Southern York County Library

Transcription

1 Southern York County Library Measurement & Verification Report April 20, 2009 Provided by: York County Community Foundation Energy Program Prepared by: Energy Opportunities, Inc East Camping Area Road Wellsville, PA 17365

2 Table of Contents Introduction... 1 Executive Summary... 1 General M&V Approach... 2 Energy Efficiency Measures (EEMs)... 2 M&V Period... 3 Data Collection... 3 Data Analysis... 3 Heating... 3 Cooling... 3 Fans... 5 Interior Lighting... 5 Exterior Lighting... 5 Domestic Hot Water... 5 Electrical Equipment... 5 Energy Model Calibration... 7 Actual Weather Data... 7 Occupancy Schedules... 8 HVAC Equipment and Schedules... 9 Interior Lighting Exterior Lighting Domestic Hot Water Electrical Equipment Utility Rates Comparison and Error Analysis Development of Calibrated Baseline Building Conclusions Energy Cost Saving Opportunities to Consider... 24

3 Figures Figure 1: Linear Regression of Monthly Cooling Degree Days and Energy Use... 4 Figure 2: Annual Energy Consumptions by End Use in MBtu... 7 Figure 3: Office Daily Temperature Profile (Heating)... 9 Figure 4: Estimated vs. Modeled Monthly Cooling Energy Figure 5: Percentage of Time Lights on Each Hour by Space Figure 6: Actual vs. Modeled Lighting Schedule Figure 7: Modeled Hourly Electrical Equipment Demand Profile Figure 8: Monthly Total Electricity Comparison for M&V Period Figure 9: Revised Annual Energy Consumption by End Use (MBtu) Figure 10: Monthly Total Electricity Comparison for M&V Period Figure 11: Energy Summary by End Use Graph of Original Models (Proposed and Budget Buildings) and Calibrated Models (As Built and Baseline) Tables Table 1: Annual Energy Use and Cost Comparison... 2 Table 2: Monthly Cooling Degree Days and Energy Use (Estimated Values in Red)... 4 Table 3: Annual Electrical Equipment Estimate... 6 Table 4: Occupancy Schedule... 8 Table 5: Thermostat Temperature Settings... 9 Table 6: As Built and As Modeled HVAC Equipment Table 7: Water Heater Run Time and Demand Summary Table 8: Energy Cost Summary Table 9: Total Annual Energy Consumption Comparison by End Use (MBtu) Table 10: Total Annual Energy Consumption Comparison by End Use (kbtu/ft 2) Table 11: Estimated Cost of Unit Heater Operation Table 12: Total Annual Energy Consumption Comparison by End Use (MBtu) Table 13: Total Annual Energy Consumption Comparison by End Use (kbtu/ft 2 ) Table 14: Energy Summary by End Use of Original Models (Proposed and Budget Buildings) and Calibrated Models (As Built and Baseline) Table 15: Energy and Cost Summary by Fuel Type of Original Models Table 16: Energy Cost Summary by Fuel Type of Calibrated Models Table 17: Additional Temperature Setback/Setup Savings Estimate... 25

4 Introduction This document describes the measurement and verification (M&V) completed for the Southern York County Library. The Southern York County Library has achieved LEED Certification under the LEED NC v2.1 Rating System. The project is located in Shrewsbury Borough, York County, PA and consists of a one story building totaling 10,096 ft 2. The structure is conditioned by (5) split system DX air conditioners with high efficiency propane furnaces. The lighting system consists of ceiling recessed and surface mount fluorescent fixtures with T8 lamps. This report outlines the approach taken to determine actual energy savings resulting from a series of interactive measures taken to reduce energy consumption compared to a baseline building. The energy savings were estimated using a computer simulation of the building s energy performance, and verified through measurement of the as built library s energy consumption. The energy model was created using ENERGY 10, a program developed under the leadership of the National Renewable Energy Laboratory and produced with funds made available by the United States Department of Energy. The energy modeling and M&V were completed by Energy Opportunities under funding from the York County Community Foundation s Energy Program. The Energy Program provides technical, financial and educational assistance for a wide range of non profit organizations in York County. Commissioning of the library was completed by 7group, LLC. Executive Summary The purpose of the M&V for the Southern York County Library was to determine the actual energy savings generated by the project. The amount of energy savings is relative to a similar building which is minimally compliant with ASHRAE Standard The energy model of the asdesigned building predicted an energy cost savings of 34.5% relative to the ASHRAE baseline building. After calibrating this original energy model based on the measured operating characteristics of the as built building, an actual energy cost savings of 42.0% were determined relative to a similarly calibrated baseline building. Since the actual level of savings was within 10% of the predicted savings, the savings were assumed to be verified. The actual building is using 36.1% less energy than the proposed building energy model, and its energy cost is 25.4%, or $2,911, lower than predicted. Although the Southern York County Library has exceeded the expectations for energy performance, the M&V analysis has revealed the potential for significant additional improvement. The following table summarizes the annual energy consumptions of the original proposed energy model, the calibrated energy model, and the actual building during the M&V period. 1 Southern York County Library M&V Report

5 Table 1: Annual Energy Use and Cost Comparison P roposed Model Calibrated Model As Built Library Electricity (kwh) 101,670 57,067 57,164 Electricity Cost (&) $ 11,456 $6,015 $6, Propane (therms) 2,216 1,683 1,433.2 Propane Cost ($) $2,020 $2,959 $2, Total Energy (MBtu) Total Cost ($) $11,456 $8,974 $8, Energy Use Intensity (kbtu/ft 2) Energy Cost Intensity ($/ft 2 ) $1.13 $0.89 $0.85 General M&V Approach The M&V Plan was designed to comply with the provisions of the International Performance Measurement and Verification Protocol (IPMVP) and LEED NC v2.1 EA Credit 5 Measurement & Verification. The plan followed IPMVP Concepts and Options for Determining Energy Savings in New Construction, Volume III, April 2003, Option D: Whole Building Calibrated Simulation, Method 2 and Method NC C 01 in M&V Guidelines: Measurement and Verification for Federal Energy Projects, V2.2. Data was collected during a year long period following building construction using a variety of measurement methods and equipment. This data was then used to estimate the annual energy consumptions of the various end uses in the building, as well as the building s operational parameters. After reconciling these estimates with the annual energy consumptions from the utility bills, the energy model was calibrated based on the gathered data. Energy Efficiency Measures (EEMs) The following EEMs were included in the as built library, and their installation and proper operation were verified as part of the building commissioning completed by 7group. Energy Efficiency Measures Increased Roof and Wall Insulation Slab Edge Insulation High Efficiency Windows Reduced Interior Lighting Minimize Exterior Lighting High Efficiency DX Air Conditioners High Efficiency Propane Furnaces 2 Southern York County Library M&V Report

6 M&V Period The M&V process began in April 2006, with the installation of monitoring equipment within the building. The data collection concluded in April 2007, and the data was organized for calibration of the building energy simulation. The simulation calibration and savings verification was completed in February, Data Collection A variety of measurement and monitoring methods were employed to collect data on the actual energy consumptions of the building s systems. Clamp on ammeters were used to take spot measurements of the compressor and fan motors, as well as individual lighting fixtures. Plug in kwh meters were used to measure electric usage for a variety of receptacle equipment. These include the refrigerator, copiers, printer, and representative samples of office and public computers. HOBO dataloggers were used to record and trend temperatures, humidity, interior lighting levels, water heater run time, fan run time, and condenser energy use. Occupancy and schedule information was obtained from discussions with staff along with monthly attendance records. Monthly electric use was obtained from Metropolitan Edison utility billing data, and propane deliveries were obtained from Holiday Gas. Historical hourly weather data for York, PA during the M&V period was obtained from Weather Underground. Data Analysis Proper energy model calibration requires an energy consumption comparison at the end use level rather than the whole building level. The first step in this comparison was to use the collected data to determine the energy consumptions of each end use during the M&V period. Heating The energy use for heating during the M&V period was estimated from the propane deliveries, since the propane is used for heating purposes only. However, the deliveries only occur a few times throughout the year and did not coincide directly with the M&V period, so an average over a fouryear period was used to estimate the annual heating energy consumption. For these reasons, the heating energy estimate cannot be made on a monthly basis, and does not coincide with the actual weather conditions of the M&V period. The delivery units (gallons) were converted to energy units (kbtu) using a heating value of 91,500 Btu per gallon of propane. The result was MBtu, or 14.2 kbtu/ft 2 of heating energy consumption per year. Cooling The energy use for cooling during the M&V period was estimated from the amperage data logged for representative condensers during two separate metering periods. The amperage for each 3 Southern York County Library M&V Report

7 representative unit was logged in 5 minute intervals during the months of April, May, June, August, and September. The logged amperages along with the voltage of each unit were used to estimate the kwh used during each 5 minute interval, and summed to obtain the monthly kwh per unit. Estimates for the months without data were made by graphing the known monthly kwh per unit against the corresponding monthly cooling degree days. Linear regression was used to determine a trendline for this known data, which was then used to estimate the kwh for the unknown months using the degree day data for those months. This process, which is illustrated in Table 1 and Figure 1 below, resulted in a total annual cooling energy estimate of 28.7 MBtu, or 2.84 kbtu/ft 2. Table 2: Monthly Cooling Degree Days and Energy Use (Estimated Va lues in Red) Month Cooling Degree Days Average Monthly Cooling Total Monthly Cooling (kwh) Total Montly Cooling (MBtu) (kwh/unit) January February March April May June July August September October November December Total Figure 1: Linear Regression of Monthly Cooling Degree Days and Energy Use Monthly kwh/unit y = x Cooling Degree Days 4 Southern York County Library M&V Report

8 Fans The energy use for fans during the M&V period was estimated from the run time data logged for representative units from September 2006 to March The total hourly run time during the monitoring period was used along with spot amperage readings and the rated voltage to estimate the total kwh during this period. This was then extrapolated throughout the remainder of the year and across all units to estimate the total annual fan energy consumption of 14.0 MBtu, or 1.38 kbtu/ft 2. Interior Lighting The energy use for interior lighting during the M&V period was estimated from the lighting intensity data logged at 5 locations throughout the building. For each data set, a specific lighting intensity level was defined as the lights being on. Readings taken at each 15 minute interval above this threshold were used to estimate the total hours the lights were on in each space during the measurement period. A count of the number of each type of fixture was made in each space, and spot measurements were made to determine the electric demand of each type of fixture. All of this information was combined to estimate the total lighting energy use during the measurement period, which was then extrapolated throughout the remainder of the year to estimate the total annual interior lighting energy consumption of 79.8 MBtu, or 7.9 kbtu/ft 2. Exterior Lighting No measurements of exterior lighting demand were made, so a count of the number of each type of exterior lighting fixture was made, along with the installed wattages of each type of fixture. Since these fixtures are controlled by photosensors, the exterior lights were assumed to be on during all hours of darkness throughout the year (approximately 4,304 hours). This resulted in a total annual exterior lighting energy consumption of 9.5 MBtu, or 0.94 kbtu/ft 2. Domestic Hot Water The energy use for domestic water heating during the M&V period was estimated from the run time data logged at each electric water heater from April 2006 to August The total hourly run time during this period, along with spot measurements of the current draw and voltage of each unit was used to estimate the kwh during this period. This was extrapolated throughout the remainder of the year, resulting in a total annual domestic water heating energy consumption of 3.9 MBtu, or 0.39 kbtu/ft 2. Electrical Equipment The energy use for most receptacle equipment during the M&V period was estimated from the plugin kwh meter data logged for each type of major equipment. Measurements were taken for the refrigerator, copier, printer, and for representative office, front desk, and card catalog computers. The representative measurements were then used to estimate the total annual electric consumptions based on the quantities of each type of equipment. The public computers available 5 Southern York County Library M&V Report

9 for use in the library were assumed to have similar energy consumptions to the representative office computer. Measurement data was not taken for the water cooler or cabinet unit heater serving the vestibule. The water cooler energy use was estimated from manufacturer s data to be 2 kwh per day, or 730 kwh per year. The cabinet unit heater energy use was estimated by developing a separate energy model consisting of only the vestibule, maintained at 55 F by an electric unit heater using equest v3.6. This model estimated an annual electric consumption of 5 MBtu for the cabinet unit heater. These estimates are summarized in the table below, and result in a total annual known electrical equipment consumption of 31.3 MBtu, or 3.10 kbtu/ft 2. Table 3: Annual Electrical Equipm ent Estimate Equipment kwh/year Number of Total per unit Units kwh/year Refrigerator Office PC Desk PC Desk PC Copier Printer Card Catalog Public PC Water Cooler Unit Heater Total kwh Total MBtu A number of electrical equipment consumptions were not measured, and could not be easily estimated by manufacturer s information or modeled using additional software. These include minor items like phones and fax machines, scanners, receipt printers, clocks, and the attendance counter, and major items like computer monitors, networking equipment, and exhaust fans. The energy consumption of these unknown items was estimated by subtracting the sum of the estimated electric consumptions for cooling, fans, interior and exterior lighting, domestic water heating, and known electrical equipment from the total annual electric consumption from the utility bills. This resulted in a total annual unknown electrical equipment consumption of 27.9 MBtu, or 2.76 kbtu/ft 2. This estimate would prove to be high, and further adjustment is discussed later in this report. The following figure summarizes each of the end use estimates from the M&V period. 6 Southern York County Library M&V Report

10 Figure 2: Annual Energy Consumptions by End Use in MBtu Known Electrical Equipment, 26.3 Exterior Lighting, 9.5 Unknown Electical Equipment, 27.9 Cabinet Unit Heater, 5.0 Heating, Interior Lighting, 79.8 Fans, 14.0 Cooling, 28.7 Domestic Water Heating, 3.9 Energy Model Calibration The ENERGY 10 model of the as designed building was developed during the design process using the ASHRAE Energy Cost Budget Method and the LEED Energy Modeling Protocol. The as built model was adjusted from the as designed model using actual local weather data, occupancy and schedule information, measured data during the M&V period, and utility bills. Actual Weather Data Proper calibration of the energy model requires the use of actual weather data from the M&V period. Hourly weather data was obtained from Weather Underground for York, PA from April 11, 2006 to April 11, This data included temperature, dew point, humidity, sea level pressure, visibility, wind direction, wind speed, precipitation, and cloud conditions. In order to be used in the simulation, this data had to be configured into the format required by ENERGY 10. Additional data not included in the weather data but required by ENERGY 10 were global horizontal radiation, direct normal radiation, diffuse horizontal radiation, and opaque sky cover. The opaque sky cover was estimated first by converting the cloud conditions data, which is listed as clear, scattered clouds, partly cloudy, mostly cloudy, overcast, etc., into a percentage of cloud cover by defining each condition as a specific percentage of cloud cover. This method was validated by 7 Southern York County Library M&V Report

11 summing the percentage of cloud cover for each hour of the year, and comparing it to the sum from a typical meteorological year (TMY2) weather file for Harrisburg, PA. Since no data was available on the three different forms of radiation required by ENERGY 10, these were estimated from the TMY2 file. The radiation values were assumed to be dependent on the time of year, the time of day, and the cloud cover. A reference spreadsheet was created from the TMY2 data for Harrisburg, PA relating each of the radiation parameters to the hour of day and cloud cover values, with a separate table for each month (assuming negligible variation from the beginning to the end of each month). The actual historical radiation values were estimated by looking up values from these reference spreadsheets according to the actual hour, month, and cloud cover data. This data was compiled into the format required by ENERGY 10, and the energy model was revised to reference this file, rather than the previous TMY2 file, for the hourly simulation. Occupancy Schedules Attendance records during the M&V period were obtained from the library staff, in addition to weekly and annual hours of operation, the number of staff and when they arrive. The attendance records were used to estimate the typical daily occupancy and peak occupancy, based on the assumption that each visitor stays for one hour on average. The peak occupancy was input into the energy model, and a percentage of the peak was estimated for each hour of the working day. ENERGY 10 only has the capability to model a single working day schedule throughout the year, with another schedule for nonworking days. Therefore, the variation in operating hours had to be averaged throughout the year to establish a single working day occupancy schedule. The following table summarizes the staff hours used to determine the average daily occupancy of 9 a.m. 6 p.m. Used for Monday Saturday throughout the year in the model. Table 4: Occupancy Schedule Day Weeks Total Staff Staff Hours P er Staff Arrive Leave Year Hours Monday 9:00 a.m. 8:00 p.m Tuesday 9:00 a.m. 8:00 p.m Wednesday 9:00 a.m. 8:00 p.m Thursday 9:00 a.m. 5:00 p.m Friday 9:00 a.m. 5:00 p.m Saturday 9:00 a.m. 5:00 p.m Saturday (Summer) 9:00 a.m. 2:00 p.m Sunday Closed Closed Average Hours Per Day= Southern York County Library M&V Report

12 HVAC Equipment and Schedules The average daily operating hours were also incorporated into the heating and cooling schedules. Temperature profiles were developed for each space from the temperature logging data, and were used to determine a typical morning start up period of 1 hour. This is illustrated in the following figure, which shows the temperature increase during the heating season occurring exactly one hour before occupancy at 9 a.m. as measured by the HOBO datalogger located in the office. Figure 3: Office Daily Temperature Profile (Heating) :00 AM 3:00 AM 6:00 AM 9:00 AM 12:00 PM 3:00 PM 6:00 PM Temperature (F) 9:00 PM 12:00 AM The temperature set points in the model were also updated to match the actual thermostat set points as they are programmed in the library. These are summarized in the following table. Table 5: Thermostat Temperature Settings Mode of Operation Comfort Setting Setback/Setup Heating 70 F 66 F Cooling 74 F 78 F The HVAC system capacities and efficiencies were updated with those of the actual systems installed in the library. Because the energy model only allows one system per zone, and the zones in the as built library are served by multiple systems, their capacities had to be combined to create the HVAC systems in the model. The following table summarizes each HVAC system in the as built library and the corresponding systems in the proposed energy model. 9 Southern York County Library M&V Report

13 Table 6: As Built and As Modeled HVAC Equipment As Built System Number As Built Heating Efficiency (AFUE) Modeled Heating Efficiency E t * As Built Heating Capacity (Btu/h) Modeled Heating Capacity (Btu/h) As Built Cooling Efficiency (SEER) Modeled Cooling Efficiency (EER) As Built Cooling Capacity (Btu/h) Modeled Cooling Capacity (Btu/h) 1 93% 49, , % 95% 49, , , % 37, , % 49, ,500 95% 98, % 49, ,500 Et=thermal efficiency 104,600 81,000 The following figure shows the monthly cooling energy consumptions estimated from the M&V data compared to the energy model outputs. The monthly heating estimates from the M&V period are not available due to the nature of propane deliveries. Figure 4: Estimated vs. Modeled Monthly Cooling Energy Monthly Cooling Energy (Mbtu) M&V Estimate Energy Model Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 10 Southern York County Library M&V Report

14 Interior Lighting The interior lighting power density of each zone in the energy model was updated to reflect the actual installed lighting power densities as determined by the measurement data. The hourly measurements of light readings were used to count the number hours the lights were on in each space during the M&V period by each hour of the day. For example, from 5 p.m. to 6 p.m. the lights were on 93% of the time in the office, but only 62% of the time in the main library spaces. These values were used to estimate the percentage of time the lights were on in the whole building by each hour of the day, which was in turn used to create the hourly lighting schedule in the energy model. The following figures illustrate the percentage of time the lights were on in each space during the M&V period, as well as a comparison of the estimated lighting schedule to that which was input in the model. Figure 5: Percentage of Time Lights on Each Hour by Space 100% 90% Percentage of Time Lights On 80% 70% 60% 50% 40% 30% 20% 10% 0% Office Library Heritage Room Classroom 11 Southern York County Library M&V Report

15 Figure 6: Actual vs. Modeled Lighting Schedule 100% 90% Percentage of Time Lights On 80% 70% 60% 50% 40% 30% 20% 10% 0% Model Actual Exterior Lighting The exterior lighting power density was updated to reflect the actual installed exterior fixtures. The exterior lighting schedules were updated to correspond with the assumptions made about the exterior lighting hours of operation discussed in the Data Analysis section above. The 4304 hours of annual operation used in that estimate equates to roughly 12 hours of daily operation when averaged throughout the year. The peak exterior lighting power was scheduled to operate from 6 p.m. to 6 a.m. in the model. Domestic Hot Water The domestic water heater run time data was collected for each water heater to determine the average run time per hour for unoccupied periods and occupied periods. The average run time per hour for each type of occupancy was used to estimate the hourly energy consumption per hour (Wh/h), which is equivalent to the hourly water heating demand used by the energy model to calculate the energy consumption for this end use. Since the run times were such a small percentage of the total hour for both unoccupied and occupied periods, the actual installed peak wattage had to be reduced to be input into the model. A reduced peak was based on the zone with the highest occupied hourly demand. The hourly demand values were input as a percentage of this reduced peak demand. This data is summarized in the following table. 12 Southern York County Library M&V Report

16 Table 7: Water Heater Run Time and Demand Summary South Zone Water Heater North Zone Water Heater Unocc Occ Unocc Occ Run Time per Hour (min) Wh/h W/ft % of Input Peak 35% 80% 37% 51% Electrical Equipment Since the energy use data for the electrical equipment was based on plug in kwh meters installed on representative pieces of equipment, the actual installed wattage of electrical equipment as well as daily usage profiles for these end uses is still largely unknown. The peak demand of the southwest zone (office, circulation desk, classroom) was assumed to be 1.2 W/ft 2 due to the significant number of computers, office equipment, and refrigerator in this zone. The peak demand of the northeast zone (heritage room, restrooms, main stacks) was assumed to be 0.5 W/ft 2 because there are less than half as many computers, but the water cooler is located in this zone, which uses more energy than two computers or the single refrigerator. A typical demand profile for an office was used, and was edited slightly until the annual energy consumption for the electrical equipment in the modeling results was within an acceptable range of the estimation from the M&V data. The daily demand profile is shown in the figure below. Figure 7: Modeled Hourly Electrical Equipment Demand Profile 0.6 Electrical Equipment Demand (W/sf) SW Zone NE Zone The cabinet unit heater was not modeled since ENERGY 10 does not have the capability of modeling a second heating system in the same zone. The energy consumption could have been added to the 13 Southern York County Library M&V Report

17 electrical equipment consumption, but doing so would have implied that the heat gain from this unit was added to the conditioned space of the building, which is not true. Additionally, ENERGY 10 has no way to only include this consumption in the heating season, so adding additional unrealistic heat gain in the cooling season seemed inappropriate. For these reasons, the cabinet unit heater energy consumption estimated from the separate equest model was manually added to the modeled energy consumption in ENERGY 10. Utility Rates ENERGY 10 can only accept a simple $/kwh and $/kw electric rate, and a $/therm fuel rate, so these values had to be determined from the utility bills. A virtual electric rate of $0.105/kWh was calculated based on the electric bills from the M&V period, and was input as such rather than a separate energy and demand rate. The propane delivery costs were averaged over the billing period to calculate the rate of $1.758/therm. The following table summarizes the energy costs as measured by the utility bills during the M&V period, as well as the results of the energy model. Table 8: Energy Cost Summary Electric Consumption (kwh) Electric Cost Propane Consumption (therms) Propane Cost Metered 57,164 $6, ,433.2 $2, Modeled 57,536 $6, ,579.3 $2, Comparison and Error Analysis The following tables compare the annual energy consumptions by end use for the M&V estimates, the energy modeling results, and the actual utility billing data. Each end use consumption in the calibrated model is within the acceptable 10% error range of the M&V estimate except for heating, which has an error of 10.2%. The higher error in heating consumption is acceptable for a number of reasons. First, the annual heating estimate is based on propane deliveries averaged over a fouryear period. Second, the installed furnaces have been converted to use propane rather than natural gas. The impact of this conversion on the nameplate efficiencies and heat output values of the equipment (as input into the energy model) is unknown. Finally, the energy model is limited to two zones, with a single furnace modeled in each zone. In the actual building there are two furnaces in the southwestern zone and three in the northeastern zone. When each zone in the energy model calls for heat, it is simulated as if all of the furnaces in that zone run simultaneously. In reality, each unit would only run when its individual thermostat called for heat, and all of the units in each zone would often not need to run simultaneously. 14 Southern York County Library M&V Report

18 Table 9: Total Annual Energy Consumption Compariso n by End Use (MBtu) End Use M&V Estimate Energy Model Actual Metered Heating Cooling Fans Hot Water Interior Lighting Exterior Lighting Known Equipment 26.3 Unknown Equipment CUH Total Table 10: Total Annual Energy Consumption Comparison by End Use (kbtu/ft 2 ) End Use M& V Estimate Energy Model Actual Metered Heating Cooling Fans Hot Water Interior Lighting Exterior Lighting Known Equipment 2.6 Unknown Equipment CUH Total The energy use comparisons on an annual basis indicate the M&V estimates and calibrated energy model are very close representations of how the actual building is performing according to the utility billing data. However, a comparison on a monthly level reveals a different story. Monthly gas bills are not available, but the following figure illustrates the monthly electric consumptions of the model and those from the utility bills during the M&V period. 15 Southern York County Library M&V Report

19 Figure 8: Monthly Total Electricity Comparison for M&V Period 8,000 7,000 6,000 Electricity (kwh) 5,000 4,000 3,000 2,000 1,000 0 Utility Bills Modeled Apr 2006 May 2006 Jun 2006 Jul 2006 Aug 2006 Sep 2006 Oct 2006 Nov 2006 Dec 2006 Jan 2007 Feb 2007 Mar 2007 A similar trend can be seen for each year of utility bills since the library has been open. In general, the model is reasonably accurate during the swing months (March, April, May, June, September, October), but has substantial variation in the extreme months. The building is using much less electricity than the model is predicting during the cooling dominated months (July, August), and much more electricity than the model is predicting during the heating dominated months (November, December, January, February). This trend reveals a number of things about the limitations of the modeling software and the accuracy of the estimates made during the M&V period. The accuracy during the swing seasons indicates that the building s base load (lighting, electrical equipment, water heating) has been accurately estimated and modeled, though it is consistently high for most of these months. The variation in the cooling and heating dominated months indicates inaccuracies in end uses which vary seasonally. One end use which is known to vary seasonally is exterior lighting. Because the schedule for exterior lighting had to be input as an annual average, some error would be expected during the periods when the lights would be on significantly shorter or longer than this average. This error would cause the model to under predict exterior lighting energy in the winter, when hours of darkness are the greatest, and over predict exterior lighting energy in the summer, when hours of darkness are the fewest. However, the maximum variation from the average hours of darkness in the summer is 2.8 hours, and the maximum variation in the winter is 2.5 hours. Using these maximum variations as the worst case scenario, the estimates for exterior lighting would be off by no more than 56 kwh for any of the summer months, and no more than 50 kwh for the winter months. This would have little effect on the total error of over 1,000 kwh during these months. 16 Southern York County Library M&V Report

20 Some additional error might be present in the domestic hot water heater consumptions for the winter months, as the water heater energy use was metered from April to August, and occupants are more likely to use hot water in the winter than the summer. However, even if the energy use for water heating doubled during the winter months, it would result in an increase of less than 100 kwh per month, which is less than 10% of the error during these months. The majority of the variation in the cooling and heating dominated months is most likely a result of inaccuracies in the estimates made about and/or modeling of the cooling and heating system. The problem is not likely related to the electricity consumed by ventilation fans, because this would have created a consistently high or low estimate. Part of the difference in the cooling months can be contributed to the shorter weekly operating hours in the summer which had to be averaged out over the year to be input in the energy model. These shorter operating hours would reduce all electric consumption during these months by about 5%, which accounts for some, but not all, of the variation which exists in July and August. A review of the monthly cooling energy comparison between the energy model and the estimate from the M&V period (Figure 4) shows that the energy model was also predicting more cooling energy use during these months than the M&V estimate. Keep in mind that the M&V cooling estimate for July was also stipulated based on the linear regression of cooling energy vs. cooling degree days. All of this would indicate that the majority of the difference between the modeled and metered electricity during July and August is most likely a result of a limitation of the energy model to simulate the actual operation of the air conditioning system. This limitation is the same concept as the one discussed previously to explain the higher modeled gas consumption than the actual propane consumption. The energy model is limited to two zones, with one air conditioning system per zone, while in reality there are two units serving the southwestern zone and three units serving the northeastern zone. When one of these zones calls for cooling in the energy model, it is simulated as if all of the units in that zone are running simultaneously. In reality, each unit would only run when its individual thermostat called for cooling, and all of the units in each zone would often not need to run simultaneously. This limitation would be expected to significantly increase the modeled cooling energy consumption, just as it did to the gas consumption for heating. The likely explanation for the consistently higher metered electric consumption during the heating months than that predicted by the energy model is that the cabinet unit heater in the vestibule (the only source of electric heat in the building) is using significantly more energy than the simple equest energy model had predicted. The building is using more electricity in the heating months than the cooling months, which is very unusual for a building with propane as its main heating fuel. Assuming the difference between the electric consumption modeled in ENERGY 10 and that which was metered by the utility in November, December, January, and February of the M&V period is solely a result of the unit heater, the actual annual consumption of this heater is 7,214 kwh, or 24.6 MBtu. The following table summarizes the monthly energy and cost associated with the unit heater based on this assumption, as well as the equivalent hours of operation each month. 17 Southern York County Library M&V Report

21 Table 11: Estimated Cost of Unit Heater Operation Month Equivalent % of Electricity Cost ($) Hours of Time (kwh) Operation On Nov ,437 $ % Dec ,319 $ % Jan ,627 $ % Feb ,254 $ % Mar $ % Total 7,214 $ ,443 40% The increase in the annual electric consumption estimate of this unit heater required some revision of the M&V estimate for the unknown electrical equipment, since this value was based on the difference between the total billed electricity and the sum of the known electrical end uses (which included the estimate for the unit heater). This revision resulted in a new annual electric consumption for the unknown equipment of 8.3 MBtu, or 0.82 kbtu/ft 2. This value seems to be much more reasonable than the original estimate of 27.9 MBtu, or 2.76 kbtu/ft 2, given the equipment which is included in this category. The energy model was revised with this reduced electrical equipment load, resulting in a decrease in cooling energy and an increase in heating energy. The updated results are summarized below. Figure 9: Revised Annual Energy Consumption by End Use (MBtu) Unknown Electical Equipment, 8.3 Known Electrical Equipment, 26.3 Exterior Lighting, 9.5 Cabinet Unit Heater, 24.6 Heating, Interior Lighting, 79.8 Fans, 14.0 Cooling, 28.7 Domestic Water Heating, Southern York County Library M&V Report

22 Table 12: Total Annual Energy Consumption Comparison by End Use (MBtu) End Use M&V Estimate Energy Model Actual Metered Heating Cooling Fans Hot Water Interior Lighting Exterior Lighting Known Equipment 26.3 Unknown Equipment CUH Total Table 13: Total Annual Energy Consumption Comparison by End Use (kbtu/ft 2 ) End Use M& V Estimate Energy Model Actual Metered Heating Cooling Fans Hot Water Interior Lighting Exterior Lighting Known Equipment 2.6 Unknown Equipment CUH Total The equest model of the vestibule and unit heater was also modified to calibrate the modeled electric consumption of the unit heater to the estimated value of 7,214 kwh per year. This calibration was accomplished by increasing the infiltration rate, which had been admittedly underestimated in the original model, until the electricity consumed by the unit heater was reasonably close to the estimated value. The following figure illustrates the monthly electric consumptions of the revised model (including the equest estimates for the unit heater) and those from the utility bills during the M&V period. 19 Southern York County Library M&V Report

23 Figure 10: Monthly Total Electricity Comparison for M&V Period Electricity (kwh) Utility Bills Modeled 0 Apr 2006 May 2006 Jun 2006 Jul 2006 Aug 2006 Sep 2006 Oct 2006 Nov 2006 Dec 2006 Jan 2007 Feb 2007 Mar 2007 Compared to the original graph, these revised results are significantly more accurate for every month except for October. The cooling variation has decreased, but is not completely eliminated due to the modeling limitations discussed previously which still exist. The swing months are even closer than before because the modeled base load has been reduced to a more accurate level. The greatest impact was in the heating months, which are now within an acceptable range of the metered utility data. One remaining source of error in this data is due to potential weather variation between the equest model and the actual M&V period weather. The equest vestibule model was simulated based on a typical meteorological year s weather data and not the actual weather from the M&V period, so some months like November may have been colder in the M&V period than in a typical year. Another source of error is when the utility meter reading dates were taken. The months in the energy modeling results are the actual calendar months and their corresponding weather data. However, the electric meter readings were never taken on the first of the month, and therefore the consumptions listed for each calendar month do not coincide perfectly with the same time frame from the energy model. For example, November 2006 is 11/1/06 11/30/06 in the energy model, but 11/8/06 12/8/06 by the meter readings. For some months, the reading dates actually create a longer or shorter month than the calendar month. For example, February 2007 was 28 days long and is modeled as such, but the metered month of February is actually 2/7/07 3/12/07, or 33 days. This explains the significantly higher billed electric consumption for February than that which was predicted by the model. Considering these known sources of error, and the additional limitations of the software and M&V measurements, the results were determined to be within an acceptable range of accuracy and the model was assumed to be calibrated. 20 Southern York County Library M&V Report

24 Development of Calibrated Baseline Building In accordance with LEED NC v2.1 EA Credit 1 Optimize Energy Performance, the baseline energy model was developed during the design process using the ASHRAE Energy Cost Budget Method and the LEED Energy Modeling Protocol. Inputs for the baseline building envelope components, lighting values, and equipment efficiencies are consistent with the ASHRAE minimum standards. This original baseline building model also needed to be revised based on the calibration of the proposed building model discussed previously in order for it to be a comparable baseline. The weather data file which was created for the as built energy model was used for the baseline building simulation, as well as the virtual utility rates. The occupancy schedules, interior and exterior lighting schedules, domestic water heating schedules, and electrical equipment schedules were all made identical to the calibrated as built schedules. The peak demand for exterior lighting, domestic water heating, and electrical equipment were also made identical. The HVAC schedules, temperature setpoints, startup period, and outside air flow rates were all copied from the calibrated as built model. The heating and cooling efficiencies were retained from the original baseline building, since these represent the minimum efficiency levels for the equipment. The supply air flow was calculated in the modeling software based on the loads of the baseline building. The calibrated as built HVAC system needed to be autosized to determine the ratio between the actual capacities installed in the building and those determined from the autosizing run. These same ratios were applied to the baseline building capacities determined from the baseline autosizing run according to Section j of ASHRAE The calibrated baseline model was then simulated and compared to the calibrated as built model to determine the calibrated savings. The following tables and figure compare the energy savings by end use as well as total cost savings of the as built model relative to the calibrated baseline, and also provide the same information for the original models developed during the design process and submitted for LEED Certification. 21 Southern York County Library M&V Report

25 Table 14: Energy Summary by End Use of Original Models (Proposed and Budget Buildings) and Calibrated Models (As Built and Baseline) End Use Regulated? Energy Type Proposed Building [kbtu] Budget Building [kbtu] Optimized Energy Performance [%] Calibrated As-Built [kbtu] Calibrated Baseline [kbtu] Optimized Energy Performance [%] Lighting - Conditioned x Electricity 130, , % 78, , % Lighting - Unconditioned x Electricity 4,528 24, % 9,808 49, % Space Heating (Gas) x Gas 221, , % 168, , % Space Heating (Elec) x Electricity ,676 24, % Space Cooling x Electricity 44,036 72, % 29,187 57, % Fans - Interior x Electricity 39,040 52, % 14,134 15,832 Ventilation 89.3% Service Water Heating x Electricity 17,222 17, % 4,093 4, % Office Equipment Electricity 111, , % 34,393 34, % Total Building Consumption 568, , % 363, , % Total Regulated Building Consumption 456, , % 328, , % Figure 11: Energy Summary by End Use Graph of Original Models (Proposed and Budget Buildings) and Calibrated Models (As Built and Baseline) 300,000 Annual Energy Use (kbtu) 250, , , ,000 50,000 Proposed Building Budget Building Calibrated As Built Calibrated Baseline 0 22 Southern York County Library M&V Report

26 Table 15: Energy and Cost Summary by Fuel Type of Original Models Type REGULATED + UNREGULATED Proposed Building Use [kbtu] Proposed Building Cost [$] Budget Building Use [kbtu] Budget Building Cost [$] Proposed / Budget Energy Cost % % Electricity (Total) 346,898 $9, ,886 $13,241 71% 71% Gas (Total) 221,594 $2, ,940 $2,652 76% 76% Total (Regulated + Unregulated) 568,492 $11, ,826 $15,893 73% 72% Type REGULATED ONLY Proposed Building Use [kbtu] Proposed Building Cost [$] Budget Building Use [kbtu] Budget Building Cost [$] Proposed / Budget Energy Cost % % Electricity (Total) 235,241 $6, ,228 $10,204 63% 63% Gas (Total) 221,594 $2, ,940 $2,652 76% 76% Total (Regulated Only) 456,835 $8, ,168 $12,856 69% 65% Percent Savings = (Budget $ - Proposed $)/Budget $ = 34.5% Table 16: Energy Cost Summary by Fuel Type of Calibrated Models Calibrated Calibrated Calibrated Calibrated As-Built / Baseline As-Built As-Built Baseline Baseline Type Use [kbtu] Cost [$] Use [kbtu] Cost [$] Energy % Cost % REGULATED + UNREGULATED Electricity (Total) 194,714 $6, ,328 $10,297 58% 58% Gas (Total) 168,290 $2, ,770 $4,409 67% 67% Total (Regulated + Unregulated) 363,004 $8, ,098 $14,705 62% 61% Calibrated Calibrated Calibrated Calibrated As-Built / Baseline As-Built As-Built Baseline Baseline Type Use [kbtu] Cost [$] Use [kbtu] Cost [$] Energy % Cost % REGULATED ONLY Electricity (Total) 160,321 $4, ,935 $9,234 54% 54% Gas (Total) 168,290 $2, ,770 $4,409 67% 67% Total (Regulated Only) 328,611 $7, ,705 $13,643 60% 58% Percent Savings = (Budget $ - Proposed $)/Budget $ = 42.0% 23 Southern York County Library M&V Report

27 Conclusions The Southern York County Library performs 42% better than the calibrated baseline building, which is based on the ASHRAE Energy Cost Budget and represents a minimally codecompliant building. These savings are 7.5% higher than the savings estimated during the design process by the energy models created for LEED EA Credit 1 Optimize Energy Performance. Because the savings are within 10% of the original energy modeling results, the savings are assumed to have been verified. In addition to performing better than an ASHRAE Energy Cost Budget building and the predicted performance of the designed building, the Southern York County Library also uses less energy than other libraries in York County and similar buildings nationwide. In 2007 the average energy use intensity of libraries monitored by the York County Community Foundation s Energy Program was 54.9 kbtu/ft 2. At 33.0 kbtu/ft 2 in 2007, Southern York County Library was 40% better than the average and the best performing library in the group. Using the Environmental Protection Agency s Energy Star Target Finder program, the library s performance during the M&V period achieved an energy performance rating of 95. This means that the library used less energy than 95% of similar buildings nationwide when adjusted for weather variations and basic operating conditions of each building. This is only an approximation of the library s relative performance, since the comparison had to be made to a typical office due to the limited number of building types available in the database used by Target Finder. Energy Cost Saving Opportunities to Consider Despite the exceptional performance of the library compared to these benchmarks, the M&V analysis has revealed room for significant additional improvement. The fact that the building is consuming more electricity in the winter than the summer has exposed the costly nature of the cabinet unit heater in the vestibule. Our estimates indicate this unit could be using over $750 worth of electricity each year. Further monitoring would be necessary to confirm the accuracy of this estimate, but it is undeniable that the unit heater s operation is costly. The necessity of running this heater at the current settings, or at all, should be evaluated. Another option to consider is providing an additional supply duct from one of the existing air handlers to serve the vestibule in place of the unit heater. This would be sized to supply a relatively small quantity of heated air to the vestibule in the winter to temper the space, and could be closed for all other seasons. Even if this duct supplied the equivalent amount of heating as the current estimate for the unit heater, changing the heating source from electricity to propane would still save approximately $325 each year. Additional energy savings could be achieved with greater unoccupied temperature setback in the winter and setup in the summer. The current thermostat settings only allow 4 of setback and setup, which is modest for the installed systems, which can typically recover from much steeper setback and setup. An additional simulation with the energy model using unoccupied temperature 24 Southern York County Library M&V Report