honorable mention educational facilities ......prior to renovation, the school had a three-year...

A S H R A E J O U R N A L a s h r a e . o r g M AY 2 0 1 74 6

BY ADAM PIERCE, P.E., MEMBER ASHRAE

BUILDING AT A GLANCE

Adam Pierce, P.E., is a principal with CMTA Energy Solutions, a division of CMTA, in Louisville, Ky.

Creating a Contract for Success

HONORABLE MENTIONEDUCATIONAL FACILITIES, EXISTING

A Kentucky school plagued with severe operational and indoor environmental issues paid hundreds of thou-sands of dollars in O&M expenses over 10 years for temporary solutions. The even bigger problem? The school district didn’t have the available capital funding to replace the HVAC system.

Traditional funding revenues were already commit-ted to other school facility debt. So, the school district entered into a guaranteed energy savings contract to fund the new system. Money saved from reduced energy and O&M is reallocated to cover the debt service.

No Budget, No Problem This worst-to-first story began

with a school that had failed

dampers, excessive humidity

levels, and an obsolete building

automation system. It ended

with a renovation and Energy

Star score of 100.

Cox’s Creek Elementary School

Location: Cox’s Creek, Ky.

Owner: Nelson County Board of Education

Principal Use: School building

Includes: 40 rooms including 20 classrooms, cafete-ria, gymnasium, music room, library/media center

Employees/Occupants: 55 staff, 472 students in grades K – 5

Gross Square Footage: 52,833

Conditioned Space Square Footage: 52,833

Substantial Completion/Occupancy: August 1, 2014

Occupancy: 96% asa

National Distinctions/Awards: Energy Star

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2017 ASHRAE TECHNOLOGY AWARD CASE STUDIES35 Years of Excellence

©ASHRAE www.ashrae.org. Used with permission from ASHRAE Journal at www.cmtaegrs.com. This article may not be copied nor distributed in either paper or digital form without ASHRAE’s permission. For more information about ASHRAE, visit www.ashrae.org.

M AY 2 0 1 7 a s h r a e . o r g A S H R A E J O U R N A L 4 7

ABOVE The school is benefiting from an improved indoor learning environment, as well as from significantly reduced operational costs. LEFT Geothermal water source heat pumps serve the building's heating and cooling needs.

Cox's County Elementary School is one of 12 in the

Nelson County School district, located in the heart

of the Bluegrass in Cox’s Creek, Ky. The 52,800 ft2

(4905 m2) facility has approximately 450 students

in grades K – 5 and was constructed in 1991. By 2014,

deficiencies with the existing HVAC system included

failed outdoor air and relief air dampers, an obsolete

building automation system that was not supported,

excessive humidity levels and accompanying issues,

poor thermal comfort, as well as high maintenance

and repair costs.

Guaranteed Energy Savings Contract (GESC)Traditionally in Kentucky, funding school capital

construction projects is accomplished through a com-

bination of state and local tax revenues. Each district’s

capacity to bond building projects is determined by

their uncommitted property tax base. Over the course

of the prior 15 years, Nelson County Schools had made

significant investments in new facilities, and their

property tax revenue had largely been committed to

that debt. There simply was no capacity remaining to

fund an HVAC renovation at Cox’s Creek Elementary

School. The energy and operations and maintenance

cost savings realized as a result of the upgrades pro-

vided the mechanism to fund the annual debt service

Energy EfficiencyPrior to renovation, the school had a three-year

average baseline energy use intensity (EUI) of

58.3 kBtu/ft2·yr (662.1 MJ/m2·yr) (60% electric, 40% pro-

pane). The school’s existing HVAC system was a two-pipe

hot/chilled water unit ventilator system, with a split air-

cooled chiller and propane hot water boiler. At approxi-

mately 23 years old, this system had reached the end of

its useful life, and a major system replacement was nec-

essary to allow effective operation into the future. A new

geothermal heating and cooling system with a dedicated

outdoor air system (DOAS) was selected for the school

because of its low life-cycle cost, energy efficiency, and

ease of maintenance by district personnel. The upgrades

were designed in accordance with ASHRAE Standard

90.1-2013.

The water source heat pumps used were high effi-

ciency two-stage units, which provide part-load efficien-

cies as low as 0.4 kW/ton (0.1 kW/kW) using the 70°F

(21°C) geothermal loop water. The DOAS rooftop units

are equipped with exhaust air heat recovery wheels

to precondition outdoor air prior to supplemental

mechanical heating or cooling. All HVAC controls were

replaced with modern web-based DDC controls. Other

energy-efficient system upgrades include demand con-

trolled ventilation strategies, variable speed pumping,

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Energy Cost

Maintenance Cost

Excess Savings Returned to OwnerSavings to Fund Project

Operations Budget After Improvements

Energy Cost

Maintenance Cost

Operations Budget Before Improvements

FIGURE 1 Operations budget before (left) and after (right) improvements.

payments for the guaranteed

energy savings contract (GESC) the

school board decided to use as an

innovative project delivery method.

The expense is budgeted and paid

for annually out of the operational

budget. Figure 1 illustrates how

guaranteed energy savings pro-

vide alternative funding for much

needed upgrades.

2017 ASHRAE TECHNOLOGY AWARD CASE STUDIES


Per the GESC, a performance guarantee was estab-

lished that quantified energy use reductions at the

facility. Figure 2 illustrates baseline energy conditions,

performance guarantee energy levels, and two full years

of actual post-retrofit energy data.

The baseline period energy use prior to the reno-

vation was 58.3 kBtu/ft2·yr (662.1 MJ/m2·yr), and

the guaranteed performance was 38.4 kBtu/ft2·yr

(436.1 MJ/m2·yr) after renovation. The actual use

is approximately 24 kBtu/ft2·yr (272.6 MJ/m2·yr).

Comparing the baseline period to the post-retrofit

period energy use shows a 60% energy use reduc-

tion, and the performance guarantee metrics have

been greatly exceeded. Labeled in 2015, Cox’s Creek

Elementary School is among only nine schools in

Kentucky that have ever achieved an Energy Star score

of 100.

Indoor Air Quality and Thermal ComfortPrior to renovation, the district was in a crisis situ-

ation regarding the indoor building environment at

Cox’s Creek Elementary School, particularly during

the cooling season. The building's relative humidity

was elevated to the point that condensation had satu-

rated the chilled water piping insulation. Outdoor air

and relief air dampers had failed in numerous loca-

tions, some open and some closed. Photo 1 shows that

the maintenance staff had identified the relief hoods

as a source of infiltration and attempted to seal them

with plastic to prevent outdoor air infiltration at those

locations.

Due to poor control and overcooling in some areas,

chilled water supply temperatures were raised to nearly

60°F (16°C) by the maintenance staff, further com-

pounding the humidity problems. The controls for the

kitchen range hood exhaust fans had been bypassed and

were operating 24/7, causing infiltration of untreated

outdoor air due to negative pressure. Staff members

were complaining of illness, and the community had

become aware that the building had major issues.

The existing two-pipe system was designed with

the ability to provide free cooling via the unit ventila-

tor economizer when the boiler was enabled. Due to

the lack of serviceability of the existing HVAC controls

and damper actuator failures, the free cooling was not

operational, and the outdoor air dampers had been

manually shut. The changeover from heating to cooling

was manual, and the entire building was without any

PHOTO 1 Prior to the renovation, maintenance staff attempted to seal relief hoods with plastic to prevent indoor air infiltration.

Jun Dec Jun Dec Jun Dec MayMo

nthly

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rgy U

se (M

MBt

u)

Baseline Period Post Installation Period600

500

400

300

200

100

0

Monthly Energy Use Baseline Model Performance Guarantee

FIGURE 2 Cox's Creek Elementary School—Energy Savings Verification. Baseline energy conditions, performance guarantee energy levels, and two full years of actual post-retrofit energy data.

geothermal domestic water heating,

and LED exterior lighting.

The local electric utility company

has an “All Electric School” electric

rate structure designed to incentiv-

ize building owners to heat with

electricity in lieu of natural gas or

propane. Because the boiler was

being replaced with a geothermal

well field, the decision was made to

convert remaining equipment and

appliances from propane to elec-

tric. This eliminated the need for

propane in the future and reduced

the electric energy cost per kWh by

approximately 15%.



simultaneous heating and cooling capability. Thermal

comfort was very poor during the spring and fall when

some zones needed heat, while others needed cooling.

During the renovation, all existing outdoor air intake

louvers were infilled. Rooftop relief hoods were removed

with openings sealed and insulated. The DOAS units

were designed to provide precisely controlled and con-

ditioned outdoor air and exhaust air service for the

entire facility. The ventilation rates were calculated in

accordance with ASHRAE Standard 62.1-2013.

Using ASHRAE Standard 55-2013 as the design basis for

the thermal environmental conditions, the geothermal

water source heat pumps provide space heating and air

conditioning. Water source heat pumps are a popular

HVAC system selection in this climate zone due in large

part to the inherent ability of the equipment to simulta-

neously heat and cool various zones, solving one of the

deficiencies of the original two-pipe system.

Additionally, the use of the two-stage water source

heat pumps allows reduced cooling capacities at part-

load conditions, which reduces compressor cycling and

allows better dehumidification at the individual zones

as the cooling coils remain active for longer periods of

time.

Operation and MaintenanceThe district’s O&M costs at Cox’s Creek Elementary

School were escalating year over year and greatly

exceeded the amounts they were spending at their other

similarly sized schools. A historical review of annual

maintenance and repair costs was performed to deter-

mine potential cost savings that could be realized upon

completion of the HVAC renovation. O&M challenges

associated with the existing situation included the

following:

• Daily replacement of ceiling tiles damaged by con-

densation and mold growth;

• Hiring insulation contractors to replace saturated

chilled water pipe insulation;

• Hiring environmental contractors to assess IAQ and

remediate mold growth;

• Hiring environmental contractors to clean unit


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ventilators;

• Reliability and repair costs associated with the

existing chiller;

• Failed attempts at hiring contractors to service ob-

solete controls system; and

• Managing odd return filter size inventory for vari-

ous unit ventilator cabinet sizes.

The system upgrade and selection of the geothermal

water source heat pump system addressed every O&M

challenge the district was facing at that facility. By select-

ing the geothermal system, traditional central plant

equipment such as boilers and cooling towers were

eliminated. Without this equipment the district no longer

incurs the cost of outsourcing maintenance to mechani-

cal service and water treatment contractors. The district

maintenance personnel have familiarity with and the

capability to service water source heat pumps.

By converting from chilled water to geothermal, the

threat of condensation forming on the piping was miti-

gated. The ceiling tile was replaced during the renova-

tion, and there has been no need to replace tiles since.

The space temperature and humidity conditions are

controlled so the potential for mold damage is gone.

The return air filtration is accomplished with 2 ft × 2

ft (610 mm × 610 mm) ceiling-mounted filter grilles

requiring standard 20 in. × 20 in. (508 mm × 508 mm)

filters. The geothermal well field is maintenance free

and can be used again when the system must be reno-

vated during the next HVAC system life cycle.

Figure 3 was developed using the historical cost data

from the district’s accounting system. The trend of base-

line O&M cost escalation between fiscal years 2012 – 2014

conveys the pain the district was feeling as they

attempted to salvage the HVAC system. As can be seen

by the reduction in O&M cost in the two years following

completion of the project, those operational issues have

been addressed as a result of the upgrades.

Cost EffectivenessThe project’s first cost was $1.55 million. By using the

guaranteed cost savings, the school district was able to

replace the aging HVAC infrastructure with modern


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systems with no traditional capital and with no change

to the operating budget.

For a GESC funding mechanism to work, it is essential

that energy and maintenance savings are maximized

while project first cost is minimized. This is a delicate

balancing act that forces the design team to deliver an

exceptionally performing product in the most cost-

effective manner possible. Several design strategies

were implemented to reduce the overall project cost

while maintaining performance. The hydronic piping

throughout the building had been recently re-insulated

by the owner and was reused to serve the new geother-

mal heat pump system. Each heat pump was designed to

serve two adjacent classrooms and operate off averaging

thermostats to reduce equipment and labor cost.

Additionally, the size of the geothermal well field was

able to be reduced by 33% due to exceptional conductivity

performance of its location. These design tactics and others

were able to reduce the overall project cost by approxi-

mately 20%. Ultimately this project delivered a cost-effec-

tive MEP renovation to the owner that also significantly

reduces the annual operating cost of the building.

Environmental ImpactThe environmental impact of this project was an

important consideration during planning. The reduc-

tion in energy use is attributable to the chosen and

implemented energy conservation measures. The

annual energy savings has a direct, quantifiable envi-

ronmental impact. In Kentucky, 93% of electricity is gen-

erated via coal-fired power plants. Thus, the reduction

in energy use corresponds to a large reduction in green-

house gas emissions. This project prevents 177 tons of

CO2 from being emitted into the atmosphere annually.

Overall, it eliminates the need to mine and burn nearly

200,000 lb (90 700 kg) of coal every year.

This has far-reaching implications beyond greenhouse

gas mitigation. Removing the need for coal eliminates

solid fly ash waste, acid mine water pollution, and envi-

ronmental destruction. Every year the school operates,

approximately 72,800 lb (33 000 kg) of coal ash is miti-

gated as a direct consequence of this project. Further,

while more difficult to quantify, not needing to trans-

port 200,000 lb (90 700 kg) of coal from the source to the

utility certainly has a non-negligible positive environ-

mental impact.

The new HVAC system also completely eliminated the

need for propane. Propane accounted for about 40% of

the school’s energy use prior to the project, so the envi-

ronmental impact of eliminating it was significant. This

prevents about 70 tons of CO2 emissions from being

released to the atmosphere annually and removes the

need to transport propane to the school.

Selecting the geothermal ground loop heat exchanger

was an investment for the current HVAC system and for

multiple HVAC system life cycles, as the well field has a

service life expectancy of 50-plus years. This will con-

serve materials and resources during future renovation

projects as well.

ConclusionUsing a guaranteed energy savings contract provided

Cox's Creek Elementary School a way to overcome its

capital funding hurdle. It increased energy efficiency by

60% in a renovated facility and provides a better indoor

learning environment for its students.

$70,587EUI: 58.3

$58,962EUI: 38.5

Baseline Performance Post Installation Post Installation Guarantee Year 1 Year 2

4,0003,5003,0002,5002,0001,5001,000

5000

Annu

al En

ergy

Use

(MM

Btu)

$37,018EUI: 24.1

$36,759EUI: 24.0

FIGURE 3 (Left) Operations and maintenance cost by fiscal year. FIGURE 4 (Right) Baseline energy vs. guaranteed vs. actual data.

$111,940

$158,278

$63,289

$27,051

FY12 FY13 FY14 FY15 – 16

$180,000

$160,000

$140,000

$120,000

$100,000

$80,000

$60,000

$40,000

$20,000

0

O&M

Costs


honorable mention educational facilities ......prior to renovation, the school had a three-year...

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