Overview Building Features Grade JK-6 Grade 7-12

Pre-Construction Energy Savings Report

  1. Introduction

  2. Analysis of the Dr. David Suzuki Public School
  3. Individual Design Measures Evaluation Compared to MNECB
  4. Comparison with Other Energy Efficient Schools
  5. Conclusions and Recommendations
  6. References

  7. Appendix: Life Cycle Cost Analysis
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List of Figures:

Figure 1: Light Shelf Schematic
Figure 2: Sun Tube Schematic
Figure 3: Sun Tracker Schematic

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List of Tables:

Table 1: Energy Results Summary
Table 2: Electrical Demand Summary
Table 3: Window Types Used in Building Model
Table 4: Performance Details of Water-to-Water Heat Pumps
Table 5: Performance Details of Water-to-Air Heat Pumps
Table 6: Detailed Energy Results
Table 7: Greenhouse Gas Emission Factors
Table 8: Life Cycle Cost Analysis Results
Table 9: Energy Summary for MNECB Reference (Electric Base Case)
Table 10: Energy Summary for MNECB Reference (Natural Gas Base Case)
Table 11: Envelope Parameters
Table 12: Results from Analysis of Envelope Measure
Table 13: Results from Analysis of GSHP Measure
Table 14: Results from Analysis of Displacement Ventilation Measure
Table 15: Results from Analysis of Energy Recovery Measure
Table 16: Results from Analysis of Daylighting Measure
Table 17: Results from Analysis of Light Shelves Measure
Table 18: Results from Analysis of Solera Panels Measure
Table 19: Results from Analysis of Sun Tube Measure
Table 20: Results from Analysis of Sun Tracker Measure
Table 21: Results from Analysis of Occupancy Sensors Measure
Table 22: Results from Analysis of Green Roof Measure
Table 23: Results from Analysis of Solar PV Measure
Table 24: Results from Analysis of Solar Hot Water Measure
Table 25: Results from Analysis of Solar Wall Measure
Table 26: Results from Analysis of Wind Turbine Measure
Table 27: Summary of Estimated Greenhouse Gas Savings
Table 28: Life Cycle Cost Analysis for Electric Base Case
Table 29: Life Cycle Cost Analysis for Natural Gas Base Case
Table 30: Life Cycle Cost Analysis for Electric Base Case with Carbon Offset Savings
Table 31: Life Cycle Cost Analysis for Natural Gas Base Case with Carbon Offset Savings
Table 32: Comparison of School Energy Efficiency Measures
Table 33: Comparison of Operating Schedules
Table 34: Comparison of Energy Results by End-Use
Table 35: Electricity Rates
Table 36: Natural Gas Rates
Table 37: Comparison of Annual Energy Cost and Greenhouse Gas Production

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Nomenclature

 

AHU Air Handling Unit
ASHRAE American Society of Heating, Refrigerating and Air-Conditioning Engineers
CO2 Carbon Dioxide: A greenhouse gas
COP Coefficient of Performance: Ratio of energy output to energy input
DOE United States Department of Energy
DHW Domestic Hot Water
DX Direct Expansion: Indicates refrigerant-based air conditioning
EER Energy Efficiency Ratio: Same as COP, except measuring units are (BTU/h)/W
ekWh Equivalent kilowatt-hours: Energy unit of non-electrical sources presented inkWh instead of the customary unit (i.e. m3, BTU, Therm).
FIT Feed-in Tariff
GHG Greenhouse Gas
GSHP Ground Source Heat Pump
HVAC Heating, Ventilating, and Air Conditioning
IGU Insulated Glazing Unit: Window
kWh Kilowatt-hour
LCC Life cycle cost
MNECB Model National Energy Code for Buildings
PV Photovoltaic
R-value A measure of thermal resistance
RSI-value A measure of thermal resistance (specifically in SI units)
SHGC Solar Heat Gain Coefficient
U-value A measure of thermal conductance
USI-value A measure of thermal conductance (specifically in SI units)
VAV Variable Air Volume
VRV Variable Refrigerant Volume
VT Visible Transmittance

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Executive Summary

 

The Dr. David Suzuki Public School, located in Windsor, Ontario is a new school construction that highlights numerous green energy saving technologies. The purpose of this study was to assess the estimated energy savings and the associated cost benefit of the green design measures proposed for the building and to provide guidance to others involved in school design. This assessment was based on the tender drawings issued on April 1, 2009. Any subsequent changes to the design have not been assessed.

The report consists of three parts. Chapter 2 describes the building and its energy efficient features and provides an estimate of the overall energy use of the building. Chapter 3 provides others interested in improving school designs with an idea of the energy savings associated with each measure used in the Dr. David Suzuki School. We compared the energy saving of each design feature, one at a time, to a school constructed to the Model National Energy Code for Buildings (MNECB). This will allow one to see savings attributable to each measure and decide on its merits for their design. Chapter 4 provides a comparison of the Dr. David Suzuki design with another school from the Greater Essex School Board and two others from the York Region.

Table I presents the modelled performance of the Dr. David Suzuki School compared to the Model National Energy Code for Buildings (MNECB). The building is electrically heated and there is an estimated 64% energy saving compared to a building built to MNECB minimum requirements.

Table I: Dr.David Suzuki Energy Use Compared to the MNECB

  Electricity (MJ) Natural Gas (MJ) Total (MJ) Total (MJ/m2) Energy Cost Cost / m2
Proposed 1,256,436 0 1,256,436 246 $31,580 $6.19
Reference 3,560,504 0 3,560,504 698 $90,763 $17.79
Savings 2,304,068 0 2,304,068 452 $59,183 $11.60

Table II presents results of the energy cost savings predicted for each of the measures in isolation compared to a school constructed to the MNECB. Both electric and gas boiler heating cases are presented in the table. Detailed descriptions of the measures can be found in Chapter 2.

Table II: Annual Energy Cost Savings Compared to MNECB

Measure Electric Boiler Case Gas Boiler Case
Envelope $14,195 $7,005
GSHP $25,262 $6,415
Displacement Ventilation $3,668 $1,912
Heat Recovery $7,983 $4,964
Daylighting $687 $1,560
Light Shelves $851 $1,167
Solera Panels $627 $637
Sun Tubes $624 $688
Sun Tracker $134 $173
Occupancy Sensors $1,678 $2,897
Green Roof $1,253 $599
Solar PV $4,593 $4,865
Solar Hot Water $363 $413
Solar Wall $447 $151
Wind Turbine $337 $386

The annual energy cost and greenhouse gas production of the Dr. David Suzuki school is
compared in Table III to three other modern schools; another in Greater Essex County and two
from the York Region. Annual operating cost is considerably lower in the Dr. David Suzuki case
by 35% to 45%.

Table III: Comparison of Annual Energy Use and Greenhouse Gas Emissions

School Annual Energy Cost
Annual Greenhouse Gas Production
  ($) ($/ft2) (tonnes) (kg/ft2)
Dr. David Suzuki Public School $31,580 $0.575 85.2 1.55
Essex Public School $53,533 $0.790 201.5 2.97
Woodbridge Catholic School $45,783 $0.872 166.7 3.17
Donald Cousens Public School $51,813 $0.898 189.7 3.29

The Dr. David Suzuki school as a whole was estimated to have a payback period of 18 years when compared to a natural gas heating MNECB reference case. The estimated total incremental cost was $1,750,000 and yielded total electricity (energy and demand), natural gas, water and carbon offset savings of just under $71,400. Maintenance savings are estimated to be another $19,900 per year.

Many of the design features in Dr. David Suzuki School improve the quality of the classrooms and improve the learning experience for the students and the environment for the teachers. These benefits are difficult to quantify financially. For example, research [1] has shown that children achieve significantly higher test marks in classrooms that are daylit than in those that are not. Daylighting is one of the best building related investments for the learning environment [1]. The non-energy benefits of the measures applied to Dr.David Suzuki School are discussed in Chapter 2.

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1. Introduction

 

The Dr. David Suzuki Public School, located in Windsor, Ontario is a new school construction that highlights numerous green energy saving technologies. The purpose of this study is to assess the estimated energy savings and the associated cost benefit of certain green energy saving technologies proposed for the building, based on the tender drawings issued on April 1, 2009. Any subsequent changes to the design have not been assessed.

The following green energy saving technologies are assessed:

Although there are several other technologies used in this building, they are not covered within
the scope of this study.

Many of the measures listed above have benefits beyond energy savings that have not been quantitatively assessed in this report. Many improve the quality of the classrooms and improve the learning experience for the students and the environment for the teachers. In the sections that follow there is brief discussion of these other benefits. We have not monetized these other benefits as it was beyond the scope of our mandate. Readers are encouraged to learn more about the non-energy benefits of advanced school designs.

The annual operating cost and energy usage of the building was estimated by modelling using EE4 and took into account all the energy saving measures. A life cycle cost analysis for the whole design was completed as well.

To show the benefits of the individual energy measures listed above, the proposed MNECB building model was created and the energy and demand savings for each individual measure were evaluated on this model. Similar to the whole building economic analysis, a life cycle cost and discounted payback period for each individual energy measure was performed.

Finally, a whole building comparison was performed between Dr. David Suzuki Public School, Essex Public School, Woodbridge Catholic School Expansion #4, and Donald Cousens Public School. The differences between these four buildings are described and an energy end use comparison is provided.

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2. Analysis of the Dr. David Suzuki Public School

2.1. Predicted Energy and Demand Savings Compared to MNECB

Based on Caneta modelling, Dr. David Suzuki Public School has 64.7% energy savings compared the MNECB building and 65.2% energy cost savings (See Table 1). The peak winter and summer demand savings are estimated to be 471.3kW and 141.2kW, respectively (See Table 2). The utility rates were common in all building models. Rates were based on Essex General Service (50kW to 2,999 kW) for electricity and Union Gas Rate M2 for natural gas, and are summarized later in Table 35 and Table 36, respectively. All cost values in this report are $2009.

Table 1: Energy Results Summary

  Electricity (MJ) Natural Gas (MJ) Total (MJ) Total (MJ/m2) Energy Cost Cost / m2
Proposed 1,256,436 0 1,256,436 246 $31,580 $6.19
Reference 3,560,504 0 3,560,504 698 $90,763 $17.79
Savings 2,304,068 0 2,304,068 452 $59,183 $11.60


Note: The results for the Proposed building are based on the assumption that the electricity generated by the solar PV is used in the building. In reality, this electricity will be sold under the FIT program.

Table 2: Electrical Demand Summary

  Winter Demand Summer Demand
Proposed 134.3kW 110.0kW
Reference 605.6kW 251.4kW
Savings 471.3kW 141.2kW

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2.2. Description of Energy and Water Saving Technologies

The following sections provide a description of the energy saving technologies implemented. The benefits of each technology are discussed and compared to the MNECB reference building where applicable. The individual scenario analysis is done in Section 3.

2.2.1. Wall, Roof and Fenestration

The building envelope minimizes the amount of heat lost or gained between the interior and outdoors. The walls, roof and windows make up the building envelope and the better the building envelope, the greater the energy savings due to a reduction in heat loss or heat gain. The building envelope also affects acoustic comfort as it attenuates site and traffic noise. The building shell also affects thermal comfort because building interior surface temperature may be cold or hot and affects the radiant temperature of the space and comfort of occupants.

The Dr. David Suzuki Public School is made up of 13 different wall constructions. The predominant wall types are insulated with 4"of polyurethane spray insulation or 2.5" of polyurethane spray insulation and 3.5" of mineral fibre insulation. The overall building thermal resistance in SI units is 4.07m2oC/W. The MNECB reference building has a wall thermal resistance of 2.12m2oC/W.

There are two roof constructions in the building. The main roof is insulated with 5.5" of polystyrene insulation and is used throughout the entire building. The green roof covering the kindergarten and day care area is similar to the main roof but has 4" of soil for vegetation and a waterproofing membrane. The full benefits of the green roof are described in Section 2.2.7. The school has an overall roofing RSI value of 5.17m2oC/W. The reference MNECB building has a roof RSI value of 2.39m2oC/W.

The windows are aluminum framed, double glazed, low-e, argon filled with a non-metallic spacer. There are five different window assemblies to control the amount of solar heat gain and daylight transmission into the building. The properties of the window types used in the building are summarized in Table 3.

Table 3: Window Types Used in Building Model

Glazing Unit Window Type U-valve (W/m2oC) SHGC VT
IGU-1 Fixed 1.94 0.36 0.59
Operable 2.31 0.36 0.59
Curtain Wall 2.22 0.36 0.59
IGU-2 Fixed 1.94 0.29 0.52
IGU-3 Insulated Spandrel N/A N/A 0.0
IGU-4 Fixed 1.94 0.47 0.68


Notes: IGU-3 was modeled as a spandrel panel instead of a window. SHGC is the solar heat gain coefficient needed to calculate solar gain through the window and VT is the visible transmittance of the window type.

The fifth window type is the Solera panel discussed in Section 2.2.4.

The overall building window u-value is 2.01W/m2oC. The MNECB reference building has a window u-value of 3.23W/m2oC. The percentage glazing in both buildings is 24%.

2.2.2. Ground Source Heat Pump System

Ground source heat pump systems save energy because they use solar energy stored in the upper layers of the earth. Ground source heat pump systems reduce heat island effect as waste heat is returned to the ground and not the outside air. Since the piping is buried underground, damage caused by inclement weather and vandalism are greatly reduced. These systems provide better aesthetics since no equipment needs to be placed on rooftops or outside the building envelope. Cooling towers are eliminated and the mechanical room space in a building can be smaller.

A ground source heat pump (GSHP) system is used to heat and cool the school. A water-ethanol solution is circulated through 28 boreholes each 370 feet deep pre-conditioning the fluid to 40oF during the winter and approximately 85oF during the summer. Four water-water heat pumps provide the hot and chilled water throughout the school to provide the heating and cooling. Two water-air heat pumps (Gymnasium cooling only) and two water-cooled condensing units (serve the VRV system and refrigerant piping) make up the other units.

The water-to-water heat pumps provide both heating and cooling for the school. The make and performance details (at AHRI standard rating conditions) are summarized in Table 4.

Table 4: Performance Details of Water-to-Water Heat Pumps

Heat Pump Qty Heating Cup COP Cooling Cap COP
McQuay WGRW1360 2 219,311 BTU/hr 2.92 230,905 BTU/hr 4.20
McQuay WGRW1300 2 178,679 BTU/hr 2.76 179,908 BTU/hr 4.01

Notes: COP is the coefficient of performance and is a measure of the output divided by input to a heat pump in both heating and cooling. AHRI standard rating conditions for water-to-water heat pumps in heating are source/load entering water temperatures of 32ºF/104ºF. AHRI standard rating conditions for cooling are source/load entering water temperatures of 77ºF/53.6ºF.

The water-to-air heat pumps are dedicated cooling units serving the gymnasium. Two watercooled condensers are used to provide refrigerant to the fan coil units located throughout the school. The performance details are summarized in Table 5.

Table 5: Performance Details of Water-to-Air Heat Pumps

Heat Pump/Condenser Qty Heating Cup COP Cooling Cap COP
McQuay WFVF1060 2 0 BTU/hr N/A 61,300 BTU/hr 4.7
Daikin RWEYQ84MTJU 2 0 BTU/hr N/A 84,000 BTU/hr 4.4

Notes: COP is the coefficient of performance and is a measure of the output divided by input to a heat pump in both heating and cooling. The performance details of the McQuay equipment are given at AHRI standard rating conditions for water-to-air heat pumps in cooling: 80.6ºF dry bulb/66.2ºF wet bulb entering air temperature and 77ºF entering water temperature. The performance details of the Daikin equipment are given at the manufacturer's nominal conditions of 80ºF dry bulb/67ºF wet bulb entering air temperature and 85ºF entering water temperature.

Overall, the central heating and cooling plant has the following capacity and efficiency:

Heating: 795,000 BTU/hr, COP = 2.84
Cooling: 1,111,225 BTU/hr, COP = 4.22

The MNECB reference building, has an electric boiler with a COP = 1.0 and a reciprocating chiller with a COP of 3.8.

2.2.3. HVAC System – Displacement Ventilation and Energy Recovery

Displacement ventilation is a method of distributing ventilation air (outdoor air) to a space in an efficient manner. Heating and cooling the ventilation air is a major component of the school's energy consumption. Traditional systems introduce and exhaust the ventilation air at the ceiling level. In a displacement ventilation system, the supply air is introduced at the floor level in the classroom and exhausted at the ceiling level resulting in a better airflow distribution. The improvement in distribution can allow up to a 20% reduction in ventilation air volume as per ASHRAE Standard 62.1. With a displacement ventilation system, air quality improves because contaminants from room occupants and other sources tend to rise out of the breathing zone rather than being mixed in the space.

To further treat the ventilation air, the school uses air-to-air enthalpy recovery wheels and the warmer or cooler air to condition the outdoor air. The energy recovery wheels have heat recovery effectiveness between 68% to 76% and are installed on each of the five air handling units. The MNECB reference building has no energy recovery.

2.2.4. Daylighting Controls – Daylight Sensors, Light Shelves, Solera Panels

The use of daylight sensors, light shelves and Solera panels for daylighting control are only beneficial in perimeter spaces where there is sufficient window area and daylight is available. Lighting contributes a significant portion of building energy usage. Going beyond simply installing more efficient light fixtures, numerous lighting technologies are available to further reduce lighting consumption. In particular, optimizing the use of natural daylighting can lead to improved lighting energy savings. Research has shown that children achieve significantly higher test marks in classrooms that are daylit than in those that are not [1]. Daylighting is one of the best building related investments for the learning environment.

Daylight sensors installed in classrooms and corridors dim the interior lighting when daylight is able to meet the lighting requirements of the space. Typically, the light fixtures on the outer walls in the classrooms are controlled with daylight sensors. Clerestories in the corridors permit daylight to enter classrooms through windows in classrooms on the corridor side.

Light shelves are a highly reflective horizontal ledge located at a high level of a window. The light shelf surface reflects the incoming daylight deeper into the space resulting in potentially longer daylighting periods. In the school, light shelves are installed in several south-facing classrooms. The interior classroom light fixtures are controlled on/off when daylighting is sufficient. Figure 1 illustrates how a light shelf works.

Figure1: Light Shelf Schematic

Light shelf SchematicSolera panels are similar to light shelves, but replace a pane of glass above the visibility range. Solera panels use a translucent honeycomb structure to spread the daylight further into the room and reduce the glare.

The use of daylighting control devices in the school helped reduce the lighting energy by an additional 18%. The reference MNECB building does not consider daylighting technology.

 

 

 

 

 

2.2.5. Sun Tube and Sun Tracker Skylights

For interior spaces, natural light can be delivered to the space through sun tubes or sun trackers.

Sun tubes are simply a domed shaped skylight installed on a highly reflective tube. The tubes are installed on and extend through the roof of a building and allow light from different angles to be reflected down the pipe into the space below. The amount of light captured changes with the angle of sun – the projected skylight surface area is not constant. The sun tubes are installed throughout the school and are predominantly located in the gymnasium, which has limited exterior windows. Other areas include the corridors, stairwells, mechanical room and interior reception offices. A sun tube is shown in Figure 2.

Sun trackers are similar to sun tubes but have reflective aluminum panels which track the sun across the sky. Essentially, the sun tracker maximizes the amount of daylight delivered to the space by keeping the sunlight capturing area constant. Two sun trackers are installed in the kindergarten cubbies area. A sun tracker is depicted in Figure 3.

Figure 2: Sun Tube Schematic

Sun Tube Schematic

Figure 3: Sun Tracker Schematic

Sun Tracker Schematic

2.2.6. Lighting Occupancy Controls

Lighting designs can be further optimized with the use of occupancy sensors. Occupancy sensors de-energize the room lighting when the room is unoccupied. When people return to the space, the ceiling mounted occupancy sensors recognize the movement and re-energize the lights. The school uses occupancy sensors in the washrooms, mechanical rooms and classrooms. The reference MNECB building uses no occupancy control.

2.2.7. Green Roof

A green roof is a roof that is partially or completely covered with vegetation and soil, or a growing medium, planted over a water proofing membrane. Other than the added insulation benefit of the soil and water proofing membrane, green roofs lower the building roof temperature during the summer through evaporative cooling. By lowering the roof temperature, a significant portion of the cooling load can be offset, especially in buildings that have high internal heat gains. Additional benefits include providing an amenity space, fruit, vegetable and flower growth; increase of the roof life span; reduction in storm water run off to reduce peak loads on sewer systems; to filter pollutants and CO2 out of the air and filter pollutants and heavy metals out of rainwater. They also help to mitigate heat island effect. Some cons are cost, structural load and maintenance.

The school's green roof is located over the kindergarten, day care, the east wing entrance corridor and mechanical room. On average it is expected that the roof temperature is 40oF to 80oF lower during the summer. The total green roof area is 5,000ft2. The MNECB Reference building does not account for the insulation or reduced surface temperature benefit of a green roof.

2.2.8. Solar Technologies – PV, Solar Hot Water Heating, Solar Wall

Numerous solar technologies can be used as well to offset heating or electrical loads. Photovoltaic (PV) panels convert solar radiation into electricity that is sold back to the grid. Solar walls and solar hot water collectors can be installed to preheat the outdoor air or domestic hot water using the solar energy. The MNECB building does not incorporate any of these technologies.

The school's south facing, grid-tied, PV system consists of 165 Sharp 224W PV modules. The panels are located on a truss system spanning two stories. It is estimated that the system is capable of producing approximately 50,000 kWh of electricity annually. Under the feed in tariff system (FIT) program the supplier of the PV panels anticipated the grid sales would be worth $25,000 annually over 20 years.

The school domestic hot water is heated through one 4.5kW electric hot water heater. The water is preheated through a solar hot water heating system consisting of two 30ft2 solar collectors. The collectors are mounted on the roof and face South to optimize the solar energy available. The estimated energy savings from the solar hot water collector are 4,300kWh annually – approximately 17.5% of the DHW load.

The ventilation air for AHU-3, serving the day care and administration offices, is preheated with a solar wall during the heating season. The outdoor air is transferred through a south facing 160ft2 solar wall, which can preheat the ventilation air up to 18.3oC during the heating season. The solar wall offsets the ventilation-heating load by approximately 5,000kWh annually.

2.2.9. Wind Turbine

Wind turbines harness the power of the wind and convert it into electricity. The amount of electricity produced is dependent on the size of the wind turbine and average amount of wind speed.

The school has a small Skystream 3.7 wind turbine installed 60ft above the ground capable of producing 2.4kW of electricity. Taking into account energy losses and varying wind speed, the expected annual electricity savings generated from the wind turbine are 4,000kWh.

2.2.10. Rain Water Harvesting

Rainwater harvesting is a popular water saving design measure. This water can be used to supply dependable potable or non-potable water. Rain falling on the roof is collected by roof drains and directed to two 10,000L underground cisterns. The water is filtered and treated and used in flushing toilets and to provide non-potable water to exterior hose bibs, reducing the use of municipally treated potable water. Based on the analysis performed by Enermodal, the expected savings of potable water is 1,675 m3 per year. Sewer costs are reduced as well.

2.2.11. Storm Water Retention

Storm water retention is used to store water on site until it is lost through percolation. Vegetation or growing mediums are typically used and help avoid storm water runoff, reducing the load for municipal water treatment. This can also improve health of on-site soils, vegetation and habitat areas.

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2.3. Energy Model Results by End-Use

Table 6 summarizes the energy breakdown for the proposed and reference MNECB building.

Table 6: Detailed Energy Results

Proposed design Energy End-Uses
Load Electricity, kWh

Total, ekWh/ft2

Lighting 67,193 1.22
Miscellaneous 29,582 0.54
Space Heating 77,551 1.41
Space Cooling 46,982 0.86
Heat Rejection 0 0.00
Pumps 94,668 1.72
Fans 67,311 1.23
DHW 20,112 0.37
Renewable -54,389 -0.99
Totals 349,010 6.36
Proposed design Energy End-Uses
Load Electricity, kWh

Total, ekWh/ft2

Lighting 159,878 2.91
Miscellaneous 29,582 0.54
Space Heating 462,181 8.42
Space Cooling 41,961 0.76
Heat Rejection 42,480 0.77
Pumps 64,168 1.17
Fans 83,389 1.52
DHW 105,390 1.92
Renewable 0 0.00
Totals 989,029 18.01

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2.4. Water Savings

Rainwater Harvesting for use in flushing toilets is not an energy saving measure for the building. In fact, the additional pumping and filtration requirements of the system are likely to result in an increase in energy consumption. However, there will be operating savings through reduced water and sewer charges because the municipally treated water that would otherwise be used is displaced by rainwater. Based on the current water and sewer rates obtained from the Windsor Utilities Commission [1][3], and the water savings calculated by Enermodal, the expected annual savings for the proposed rain water capture system is $1,756 per year.

Storm water retention is not an energy or water saving measure for the building, however it is of societal benefit because it reduces the load on municipal water treatment plants.

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2.5. Greenhouse Gas Savings

The use of fossil fuels and electricity is associated with the production of greenhouse gases (GHGs). For fossil fuels, the GHGs are produced on site during combustion, and are relatively constant for a particular fuel type. If fossil fuels are used to generate electricity, GHGs will be produced at the site of generation. In Ontario, the quantity of GHG production per kWh of electricity fluctuates because there are many sources of electricity, including GHG producers (coal and natural gas) and non-producers (hydroelectric, nuclear, and renewables). The GHG emission factors (i.e. in terms of grams of equivalent CO2 per unit of energy) used in this report are based on a study on air pollution in the City of Toronto [4] and are summarized in Table 7.

Table 7: Greenhouse Gas Emission Factors

Natural Gas 2,057g eCO2/m3
Electricity 244g eCO2/kWh

The emission factor for electricity is the one that was in effect in 2004, and includes a multiplier of 1.10 to account for transmission and distribution losses [4]. The emission factor for natural gas provided in [4] did not include losses due to leakage. The leakage rate is estimated to be 0.33% by volume based on a study on emissions factors [5], and this was incorporated into the emission factor for natural gas used in this analysis.

The calculation of GHG savings requires the multiplication of the expected energy savings with the appropriate emission factor. Based on the results in Table 6 and excluding the solar PV electricity generation (which will be used under the FIT program), the estimated GHG savings are 143.9 tonnes per year as shown below:

(989,029 -399,369) kWh/year 244g eCO /kWh 1,000,000 g/tonne 143.9 tonnes/year.

For this study, the cost of "Gold Standard" carbon offsets1 was used to estimate the economic value of the GHG savings. These carbon offsets are valued at $41.925 per tonne, equal to the average of the costs charged by two providers of these offsets: Planetair [7] and Less [8]. Therefore, the economic benefit of the GHG savings in this building is $6,033 per year (143.9 tonnes*$41.925).

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2.6. Life Cycle Cost and Discounted Payback Period

A life cycle cost (LCC) analysis was performed on the measures incorporated in the building to determine if the future net savings (including maintenance and utility costs) offset the incremental capital cost. For more information on this analysis method and terminology used here, see the Appendix.

Maintenance costs are estimated based principally on RS Means [9]. Savings for lighting measures are based on the expected delay in periodic lamp replacement. Additional maintenance cost information was obtained from [10] for GSHPs and chillers, [11] for wind turbines, and [12] for solar PV. Incremental capital costs are based on Hanscomb [13] and RS Means [14].

For the discounted payback analysis, a discount rate of 5% was used together with natural gas and electricity cost escalation rates of 2% per year. These percentages are all net of inflation. Maintenance, water, and carbon offset costs were not escalated. The results of the LCC analysis are presented in Table 8.

Table 8: Life Cycle Cost Analysis Results

Carbon Offset Savings Considered Simple Payback Period (years) Discounted Payback Period (years) Net Present Value Savings
No 17.5 >20 ($306,233)
Yes 16.5 >20 ($231,061)

Notes: Results take into account income from the solar PV generation under the FIT program. Discounted Payback Period: the period required for the incremental capital cost to be offset by the discounted net savings in operating costs. Net Present Value Savings: the sum, over the analysis period, of each year's energy cost savings discounted to the present, minus the original capital cost. See Appendix for more information.

The life cycle cost calculator used for this analysis does not report discounted payback periods in excess of 20 years because this is considered to be the effective life of a typical mechanical system.

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3. Individual Design Measures Evaluation Compared to MNECB

To evaluate the individual measures, the school was modelled with MNECB requirements. One measure at a time was implemented into EE4 to assess the energy and cost savings available for that measure. The expected annual energy usage, demand and energy cost for the reference MNECB building is summarized in Table 9.

Table 9: Energy Summary for MNECB Reference (Electric Base Case)

Annual Energy Usage 989,029kWh

Summer Peak Demand

251.5kW
Winter Peak Demand 605.6kW
Annual Energy Cost $90,763

It should be noted that the above MNECB building uses an electric hot water boiler for heating and a reciprocating water-cooled chiller for cooling.

A second MNECB base case scenario was created with a natural gas boiler with 80% thermal efficiency (more typical of other schools). This is considered more representative of most schools in Ontario and of interest to other readers. The expected energy usage, demand and energy cost for this MNECB (natural gas) base building is summarized in Table 10.

Table 10: Energy Summary for MNECB Reference (Natural Gas Base Case)

Annual Electric Usage 526,859kWh

Annual Natural Gas Usage

24,656therms
Summer Peak Demand 251.4kW
Winter Peak Demand 167.9kW
Annual Energy Cost $71,916

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3.1 Energy Savings

The following sections summarize the energy savings, demand savings, and cost savings associated with each measure evaluated. A description of each measure is provided along with a description of the changes made to the MNECB reference file and any assumptions made in the evaluation. The Tables in this section provide the whole building energy use and savings with each measure applied, compared to the MNECB Reference case in Table 9 or Table 10. To evaluate each measure, each was applied to the MNECB reference base case and analysed one at a time. After the measure was implemented, the equipment capacities (boiler, chiller, and cooling tower) were resized, using the same equipment sizing factors as in the MNECB reference base case.

3.1.1. Wall, Roof and Fenestration

The building envelope was upgraded to the same levels as that of the proposed building (See Table 11).

Table 11: Envelope Parameters

Envelope MNECB RSI/u-value Upgraded RSI/u-value
Wall 2.13m2oC/W 4.07m2oC/W
Roof 2.39m2oC/W 5.17m2oC/W
Window 3.23W/m2oC 2.01W/m2oC

The overall roof RSI value includes the insulation benefit of the green roof on the kindergarten classrooms.

Simulating the MNECB buildings with the improved building envelope resulted in approximately a 33% reduction in heating for both cases. This would be expected since during the winter months the heat loss is reduced by the improvement in insulation levels. The same improvement for cooling might also be expected, however, since the majority of the school is closed during the summer, no cooling benefit was available. Table 12 summarizes the final energy consumption, demand and energy cost and relevant savings.

Table12: Results from Analysis of Envelope Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Envelope Savings Envelope Savings
Annual Electricity Usage 34,071kWh 154,958kWh 528,603kWh -1,744kWh
Annual Natural Gas Usage - - 16,242therms 8,414therms
Summer Peak Deman 251.2kW 0.3kW 251.2kW 0.2kW
Winter Peak Demand 536.9kW 68.7kW 171.7kW -3.8kW
Annual Energy Cost $76,568 $14,195 $64,911 $7,005

3.1.2. Ground Source Heat Pump System

The ground source heat pump system specified in the proposed building was implemented into the MNECB buildings with the heat pumps resized to meet the required peak heating and cooling capacities with the same sizing factor as calculated for the reference building. The heating and cooling COPs were left unchanged. To ensure the correct pumping power is taken into account, the proposed building's pump static pressure, efficiency and variable speed control were modeled as well. The pump flow was set to the MNECB requirement of 3 GPM/ton of cooling.

Modeling the MNECB buildings with the GSHP, the heating energy consumption was reduced by over 50% and the cooling by almost 40%. There was a slight increase in pumping power because of the associated pumping required for the ground heat exchanger. Heating and cooling energy savings are attributed to the improved performance of the heat pumps over an electric boiler and reciprocating chiller. The results of the measure are summarized in Table 13.

Table 13: Results from Analysis of GSHP Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  GSHP Savings GSHP Savings
Annual Electricity Usage 713,514kWh 275,515kWh 713,514kWh -186,655kWh
Annual Natural Gas Usage - - 0therms 24,656therms
Summer Peak Deman 238.1kW 13.4kW 238.1kW 13.3kW
Winter Peak Demand 331.0kW 274.6kW 331.0kW -163.1kW
Annual Energy Cost $65,501 $25,262 $65,501 $6,415

Note: The GSHP energy cost savings compared to the MNECB building with a natural gas boiler are not as good as the MNECB building with electric boiler since the natural gas rates are fairly low ($0.29/m3).

3.1.3. HVAC System – Displacement Ventilation System and Energy Recovery

Two HVAC system upgrades were separately evaluated – the displacement ventilation system and the energy recovery on all five air handling units.

To evaluate the displacement ventilation system, the MNECB building was modeled at the proposed building's design outdoor air (20% decrease in outdoor air). With a reduction in outdoor air, the heating and cooling energy decreased as well. An 8% decrease in heating and 2% decrease in cooling resulted. The results are summarized in Table 14. More heating savings than this were expected, since the school is not fully operational during the warmer summer months.

Table 14: Results from Analysis of Displacement Ventilation Measure MNECB with Electric Boiler MNECB with Natural Gas

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Displacement Ventilation Savings Displacement
Ventilation
Savings
Annual Electricity Usage 948,746kWh 40,283kWh 524,400kWh 2,459kWh
Annual Natural Gas Usage - - 22,692therms 1,964therms
Summer Peak Deman 248.4kW 3.1kW 248.5kW 2.9kW
Winter Peak Demand 547.2kW 58.4kW 167.6kW 0.3kW
Annual Energy Cost $87,095 $3,668 $70,004 $1,912

Modeling the heat recovery in the MNECB building, approximately 20% heating energy savings were obtained. The heat recovery was modeled on all HVAC systems with effectiveness between 0.68 to 0.76 depending on the system. Cooling energy savings were approximately 1.5%. The results are summarized in Table 15.

Table 15: Results from Analysis of Energy Recovery Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Energy Recovery Savings Energy Recovery Savings
Annual Electricity Usage 901,737kWh 87,292kWh 523,121kWh 3,738kWh
Annual Natural Gas Usage - - 19,257therms 5,399therms
Summer Peak Deman 250.0kW 1.5kW 246.6kW 4.8kW
Winter Peak Demand 354.6kW 251kW 167.6kW 0.3kW
Annual Energy Cost $82,780 $7,983 $66,952 $4,964

3.1.4. Daylighting Controls – Daylight sensors, Light Shelves, Solera Panels

To evaluate the daylighting benefit the following steps were taken to evaluate each measure.

Daylighting
Daylight sensors were added to each relevant space with the sensor located as shown on the electrical drawings. The fraction of lighting controlled by the daylight sensors was calculated for each space and applied towards the MNECB lighting design. The visible transmittance of the windows was changed from 0.9 (default) to the proposed building's values. The Solera windows, not taken into account for this measure, had their visible transmittance set to insulating glazing unit 1 (IGU-1). Running the energy model, the daylight sensors reduced the lighting energy by approximately 12%. The results are summarized in Table 16.

Table 16: Results from Analysis of Daylighting Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Daylighting Savings Daylighting Savings
Annual Electricity Usage 981,219kWh 7,810kWh 503,971kWh 22,888kWh
Annual Natural Gas Usage - - 25,419therms -763therms
Summer Peak Deman 238.2kW 13.3kW 238.2kW 13.2kW
Winter Peak Demand 606.8kW -1.2kW 162.9kW 5.0kW
Annual Energy Cost $90,076 $687 $70,356 $1,560

Note: Since a reduction in lighting results in an increase in required space heating, the energy cost results are much better for a building with natural gas heating.

Light shelves
To account for the light shelves, it was assumed that the other principal lights in the room would be manually controlled (on/off) when there was sufficient daylight. The impact of the light shelves results in an additional 9% lighting energy savings and 1% increase in heating energy. The results are summarized in Table 17. Savings are compared to the MNECB building with daylight sensing control already implemented.

Table 17: Results from Analysis of Light Shelves Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Light Shelves Savings Light shelves Savings
Annual Electricity Usage 971,948kWh 9,271kWh 489,741kWh 14,230kWh
Annual Natural Gas Usage - - 25,662therms -243therms
Summer Peak Deman 229.3kW 8.9kW 229.3kW 0kW
Winter Peak Demand 607.2kW -0.4kW 162.9kW 9.0kW
Annual Energy Cost $89,225 $851 $69,188 $1,167

Note: The day care classroom has light shelves installed without daylight sensors. It was assumed the lights would be manually turned off when there was sufficient lighting.

Solera Panels
In addition to diffusing the daylight, the Solera panels have an improved insulation value over the regular window. The Solera panel improved the lighting energy savings by approximately 4%, without causing an increase in heating. The results are summarized in Table 18.

Table 18: Results from Analysis of Solera Panels Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Light Shelves Savings Light shelves Savings
Annual Electricity Usage 974,392kWh 6,827kWh 497,734kWh 6,237kWh
Annual Natural Gas Usage - - 25,379therms 40therms
Summer Peak Deman 233.8kW 4.4kW 233.9kW 4kW
Winter Peak Demand 605.5kW 1.3kW 163.0kW 0kW
Annual Energy Cost $89,449 $627 $69,719 $637

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3.1.5. Sun Tube and Sun Tracker Skylights

The following assumptions were made to estimate the energy savings associated with sun tubes and sun trackers skylights:

To estimate the lighting energy savings from the sun tube and sun tracker, the available daylighting luminosity was calculated and assumed to replace the number of light fixtures capable of meeting that lighting level. For the reference MNECB buildings, it was assumed that the lighting installed had an efficacy of 85 lumens/watt (T12 fixture, DOE 2009).

Sun Tubes
A total of 30 sun tubes are located throughout the building. Since no lighting control strategy was shown for the spaces with sun tubes installed, the following control strategy was assumed:

Table 19: Results from Analysis of Sun Tube Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Sun Tube Savings Sun Tube Savings
Annual Electricity Usage 981,904kWh 7,125kWh 519,734kWh 7,125kWh
Annual Natural Gas Usage - - 24,656therms 0therms
Summer Peak Deman 246.3kW 5.2kW 246.2kW 5.2kW
Winter Peak Demand 601.2kW 4.4kW 163.5kW 4.4kW
Annual Energy Cost $90,139 $624 $71,228 $688

Sun Tracker
Two sun trackers are installed above the cubbies area in the kindergarten. It was assumed that the lights in the kindergarten would be controlled through continuous dimming. The sun trackers resulted in just over 1.1% lighting energy savings. The MNECB building results are summarized in Table 20.

Table 20: Results from Analysis of Sun Tracker Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Sun Tracker Savings Sun Tracker Savings
Annual Electricity Usage 987,240kWh 1,789kWh 525,070kWh 1,789kWh
Annual Natural Gas Usage - - 24,656therms 0therms
Summer Peak Deman 249.1kW 2.4kW 249.0kW 2.45kW
Winter Peak Demand 603.2kW 2.4kW 165.5kW 2.45kW
Annual Energy Cost $90,629 $134 $71,743 $173

3.1.6. Lighting Occupancy Controls

The EE4 modeling manual estimates that the use of occupancy sensors reduces the energy use for lighting by 30%. Using the same occupancy sensor control fraction as found in the proposed building, the expected energy savings are presented in Table 21.

Table 21: Results from Analysis of Occupancy Sensors Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Occupancy Sensors Savings Occupancy Sensors Savings
Annual Electricity Usage 970,427kWh 18,602kWh 487,683kWh 39,176kWh
Annual Natural Gas Usage - - 25,697therms -1,041therms
Summer Peak Deman 235.2kW 16.3kW 235.2kW 16.2kW
Winter Peak Demand 604.1kW 1.5kW 151.1kW 16.8kW
Annual Energy Cost $89,085 $1678 $69,019 $2,897

3.1.7. Green Roof

The green roof not only provides an increased insulation level, but also lowers the roof temperature through evaporative cooling. To estimate the potential energy savings from the green roof, it is assumed that the roof temperature is at the outdoor wet bulb temperature during the summer. Knowing the indoor and roof temperature, the space cooling load reduction was estimated. The results are summarized in Table 22.

Table 22: Results from Analysis of Green Roof Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Green Roof Savings Green Roof Savings
Annual Electricity Usage 975,056kWh 13,973kWh 526,563kWh 29,582kWh
Annual Natural Gas Usage - - 23,986therms 670therms
Summer Peak Deman 251.3kW 0.2kW 251.3kW 0.1kW
Winter Peak Demand 600.7kW 4.9kW 167.8kW 0.1kW
Annual Energy Cost $89,529 $1,253 $71,317 $599

3.1.8. Solar Technologies – PV, Solar Hot Water Heating, Solar Wall

The energy supply and savings from the PV, Solar Hot Water and Solar Wall were estimated using RetScreen in the overall building analysis.

Photovaltaic Panels
The estimated electricity savings from the 165 PV panels were 50,359kWh. RetScreen was unable to provide to a good estimate for the demand savings during the summer and winter. To take the demand savings into account, the monthly electricity production was calculated from RetScreen. Assuming electricity production is constant during the month the daily electricity production was then divided by the number of expected operating hours per day (January: 9 hours, June: 13 hours). The results are summarized in Table 23. In reality, all power from the PV array will be sold to the grid under the FIT program.

Table 23: Results from Analysis of Solar PV Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Solar PV Savings Solar PV Savings
Annual Electricity Usage 938,670kWh 50,359kWh 476,500kWh 50,359kWh
Annual Natural Gas Usage - - 24,656therms 0therms
Summer Peak Deman 238.5kW 13.0kW 238.4kW 13kW
Winter Peak Demand 593.2kW 12.4kW 155.5kW 12.4kW
Annual Energy Cost $86,170 $4,593 $67,052 $4,865


Solar Hot Water Heating
Two solar hot water collectors were installed to offset some of the domestic hot water load. Because of the increased domestic hot water usage in the reference building (no low-flow faucets), the solar hot water collectors were only capable of preheating 5% of the reference DHW. To estimate the winter and summer demand savings, RetScreen was used to estimate the monthly energy savings from which the hourly electricity savings were calculated. The results are summarized in Table 24.

Table 24: Results from Analysis of Solar Hot Water Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Solar Hot Water Savings Solar Hot Water Savings
Annual Electricity Usage 984,749kWh 4,280kWh 522,579kWh 4,280kWh
Annual Natural Gas Usage - - 24,656therms 0therms
Summer Peak Deman 250.3kW 1.2kW 250.2kW 1.2kW
Winter Peak Demand 604.7kW 0.9kW 167.0kW 0.9kW
Annual Energy Cost $90,400 $363 $71,503 $413


Solar Wall
A 15m2 solar wall is installed to preheat the outdoor air during the winter for AHU-3. In the proposed building, 865 CFM of outdoor air was preheated. The MNECB reference building has 1031cfm. Using the same solar wall area and increased outdoor airflow, the estimated annual solar wall savings is 5,200kWh or 177therms. Since the solar wall does not operate during the summer months, only the winter demand savings were calculated for the MNECB building with electric boiler. The results are summarized in Table 25.

Table 25: Results from Analysis of Solar Wall Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Solar Wall Savings Solar Wall Savings
Annual Electricity Usage 983,829kWh 5,200kWh 526,859kWh 0kWh
Annual Natural Gas Usage - - 24,479herms 177therms
Summer Peak Deman 251.5kW 0.0kW 251.4kW 0kW
Winter Peak Demand 602.7kW 2.9kW 167.9kW 0kW
Annual Energy Cost $90,316 $447 $71,765 $151


3.1.9. Wind Turbine

A small wind turbine is installed at the school. The electricity savings were calculated from RetScreen with the turbine performance characteristics set to a predefined turbine model. The estimated annual electricity savings were 4,000kWh. The results are summarized in Table 26.

Table 26: Results from Analysis of Wind Turbine Measure

  MNECB with Electric Boiler
MNECB with Natural Gas Boiler
  Wind Turbine Savings Wind Turbine Savings
Annual Electricity Usage 985,029kWh 4,000kWh 522,859kWh 4,000kWh
Annual Natural Gas Usage - - 24,656herms 0therms
Summer Peak Deman 251.0kW 0.5kW 250.9kW 0.5kW
Winter Peak Demand 605.1kW 0.5kW 167.4kW 0.5kW
Annual Energy Cost $90,426 $337 $71,530 $386

3.1.10. Rain Water Harvesting

As described in Section 2.4, the expected annual savings for the proposed rain water capture system is $1,756 per year.

3.1.11. Storm Water Retention

The storm water retention system is not expected to result in an operational cost savings.

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3.2. Greenhouse Gas Savings

The calculation of GHG savings requires the multiplication of the expected energy savings with the appropriate emission factor, as described in Section 2.5. The results for the two different reference base cases (electricity versus gas boiler) are presented in Table 27.

Table 27: SUmmary of Estimated Greenhouse Gas Savings

Measure Greenhouse Gas Saved per Year (Tonnes)
  Electric Base Case Natural Gas Base Case
Envelope 37.8 47.9
GSHP 67.2 96.1
Displacement Ventilation 9.8 11.9
Heat Recovery 21.3 31.9
Daylight Sensors 1.9 1.2
Light Shelves 4.2 3.3
Solera Panels 3.6 3.0
Sun Tube 1.7 1.7
Sun Tracker 0.4 0.4
Occupancy Sensors 4.5 3.6
Green Roof 3.4 3.9
Solar PV 0.0 0.0
Solar Hot Water 1.0 1.0
Solar Wall 1.3 1.0
Wind Turbine 1.0 1.0
Rain Water Capture 0.0 0.0
Storm Water Retention 0.0 0.0
As Designed 143.9 172.8


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3.3. Life Cycle Cost and Discounted Payback Period

A life cycle cost analysis was performed on the measures individually, applied to the MNECB Reference, considering incremental capital costs, maintenance costs, and utility costs (including natural gas, electricity, water, and carbon offsets). Sources for the estimates may be found in Section 2.6. Changes in the size of plant equipment (boiler, chiller, and cooling tower) are considered in evaluating the incremental capital cost of a measure.

For the analysis, a discount rate of 5% was assumed, as were electricity and natural gas cost escalation rates of 2%. Maintenance, water, and carbon offset costs were not escalated. The results are provided in four tables. Table 28 and Table 29 contain results for the electric and natural gas base cases, respectively, where the value of the carbon offsets is not considered. Table 30 and Table 31 contain results for the electric and natural gas base cases, respectively, where the value of the carbon offsets is considered. "As Designed" refers to the design of the Dr. David Suzuki Public School, which includes all of the measures.

The payback period for the energy recovery measure is relatively long. This is because the VAV system (assumed in MNECB Reference) has a supply air temperature set point of 55°F in heating, and the remainder of the heating load is met by reheat coils and in-floor heating in the zone. In other words, the heat recovery wheel will only recover heat to maintain a mixed air supply temperature of 55°F. Since the VAV system is a recirculating system, the mixed air temperature without heat recovery is already close to the required supply temperature set point of 55°F. Therefore, only a small amount of heat recovery is required to meet the supply temperature set-point, after which the heat recovery is shut-off.

The payback period for the Solar PV measure was less than 20 years when the generated electricity was sold under Ontario's FIT Program. It was estimated that the PV panels would result in benefit under FIT of $25,000 per year.

The payback period for the Solar Hot Water and Wind Turbine measures would be reduced if the installations were larger. As designed, the hot water and electricity contributions from these measures are small relative to the expected building loads.

Table 28: Life Cycle Cost Analysis for Electric Base Case

Measure Set Incremental Captial
Cost
Incremental Maintenance Cost Electricity Savings Natural
Gas
Savings
Water Savings Simple
Payback
(years)
Discounted Payback
(years)
Internal
Rate of
Return
Net
Present
Value
Envelope $253,932 $482 $14,195 $0 $0 18.5 > 20 2.8% ($47,605)
GSHP $287,769 ($22,530) $25,262 $0 $0 6.0 7.0 17.0% $370,893
Displacement Ventilation ($3,057) $0 $3,668 $0 $0 immediate immediate infinite $57,926
Heat Recovery $190,330 $113 $7,983 $0 $0 24.2 >20 0.2% ($72,327)
Daylight Sensors $10,086 ($451) $687 $0 $0 8.9 10.9 10.8% $5,814
Light Shelves $21,494 ($720) $851 $0 $0 13.7 19.7 5.1% $205
Solera Panels $5,082 ($580) $627 $0 $0 4.2 4.7 24.7% $11,525
Sun Tubes $39,200 ($149) $624 $0 $0 50.7 >20 -6.1% ($28,004)
Sun Tracker $7,000 ($38) $134 $0 $0 40.8 >20 -4.5% ($4,528)
Occupancy Sensors $35,479 ($777) $1,678 $0 $0 14.5 >20 4.8% ($694)
Green Roof $247,078 $0 $1,253 $0 $0 197.2 >20 -14.3% ($228,335)
Solar PV $458,000 $4,580 $25,000 $0 $0 22.4 >20 1.3% ($141,109)
Solar HW $15,900 $365 $363 $0 $0 infinite >20 n/a ($15,019)
Solar Wall $7,750 $0 $447 $0 $0 17.3 >20 3.4% ($1,063)
Wind Turbine $37,000 $740 $337 $0 $0 infinite >20 n/a ($41,181)
Rain Water $79,000 $132 $0 $0 $1,756 48.6 >20 -7.3% ($58,761)
Storm Water $45,800 $0 $0 $0 $0 - >20 - ($45,800)
As Designed $1,756,212 ($18,832) $79,780 $0 $1,756

17.5

>20 3.0% ($306,233)


Notes: Incremental Capital Cost is the difference in cost compared to the base case for the measure analysed. Incremental Maintenance Cost is the average annual maintenance and repair cost over 20 years compared to the base case.

Table 29: Life Cycle Cost Analysis for Natural Gas Base Case

Measure Set Incremental Captial
Cost
Incremental Maintenance Cost Electricity Savings Natural
Gas
Savings
Water Savings Simple
Payback
(years)
Discounted Payback
(years)
Internal
Rate of
Return
Net
Present
Value
Envelope $252,922 $482 ($168) $7,174 $0 38.8 >20 -3.6% ($154,144)
GSHP $277,304 ($23,584) ($14,606) $21,022 $0 9.2 12.2 9.3% $112,571
Displacement Ventilation ($3,912) $0 $238 $1,675 $0 immediate immediate infinite $32,513
Heat Recovery $188,050 $113 $361 $4,603 $0 38.8 >20 -3.7% ($115,204)
Daylight Sensors $10,106 ($451) $2,211 ($651) $0 5.0 5.6 21.2% $18,859
Light Shelves $21,519 ($720) $1,375 ($207) $0 11.4 15.0 7.4% $4,914
Solera Panels $5,082 ($580) $602 $34 $0 4.2 4.7 24.9% $11,669
Sun Tubes $39,200 ($149) $688 $0 $0 46.8 >20 -5.5% ($27,043)
Sun Tracker $7,000 ($38) $173 $0 $0 33.3 >20 -2.8% ($3,947)
Occupancy Sensors $35,536 ($777) $3,784 ($888) $0 9.7 11.9 9.9% $17,482
Green Roof $247,009 $0 $29 $571 $0 412.1 >20 -18.2% ($238,042)
Solar PV $458,000 $4,580 $25,000 $0 $0 22.4 >20 1.3% ($141,109)
Solar HW $15,900 $365 $413 $0 $0 328.2 >20 -11.1% ($14,264)
Solar Wall $7,750 $0 $0 $151 $0 51.4 >20 -5.8% ($5,493)
Wind Turbine $37,000 $740 $386 $0 $0 infinite >20 n/a ($40,442)
Rain Water $79,000 $132 $0 $0 $1,756 48.6 >20 -7.3% ($58,761)
Storm Water $45,800 $0 $0 $0 $0 - >20 - ($45,800)
As Designed $1,745,746 ($19,886) $39,911 $21,022 $1,756 21.1 >20 1.0% ($564,555)

Notes: Incremental Capital Cost is the difference in cost compared to the base case for the measure analysed. Incremental Maintenance Cost is the average annual maintenance and repair cost over 20 years compared to the base case.

Table 30: Life Cycle Cost Analysis for Electric Base Case with Carbon Offset Savings

Measure Set Incremental Captial
Cost
Incremental Maintenance Cost Electricity Savings Natural
Gas
Savings
Water Savings Carbon
Offset
Savings
Simple
Payback
(years)
Discounted Payback
(years)
Internal
Rate of
Return
Net
Present
Value
Envelope $253,932 $482 $14,195 $0 $0 $1,585 16.6 >20 3.7% ($27,850)
GSHP $287,769 ($22,530) $25,262 $0 $0 $2,818 5.7 6.6 18.0% $406,017
Displacement Ventilation ($3,057) $0 $3,668 $0 $0 $412 immediate immediate infinite $63,061
Heat Recovery $190,330 $113 $7,983 $0 $0 $893 21.7 >20 1.1% ($61,199)
Daylight Sensors $10,086 ($451) $687 $0 $0 $80 8.3 10.1 11.7% $6,809
Light Shelves $21,494 ($720) $851 $0 $0 $175 12.3 17.2 6.2% $2,382
Solera Panels $5,082 ($580) $627 $0 $0 $150 3.7 4.1 27.7% $13,391
Sun Tubes $39,200 ($149) $624 $0 $0 $73 46.3 >20 -5.5% ($27,096)
Sun Tracker $7,000 ($38) $134 $0 $0 $18 36.9 >20 -3.8% ($4,300)
Occupancy Sensors $35,479 ($777) $1,678 $0 $0 $190 13.4 18.7 5.5% $1,678
Green Roof $247,078 $0 $1,253 $0 $0 $143 177.0 >20 -13.8% ($226,554)
Solar PV $458,000 $4,580 $25,000 $0 $0 $0 22.4 >20 1.3% ($141,109)
Solar HW $15,900 $365 $363 $0 $0 $44 380.5 >20 -11.9% ($14,473)
Solar Wall $7,750 $0 $447 $0 $0 $53 15.5 >20 4.4% ($401)
Wind Turbine $37,000 $740 $337 $0 $0 $41 infinite >20 n/a ($40,671)
Rain Water $79,000 $132 $0 $0 $1,756 $0 48.6 >20 -7.3% ($58,761)
Storm Water $45,800 $0 $0 $0 $0 $0 - >20 - ($45,800)
As Designed $1,756,212 ($18,832) $79,780 $0 $1,756 $6,032 16.5 >20 3.5% ($231,061)

Notes: Incremental Capital Cost is the difference in cost compared to the base case for the measure analysed. Incremental Maintenance Cost is the average annual maintenance and repair cost over 20 years compared to the base case.

Table 31: Life Cycle Cost Analysis for Natural Gas Base Case with Carbon Offset Savings

Measure Set Incremental Captial
Cost
Incremental Maintenance Cost Electricity Savings Natural
Gas
Savings
Water Savings Carbon
Offset
Savings
Simple
Payback
(years)
Discounted Payback
(years)
Internal
Rate of
Return
Net
Present
Value
Envelope $252,922 $482 ($168) $7,174 $0 $2,009 29.6 >20 -1.9% ($129,110)
GSHP $277,304 ($23,584) ($14,606) $21,022 $0 $4,029 8.1 10.4 11.1% $162,785
Displacement Ventilation ($3,912) $0 $238 $1,675 $0 $498 immediate immediate infinite $38,722
Heat Recovery $188,050 $113 $361 $4,603 $0 $1,339 30.4 >20 -2.1% ($98,522)
Daylight Sensors $10,106 ($451) $2,211 ($651) $0 $50 4.9 5.5 21.7% $19,487
Light Shelves $21,519 ($720) $1,375 ($207) $0 $137 10.6 13.8 8.2% $6,626
Solera Panels $5,082 ($580) $602 $34 $0 $124 3.8 4.2 27.4% $13,212
Sun Tubes $39,200 ($149) $688 $0 $0 $73 43.1 >20 -4.9% ($26,134)
Sun Tracker $7,000 ($38) $173 $0 $0 $18 30.6 >20 -2.3% ($3,719)
Occupancy Sensors $35,536 ($777) $3,784 ($888) $0 $150 9.3 11.4 10.4% $19,351
Green Roof $247,009 $0 $29 $571 $0 $164 323.4 >20 -17.3% ($235,995)
Solar PV $458,000 $4,580 $25,000 $0 $0 $515 22.4 >20 1.3% ($141,109)
Solar HW $15,900 $365 $413 $0 $0 $44 172.4 >20 -9.9% ($13,718)
Solar Wall $7,750 $0 $0 $151 $0 $43 40.0 >20 -4.4% ($4,961)
Wind Turbine $37,000 $740 $386 $0 $0 $41 infinite >20 n/a ($39,932)
Rain Water $79,000 $132 $0 $0 $1,756 $0 48.6 >20 -7.3% ($58,761)
Storm Water $45,800 $0 $0 $0 $0 $0 - >20 - ($45,800)
As Designed $1,745,746 ($19,886) $39,911 $21,022 $1,756 $7,708 19.4 >20 1.7% ($474,292)

Notes: Incremental Capital Cost is the difference in cost compared to the base case for the measure analysed. Incremental Maintenance Cost is the average annual maintenance and repair cost over 20 years compared to the base case.

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4. Comparison with Other Energy Efficient Schools

To provide context for the energy results of Dr. David Suzuki Public School, the results were compared to the modelled energy results of three other energy efficient schools. The schools chosen for the comparison are:

  1. Essex Public School (Greater Essex County District School Board),
  2. Woodbridge Catholic School Expansion #4 (York Catholic District School Board), and
  3. Donald Cousens Public School (York Region District School Board)

Following is a description of the other schools, any changes that were required for consistent modelling, and the modelled energy results. For the purposes of this comparison, electricity generated by the solar PV array in Dr. David Suzuki Public School was assumed to be used onsite and not sold under the FIT program.

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4.1. Description of Measures in other School Designs

Table 32 contains a comparison of Dr. David Suzuki Public School and the other three schools with respect to the major components such as the envelope, plant, ventilation and lighting. Note that the remainder of measures incorporated into Dr. David Suzuki Public School may be found in Section 2.2.

Table 32: Comparison of School Energy Efficiency Measures

Building Measure Dr. David Suzuki
Public School
Essex
Public School
Woodbridge
Catholic School
Donald Cousens
Public School
Heating Plant and Efficiency GSHP:
COP = 2.84
Boiler:
87% thermal,
condensing
Boiler:
87% thermal,
fully modulating
Boiler:
85.2% thermal
Cooling Plant and Efficiency GSHP:
COP = 4.22
DX Cooling:
EER = 8.6~9.3
DX Cooling:
EER = 10.1
Air-cooled chiller:
COP = 2.8;
DX in AHU:
EER = 10.1
Average Heat Recovery Effectiveness on All Outdoor Air 74% 52% 39% 22%
Wall RSI 4.07 1.92 2.27 3.34
Roof RSI 5.17 3.36 3.08 3.85
Window USI 2.01 3.41 1.90 2.66
Demand Controlled Ventilation Yes, for 14.1% of floor area Yes, for 14.3% of floor area Yes, for 9.6% of
floor area
No
Lighting Power Density (W/m2) 8.01 9.17 9.70 9.47

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4.2. Energy Modelling

4.2.1. Essex Public School

A pre-existing model (originally prepared for Union Gas incentive programs) of Essex Public School was used for this analysis. To provide a more appropriate comparison with Dr. David Suzuki Public School, the orientation of the building and the operating schedules of the air handling units were changed.

4.2.2. Woodbridge Catholic School

A pre-existing model (originally prepared for NRCan's Commercial Building Incentive Program) of Woodbridge Catholic School was used for this analysis. The city weather file and orientation of the building were changed to match those of Dr. David Suzuki Public School. As designed, Woodbridge Catholic School has cooling for only about 21% of its floor area. Cooling was added to the remaining areas of the building to be consistent with the design of Dr. David Suzuki Public School. The cooling type was direct expansion to match the type already used in the building. The modelled cooling efficiency was EER = 10.1 to be consistent with the efficiencies of the existing equipment. Where cooling was added to a constant volume multizone system, the system type was changed to variable air volume, as would be typical of a multizone system with cooling in a school. The operating schedules of the air handling units were also changed.

4.2.3. Donald Cousens Public School

A pre-existing model (originally prepared for NRCan's ecoENERGY Program) of Donald Cousens Public School was used for this analysis. The city weather file and orientation of the building were changed to match those of Dr. David Suzuki Public School. As designed, Donald Cousens has cooling for only about 13% of its floor area. Cooling was added to the remaining areas of the building: An air-cooled chiller (COP = 2.8) with a capacity of 95.7 tons was added to provide chilled water to the classrooms because they already incorporate a fan coil-like system, and direct expansion cooling (EER = 10.1) was modelled in the AHU serving the gymnasium. The operating schedules of the air handling units were also changed.

4.2.4. Schedules

A common alteration to the models of the three schools was to the operating schedules, to more closely resemble those used for Dr. David Suzuki Public School. It was not possible to make the schedules identical because the arrangement of the air handling systems is different between the schools.

Table 33 shows the proportions of each building (by floor area) that were modelled with a particular schedule. The differences in schedule would result in a corresponding difference in energy use.

Table 33: Comparison of Operating Schedules

Schedule Name Schedule Dr. David Suzuki
Public School
Essex
Public School
Woodbridge
Catholic School
Donald Cousens
Public School
Main Classrooms M-F 10 hours/day
No summer operation
60.3% 74.7% 77.2% 79.3%
Office and Daycare M-F 12 hours/day
Summer operation
7.7% 11.0% 13.2% 13.4%
Gym and Corridor M-F 10 hours/day
Summer operation
32.0% 14.3% 9.6% 7.4%

4.2.5. Modelling Results

The energy and peak electricity demand results are presented in Table 34. The table also contains results normalized by floor area to provide a better comparison between schools.

Table 34: Comparison of Energy Results by End-Use

Building
Energy
Use
Dr. David Suzuki Public School Essex Public School Woodbridge Catholic School Donald Cousens Public School
Electricity
kWh
Total
ekWh/ft2
Electricity
kWh
Natural Gas
Therm
Total
ekWh/ft²
Electricity
kWh
Natural Gas
Therm
Total
ekWh/ft²
Electricity
kWh
Natural Gas
Therm
Total
ekWh/ft²
Lighting 67,193 1.22 129,328 0 2.46 98,140 0 1.87 105,306 0 2.01
Misc. 29,582 0.54 33,844 0 0.64 28,382 0 0.54 32,221 0 0.61
Space Heating 77,551 1.41 0 16,436 9.17 0 10,211 5.70 0 12,875 7.18
Space Cooling 46,982 0.86 59,116 0 1.13 46,040 0 0.88 41,195 0 0.78
Pumps 94,668 1.72 26,644 0 0.51 103,495 0 1.97 116,603 0 2.22
Fans 67,311 1.23 52,320 0 1.00 40,092 0 0.76 78,785 0 1.50
DHW 20,112 0.37 0 5,846 3.26 0 5,373 3.00 0 4,248 2.37
Renewable -54,389 -0.99 0 0 0.00 0 0 0.00 0 0 0.00
Totals 349,010 6.36 301,252 22,282 18.17 316,149 15,584 14.72 374,110 17,123 16.68
Peak Electricity Demand
kW 134.3 262.6 164.0 227.8
W/ft2 2.45 3.88 3.12 3.95

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4.3. Annual Energy Cost and Greenhouse Gas Production

The utility rates were made common in all building models. Rates were based on Essex General Service (50kW to 2,999 kW) for electricity and Union Gas Rate M2 for natural gas, and are summarized in Table 35 and Table 36, respectively.

Table 35: Electricity Rates

Item Cost
Meter Charge $344.76
Cost per kWh $0.06066
Cost per peak kW $6.1099

Table 36: Natural Gas Rates

Item Cost
Meter Charge $70.00
Cost per m3 $0.29

Annual greenhouse gas production was estimated for the schools using emission rates of 244g eCO2/kWh of electricity and 2,057g eCO2/m3 of natural gas. These rates, which include transmission losses, were based on a study of greenhouse gases in the City of Toronto [15].

The annual energy cost and greenhouse gas production for each school is presented in Table 37. The table also contains the results normalized by floor area to provide a better comparison between schools.

Table 37: Comparison of Annual Energy Cost and Greenhouse Gas Production

School Annual Energy Cost
Annual Greenhouse Gas Production
  ($) ($/ft2) (tonnes) (kg/ft2)
Dr. David Suzuki Public School $31,580 $0.575 85.2 1.55
Essex Public School $53,533 $0.790 201.5 2.97
Woodbridge Catholic School $45,783 $0.872 166.7 3.17
Donald Cousens Public School $51,813 $0.898 189.7 3.29

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5. Conclusions and Recommendations

5.1. Energy Efficiency

The Dr.David Suzuki public school uses anywhere from 35% to 45% of the energy of recent energy efficient school designs compared here. Peak electrical demand was significantly lower as well – anywhere from 30 kW to over 128 kW when compared to recent energy efficient designs.

Renewable systems in the design displace an estimated 54,000 kWh of electricity use – or about 13% of the total. Renewable systems were not used in other schools in the comparison.

Dr. David Suzuki had average heat recovery effectiveness of 74% on all outdoor air, whereas the other three schools had only between 22% and 52%. This would significantly reduce energy use.

Lighting power density was 8.0 W/m2 while the other schools averaged about 9.5 W/m2.

While the other three schools in the comparison had condensing (high efficiency) or near condensing boilers, the ground source heat pump system in Suzuki had heating energy use15- 25% of that of the other schools.

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5.2. Cost/Benefit

The Dr. David Suzuki school as a whole was estimated to have a payback period of 18 years when compared to a natural gas heating MNECB reference case. The estimated total incremental cost was $1,750,000 and yielded total electricity (energy and demand), natural gas, water and carbon offset savings of just under $71,400. Maintenance savings were estimated to be another $19,900 per year.

The economics of individual energy measures were analysed as well. The more attractive measures based on internal rate of return (see Appendix for definition) including carbon offsets were:

The less attractive measures were:

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5.3. Environmental Impact

The Dr. David Suzuki school has an estimated environmental impact, as measured in greenhouse gas production, between 40% and 50% of that for the other energy efficient schools in the comparison presented in this report.

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5.4. Other Non-Energy Benefits

Many of the design features in Dr. David Suzuki school improve the quality of the classrooms and improve the learning experience for the students and the environment for the teachers. These benefits are difficult to quantify financially.

Research has shown that children achieve significantly higher test marks in classrooms that are daylit than in those that are not [1]. Daylighting is one of the best building related investments for the learning environment.

The displacement ventilation system in Suzuki improves air quality because contaminants from room occupants and other sources tend to rise out of the breathing zone rather than being mixed in the space.

A green roof provides an amenity space, a place for fruit, vegetable and flower growth. It increases the roof life span, reduces storm water run off thereby reducing peak loads on sewer systems, filters pollutants and CO2 out of the air and filters pollutants and heavy metals out of rainwater. Green roofs also help to prevent building heat islands.

Storm water retention is not an energy or water saving measure for the building, however it is of societal benefit because it reduces the load on municipal water treatment plants. Vegetation or growing mediums help reduce storm water runoff loads on municipal water treatment. Storm water retention can also improve health of on-site soils, vegetation and habitat areas.

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6. References

 

  1. P. Plympton, J. Brown, and K. Stevens. High-Performance Schools: Affordable Green Design for K-12 Schools. Conference paper presented at the 2004 ACEEE Summer Study on Energy Efficiency in Buildings, August 22-27, 2004.

  2. Windsor Utilities Commission, Monthly Water Rates. Website: < http://www.wuc.on.ca/customerservice/rates.cfm >. Viewed on June 1, 2009.

  3. Grant Thornton LLP, Audit of the Financial Affairs of the City of Windsor and the Windsor Utilities Commission. Report prepared for the Ontario Ministry of Municipal Affairs and Housing. January 2008.

  4. ICF International, Greenhouse Gases and Air Pollutants in the City of Toronto: Toward a Harmonized Strategy for Reducing Emissions. June 2007.

  5. A. Combs, Emission Factors for Greenhouse and Other Gases by Fuel Type: An Inventory. Ad Hoc Committee on Emission Factors. Energy, Mines and Resources Canada. 1990.

  6. David Suzuki Foundation, What is a carbon offset? Website:
    < http://www.davidsuzuki.org/Climate_Change/What_You_Can_Do/carbon_offsets.asp >. Viewed on June 29, 2009.

  7. Planetair. Website: < http://planetair.ca/modules/smartoffset/offset.php >. Viewed on June 24, 2009.

  8. Less. Website: < http://www.less.ca/ >. Viewed on June 24, 2009.

  9. R.S. Means Company Inc., Facilities Maintenance & Repair Cost Data 2009. 2008.

  10. Doug Cane and Jeremy M. Garnet, Update on Maintenance and Service Costs of Commercial Building Ground-Source Heat Pump Systems. ASHRAE Transactions 2000. V.106 Pt. 1. 2000

  11. Danish Wind Industry Association. Website: < http://www.windpower.org/en/tour/econ/oandm.htm >. Viewed on June 24, 2009.

  12. A. Goetzberger and V.U. Hoffman, Photovoltaic Solar Energy Generation. Website:
    <http://books.google.ca/books?id=QF8jDTSByTgC&pg=PA184&lpg=PA184&dq=maintenance+cost+solar+
    pv&source=bl&ots=k5bHDSTjdk&sig=NLpjTPYrNBDaOQdQwkU8mEDxp5Y&hl=en&ei=VXIlSs3hBIbfmQfCo_
    zbBw&sa=X&oi=book_result&ct=result&resnum =5#PPP1,M1
    >. Viewed on June 24, 2009.

  13. Hanscomb Limited, The New Dr. David Suzuki Public School, LEED Construction Design, Windsor, Ontario: Cost Estimate Check. March 16, 2009.

  14. R.S. Means Company Inc., Mechanical Cost Data 2009. 2008.

  15. ICF International., Greenhouse Gases and Air Pollutants in the City of Toronto. June 2007.
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Appendix: Life Cycle Cost Analysis

To evaluate the cost-effectiveness of any of the energy efficiency measures, a calculation must be made to determine if the future net savings (including maintenance and utility costs) for that measure offset the incremental capital cost of the measure. The simplest metric is the "Simple Payback Period", where the incremental capital cost is divided by the annual net savings, resulting in the number of years of operation necessary for the measure to "pay for itself". If the simple payback is less than the life expectancy of the measure, the measure may be considered to be a good investment using this metric.

The calculation of the Simple Payback Period does not take into account the fact that money that is spent on the energy efficiency measure must either be borrowed (for which interest charges will accrue), or must be taken from other potential investments (for which lost opportunity costs should be considered). Either of these costs can be expressed in the form of a "Discount Rate". By applying the Discount Rate on all future cash flows, the "Discounted Payback Period" may be calculated. Again, the measure may be considered to be a good investment if the Discounted Payback Period is less than the expected life expectancy of the measure. To obtain an even more accurate assessment of an investment, an annual escalation rate may be applied to the utility rates used to calculate the savings.

Another useful metric for determining the quality of an investment is the Net Present Value (NPV). To calculate the NPV, all cash flows (initial and future) associated with an investment are added together, with future cash flows "discounted" by the Discount rate. Unlike the Discounted Payback Period, which reveals only when an investment will "pay for itself", the NPV quantifies the absolute (present) value of the investment. Life cycle cost is a commonly used term representing the total discounted expenditures for an investment. It may be used to represent only the outgoing cash flows or the net (incoming and outgoing) cash flows. When used in the latter context, the life cycle cost of a measure relative to that of the base case is just the negative of the NPV over the life of the measure.

Definitions

Discount Rate: The annual interest rate used to evaluate the net present value of future costs and savings. As an investment decision tool, the discount rate represents the minimum acceptable interest rate for an investment. Example: with a 5% discount rate, a projected savings of $105 one year from now has a present value of $100 and a projected savings of $110.25 two years from now has a present value of $100.

Energy Cost Escalation: The compounding increase in energy savings every year. Example: with a 2% escalation rate, and calculated first-year energy savings of $100, the second-year savings would be $102, the third-year savings would be $104.04, etc.

Simple Payback Period (years): the period required for the incremental capital cost to be offset or "paid-back" by the resulting net savings in operating costs, ignoring the discount rate and energy cost escalation. Simple Payback is zero or "immediate" if the incremental capital cost is negative and the annual savings are positive. Simple Payback is undefined if both values are negative. Example: A scenario with an incremental capital cost of $550 provides $100 in annual energy cost savings. The simple payback period would be 5.5 years.

Discounted Payback Period (years): the period required for the incremental capital cost to be offset by the discounted net savings in operating costs. Both the discount rate and energy cost escalation are taken into account.

Internal Rate of Return (or IRR): The annual interest rate for a series of capital expenditures and savings that provides a net present value of zero. As an investment decision tool, the IRR is used to easily compare alternate investments. An IRR less than the discount rate would be considered unacceptable.

Net Present Value (or NPV) Savings: the sum, over the analysis period, of each year's energy cost savings discounted to the present, minus the original capital cost. A positive value for NPV indicates an internal rate of return that is greater than the discount rate; a good investment.
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Greater Essex County District School Board