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Southeast HVAC News
Green HVAC Design Helps
School District Cut Utility Costs by 35% in New 30% Larger H.S.
Clark County (Kentucky) school's innovative hybrid HVAC design using
geothermal, chilled beams, heat recovery and other technologies.
 The
new $60-million George Rogers Clark High School's (GRCHS) green
design is helping record up to 35-percent less monthly utility costs
while providing better indoor air quality and comfort than the
30-percent smaller conventional building it replaced.
One reason for the increased
efficiency is a hybrid HVAC design featuring a geothermal well field
that supplies active chilled beams, dual wheel outdoor air
dehumidification systems and other cutting-edge technologies,
according to Paul Christy, superintendent, Clark County Public
Schools. Christy, the county schools' former director of operations,
oversaw the 300,000-square-foot high school's HVAC design team that
included engineer, Charles H. Wade, P.E., LEED AP, vice president,
KTA Engineers, Lexington, Ky; Mark Saunier, B.S.E.E., LEED AP, CEM
and president of energy company, Comfort & Process Solutions,
Lexington; and engineers from SEMCO, a Columbia, Mo.-based
manufacturer of chilled beams and heat recovery outdoor air
equipment. D.W. Wilburn Construction Co., Somerset, Ky, oversaw the
construction and HVAC installation.
Originally specified as a conventional
200-foot, 80-well geothermal field with just GSHPs, Christy opted
for enhancing the design by replacing the proposed 350 heat pumps
with 542 active chilled beams and six SEMCO Pinnacle Series
dedicated outdoor air (DOAS) heat recovery systems. Christy's
decision was based on visiting a similar system at Greenville,
S.C.-based Furman University and reviewing an 18-page building
energy simulation report prepared by SEMCO.
The report, which was completed by
using the Carrier hourly analysis program (HAP) in conjunction with
SEMCO's supplemental Pinnacle hourly energy analysis module,
compared the estimated annual energy consumption of the high
school's three most-likely HVAC approaches:
1) a DX-based outdoor air
system, including a total energy recovery wheel and hot gas reheat
capabilities preconditioning the outdoor air delivered directly to
the classroom spaces served by individual GSHPs.
2) a dedicated outdoor air
system (DOAS) incorporating both energy recovery and passive
dehumidification wheels, served by a ground source heat pump to
precondition outdoor air delivered directly to the classroom spaces
served by individual GSHPs.
3) a DOAS and active chilled
beams combination, all served by a GSHP chiller to condition the
media center and all classrooms.
Based on an electric rate of $.07/Kwh,
the estimated annual HVAC energy cost for each of the three systems
was 1) $73,490 ($.53/square foot); 2) $56,670 ($.41/square foot);
and 3) $45,175 or ($.33/square foot), respectively. Some of the
greatest efficiency is attributed to a 50-percent air flow reduction
that chilled beam technology offers versus conventional forced air
distribution methods.
"The (GRCHS) mechanical system was
installed for $19.5 per square foot, which is the same or less than
water source heat pumps or VRV ground source systems currently in
Kentucky," said Saunier, whose company offers building automation,
HVAC service and energy efficiency products.
The old, 199,492-square-foot
circa-1960's high school building, a four-pipe boiler/chiller system
with fan coil units, was averaging annual utility costs of
approximately $194,040 ($.97/square foot). "In the first four months
of operation, the new building's preliminary utility bill figures
were $41,800 less than our old building during the same period,"
said Christy, who oversees 11 county schools.
The savings comes primarily from
better humidity control and subsequently higher set point
temperatures with no trade-off of indoor air comfort. The system's
comparably lower 43°F dew point temperature allows for greatly
reduced air volume due to the superior humidity control from
dual-wheel dehumidifiers that control both latent and sensible
humidity, according to Saunier, who helped convert the original
design from conventional heat pumps to Christy's requested chilled
beam concept.
Other Clark County schools with
conventional HVAC systems typically operate at 70°F amidst
occasional "too warm" complaints in spring, summer and fall. GRCHS's
temperature complaints have been few due to better humidity control,
even though set points average five degrees warmer at 75°F. "We've
had to educate teachers that set point classroom temperatures they
may have previously perceived as being too warm, are now a more
comfortable temperature due to this building's superior humidity
control," Christy said.
The IQHC chilled beams, which are
supplied by a water-to-water GSHP by ClimaCool, Oklahoma City,
Okla., have a 12-slot nozzle that's field-adjustable for areas with
excessive solar gain or heat loss. CPS service department is
training the GRCHS maintenance staff to adjust volume and up to a
45-degree angle directional airflow for hotspots with each chilled
beams' easily-accessed hand-operated levers for the greatest air
flow flexibility efficiency. The nozzle adjustment additionally
provides a unilateral, disproportional or equal air volume from each
side. It allows ideal room coverage and flexible distribution
possibilities without relocating the device.
The chilled beams never develop
condensation because five rooftop DOAS units ranging from 3,700 to
14,500-cfm supply them with semi-neutral, super dry air. There is
one 7,000-cfm DOAS that resides in a mechanical room. Some areas
with high ceilings that aren't ideal for chilled beams, such as the
cafeteria and gym, use their own DOAS to distribute cooling and
heating via the GSHP loop.
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The DOAS units
feature variable frequency drives (VFD), integrated GSHPs and
dew point discharge control that are all interfaced with the
school's building automation system by, Delta Controls, Surrey,
B.C. The control system runs through each DOAS unit's wintertime
supply temperature control stages that use the enthalpy wheels'
heat recovery to minimize the onboard mechanical heat pump's
runtimes. The system also saves energy by maintaining humidity
with a recirculation mode during unoccupied periods, which
lessens ramp up time heating or cooling when the school opens
each day.
Besides energy
savings, GRCHS also received the following benefits from the HVAC
system:
• saved
2,000-square-feet of storage space that would have been consumed by
heat pumps in two mechanical rooms that are now used for storage and
other uses;
• reduced maintenance
because chilled beams require no filters and moving parts, thus
eliminating any periodic classroom interrupting maintenance tasks;
• less piping because
only two of every classroom's four chilled beams were four-piped.
Additionally, chilled beam piping diameters are considerably smaller
than the original configuration of piping heat pumps to each
classroom;
• reduced ductwork
because chilled beams require only six-inch-supply take-offs and
half the air volume of a traditional system;
• quieter classroom
environments because chilled beams are approximately 10 to 15-db
quieter than heat pumps;
• better temperature
and humidity control by independently controlling each load;
"We like the idea of
constant air movement at low velocities from a comfort and a noise
perspective," said Ron Murrell Jr., AIA, LEED AP, principal at
Rosstarrant Architects, Lexington, an architect firm that designs
educational facilities exclusively. Chilled beams provide a quieter
learning atmosphere as opposed to the considerably noisier method of
mechanical units cycling on and off in or near the classroom."
"When we told a state
education representative that our outdoor air system wouldn't shut
off because it actually drives the chilled beams, he was excited
because some conventional Kentucky school buildings suffer poor IAQ
when school operators shut off outdoor air to eliminate high indoor
humidity," said Saunier.
The building qualifies
on the energy requirements for LEED platinum certification, however
the school district chose to instead use the application money for
educational programs, according to Saunier.
Besides the HVAC, the
building design also contributes greatly to energy efficiency.
Rosstarrant designed the facility with a variety of efficient
techniques and materials, such as orienting the rectangular,
three-story building to its site by exposing the long axis to the
north and partially integrating the south side into a steep grade
the plat offered naturally.
• windows are
one-inch, insulated glazing with a low-E coating by Guardian, Auburn
Hills, Mich.;
• an aluminum sun
shade by Peachtree Protective Covers, Hiram, Ga., shields exterior
windows from solar heat gain;
• building envelope
features a closed cell spray polyurethane foam insulation
manufactured by BASF, Houston, Texas, in the load-bearing cavity
masonry wall construction;
• The roof consists of
light insulated concrete by Siplast, Irving, Texas, and white PVC
cool roof membrane by Sika Sarnafil, Canton, Mass;
• T-5 fluorescent
lighting throughout and 148 tubular solar lights in the top floor
classrooms help cut utility bills;
Christy also boasts of
.53-percent student attendance increases the first five months of
operation in the 2013 Fall Semester versus the same period the
previous year, which he attributed partially to superior indoor air
quality (IAQ) and humidity control.
The success of the project has led the school district's design team
to consider chilled beams and DOAS in an upcoming school retrofit.
"Because of space restrictions in a retrofit, we see chilled beams
as a space-saving and an air comfort solution," said Christy.
About SEMCO: Since its founding in 1963 as a sheet metal
fabrication company with five employees, SEMCO has built a
reputation as a worldwide product innovator in the science of air
movement, noise abatement, energy efficiency and indoor air quality
with more than 300 employees and more than 300 manufacturer's
representatives. Major product lines include spiral metal HVAC duct,
energy recovery equipment, chilled beams, and acoustics equipment.
SEMCO is a Fläktwoods company based in Columbia, Mo. SEMCO operates
three manufacturing facilities in Morrilton, Ark., Petit Jean, Ark.,
and Roanoke, Va. SEMCO also operates an ASHRAE 84-compliant research
and development facility dedicated to the innovation of new products
for the 21st Century and beyond. For more information, please visit
www.SEMCOhvac.com;
email
sales.SEMCO@flaktwoods.com; or call 1-888-473-6264.
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