumption of our three (3) chillers was down 11.8% from the four month total for 1977. This reduction becomes much more impressive when the increased solar radiation readings are considered. The combined evaluation of these measurements shows that for the 1978 test period, the chiller electrical consumption per unit of solar energy recorded was 21.0% less than that used during the same period in 1977.
This test period was selected because these months constitute the majority of the cooling season and the time for maximum chiller electrical consumption. There is, however, valuable information to be found by studying the cooling season months which have more moderate temperatures. For the months of April, May, October and November, the chiller electrical consumption during 1978 was 50.6% less
We then selected a quality, well known, highly reflective film for a test on the inside of a window. We wanted to compare the film’s effectiveness against MicroLouvre because the product is less expensive.
We constructed two, one foot (1 ft.) square boxes from one inch fiberglass having a density of 11.25 lbs. per cubic foot. The boxes were open on one side only. All corners were sealed with the open side sealed to the inside surface of a one inch insulated glass window.
All windows are one inch insulated with a gray polished plate glass on the outside. Each box was located exactly in the same position of each glass. A thermocouple was inserted in the exact center of each box. Thermocouples were interchanged to check for accuracy. Each thermocouple was an integral part of a forty-eight (48) hour chart recorder with time slots to accurately make time comparisons.
We tested the film against existing glass for the first test (Fig. A). This showed a 10° F difference in heat buildup within the boxes. The next test plotted the film against MicroLouvre Screens (Fig. B). We noted a 26° F difference between the film and MicroLouvre Screens. After three different comparative tests, each demonstrated approximately 26° F difference.
During these months, the sun screens allow us to maintain temperature in the building without running a chiller on days which would require the running of a chiller if the solar heat was allowed to enter the building.
Considering both the maximum and moderate load periods, the chiller electrical consumption alone for calendar year 1978 was 22.3% less than for calendar year 1977. This reduction was achieved during a year in which the majority of the cooling season had a substantial increase in solar radiation over the previous year.
Also, reduced refrigeration load means reduced condenser water make-up and chemical treatment requirements. Our records show an 18% reduction in chemical treatment costs during the 1978 cooling season compared to the 1977 cooling season.
Less obvious savings such as reduced wear on operating equipment, reduced window cleaning expenditures and reduced heat loss through glass in winter are additional benefits resulting from MicroLouvre.
With the cost of energy rising as it has in the past few years, the reduction in power use for air conditioning, the reduced equipment use and the savings in man hours, we expect to amortize the cost of the MicroLouvre Solar Screens conservatively in seven to eight years. However, with any unexpected energy cost increases this time would be reduced. We think this is a good investment for the Indianapolis City County Budding.