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15 <br />dayss12. The combined demand for heating and cooling in FY 10 was 10% <br />greater than the demand in FY 09 due to temperature differences between the <br />two years. <br />Figure 3: Total HDD and CDD Per Fiscal Year <br />5, 000 <br />u <br />D 4,000 <br />U <br />a <br />m 3,000 <br />O <br />= 2,000 <br />1,000 <br />4,668 4,761 4,869 q,g~ <br />4 816 5 327 <br /> <br /> <br /> <br /> <br /> 3,165 3,~gp 3,310 3,954 3,123 3,518 <br /> <br />FY 05 f-Y O6 FY 07 FY 08 FY 09 Fl' 10 <br />Fscal Year <br />s HDD <br />CDD <br />In order to remove weather as a factor when comparing energy use from one <br />year to the next, a process referred to as "weather normalization" is undertaken. <br />The first step in weather normalization is to determine how much of a building's <br />energy use is attributable to variations in weather conditions, specifically <br />temperature. Once this has been determined, the amount of energy a building <br />would use based on any set of weather conditions can be calculated. In other <br />words, it can be shown how much energy a building would have used in FY 05 if <br />it had experienced the weather conditions that occurred in FY 10. Figure 4 <br />presents projected energy use that would have been used at County facilities in <br />FY 10, based on their FY 05 energy performance. By using weather <br />normalization, the difference in weather can be removed as a possible <br />explanation for why a building used more or less energy in one period compared <br />to another period, leaving only human behavior or building modifications to <br />explain changes in energy use in a building. Such changes could include <br />increased or decreased staffing levels or the installation of more efficient lighting. <br />Since normalization requires at least one to two years of good quality data, most <br />new County buildings, comprising approximately 240,000 sq. ft - or .about half of <br />the total County occu-pied space, cannot yet show weather normalized usage. In <br />cases where projected figures can-'t be used for new buildings, projected usage is <br />calculated using actual usage figures. <br />As seen in Figure 4, total County energy use as measured in MMBTU/1000 sq. <br />ft., when compared to weather normalized figures for FY 05 energy use, shows a <br />0.8% decrease. <br />92 Heating degree day (HDD) is a measurement designed to reflect the demand for energy needed to heat a home or <br />business. It is derived from measurements of outside air temperature. The heating requirements for a given structure at a <br />specific location are considered to be directly proportional to the number of HDD at that location. A similar measurement, <br />cooling degree day' (CDD), reflects the amount of energy used to cool a home or business. A further explanation of the <br />terms CDD and HDD can be found in the definitions section of the report. <br />12 <br />