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Benjamin Banneker Elementary
Michelle Baldwin
Mechanical Option
Architectural Engineering Senior Thesis
Spring 2003
Michelle Baldwin – Mechanical Option 2 Benjamin Banneker Elementary
Abstract
Michelle Baldwin – Mechanical Option 3 Benjamin Banneker Elementary
Table of Contents Topic Page Abstract 2 Executive Summary 4 Background Information 5 Mechanical Redesign 11 Fire Protection 20 Lighting 24 Cost Analysis 26 Conclusions 28 Credits & Acknowledgements 29 Presentation Slides 30 References 31 Appendix 32
Michelle Baldwin – Mechanical Option 4 Benjamin Banneker Elementary
Executive Summary
Benjamin Banneker Elementary is located in Milford Delaware. It is
approximately 64,600 ft2, and the total cost of the project is $8,195,200. The redesign of
the mechanical system featured replacing the existing fan coil units, unit ventilators, and
fin-tub radiators with radiant cooling panels.
Energy recovery ventilation units supply 100% outdoor air to the classroom
spaces. These units contain enthalpy wheels that recovery energy from the exhaust air
stream without mixing the supply and return air. Only the cooling coils in these units
needed to be resized for the new design. The same amount of air, 15 cfm/person, is
supplied in each system. In the new system the energy recovery units must remove the
entire latent load from the outdoor air, and the spaces. As a result the cooling load in
each space is reduced.
To reduce the cost of adding radiant panels to the spaces, the sprinkler piping
was integrated with the radiant panel piping. This integration is allowed by code
because water does not need to travel through any of the panels before it reaches the
sprinkler heads. The control sequence of the valves and pumps guarantees that during
a fire, chilled water flow to the panels is stopped, and water is pumped to the sprinkler
heads from the fire water source.
Adding radiant panels to the classrooms also affected the lighting. Three
different types of lighting layout were analyzed using luxicon. The renderings of the
classroom spaces with the three different fixture types are displayed in the body of the
report. A direct fixture was selected because it supplied the correct amount of light on
the task surface without shadows from the radiant panels.
To compare the systems a first cost analysis and an energy analysis were
performed. The first cost analysis revealed that the radiant panel system first cost was
more expensive than the existing system by approximately $14,000. The energy
analysis resulted in an annual savings of about $4,000 by using the radiant panel
system. Therefore, the payback period is a little over 3 years.
The energy cost savings definitely make the radiant panel system the most
affordable option. It will also be the most comfortable system for the occupants.
Improving comfort in the classroom should be the goal of every school since the ability to
learning is influence by the surroundings.
Michelle Baldwin – Mechanical Option 5 Benjamin Banneker Elementary
Background Information
Benjamin Banneker Elementary School is located in Milford, Delaware, and is
currently under construction. Construction has been underway since January 2002, and
is expected to be complete by mid October of 2003. The project cost is approximately
$8,195,200 and $127 per square foot. This number was taken from the schedule of
values prepared by the architect, R. Calvin Clendaniel Associates.
The school will consist of two floors, the first is 40,600 ft2 and the second is
24,000 ft2 approximately. There will be 28 full size classrooms and 4 smaller
classrooms, an art room, and a music room. The classrooms are laid out in two
symmetrical two-story wings. Each classroom is 800 square feet, and accommodates
30 students. Administrative offices, the nurse’s office, gymnasium, cafeteria, kitchen,
and library are located on the first floor.
The site work of this project is interesting because the school will be built on the
same site as the original Benjamin Banneker Elementary School. During construction
the existing school will remain fully operational until the new school can be occupied. At
that point, the old school will be demolished.
The primary project team includes:
Owner: Milford School District
General Contractor: Conventional Builders Inc.
Architect: R. Calvin Clendaniel Associates
Mechanical Engineering Firm: Furlow Associates
Electrical Engineering Firm: Carew Associates
Structural Engineering Firm: Baker-Ingram Associates
The project manager from Furlow Associates, Vince Cichocki, is my primary contact for
this project. Also, the president of Furlow Associates, Herb Duffield, and the head
mechanical designer, Bob Leitsch will be giving me advice and guidance throughout the
year.
BUILDING ENVELOPE & STRUCTURAL
There are two different typical roof constructions for Benjamin Banneker
Elementary. Type 1 consists of EPDM membrane roofing on 2 1/2” rigid insulation on a
1 1/2” metal deck with steel joists at 30” O.C. Type 2 is a zip rib aluminum standing
Michelle Baldwin – Mechanical Option 6 Benjamin Banneker Elementary
seam roof over 5/8” plywood sheathing on 8” cold formed metal rafters. Type 1 is an R-
15 rated roof, and Type 2 is an R-19 rated assembly. This corresponds to Table B-13
from ASHRAE Std. 90, which lists the minimum R-Values, and maximum U-values for
the building envelope. The walls of Benjamin Banneker are constructed of 8” CMU block
with 1 1/2”rigid insulation and either 4” decorative face block, or metal clad panels on
metal studs at 24” O.C. Both wall types have an R-19 rating and comply with Table B-
13. The floor is an unheated slab on grade with 2” EPS foundation insulation extending
24” horizontally under the slab. The F-factor is 0.70, and this also complies with Table
B-13. A typical window at Benjamin Banneker is operable with aluminum cladding, and
double-glazing and a 1/2” airspace. For this type of window the U-value is 0.48, and the
solar heat gain coefficient is 0.39. The windows make up about 10-20% of the total wall
area. The windows also comply with Table B-13 for a fenestration area of 10.1-20% of
the wall area.
Benjamin Banneker uses a non-composite steel floor system. The longest
typical span is 27’-8”, and the floor-to-floor height is 14’ with a 10’ ceiling height. The
roof consists of steel joists and wide flange girders. The floor slab is a 4” concrete slab
on grade that is thickened under all non-load bearing masonry walls. Footing which
range in size from 3’x3’x1’ to 8’-6”x8’-6”x1’-5” are located under all columns. The
perimeter foundation is a 2’x1’ linear footing.
ELECTRICAL & LIGHTING
The lighting power requirement for Benjamin Banneker is 97500 Watts, and the
building is approximately 64,600 square feet. This corresponds to 1.5 W/ft2, which
complies with ASHRAE Standard 90. The lighting power requirement of a typical school
is 1.5 W/ft2. The classrooms have one 16’ and two 20’ long six lamp direct/indirect 100”
extruded aluminum fluorescent pendant fixtures, with a matte white finish and parabolic
baffles, and are suspended by a cable. The fixtures are 120 V with electronic ballasts.
An existing primary service will supply the school with power. There is a 750
KVA transformer on the secondary side. All of the panels are 208/120 V, 3 phase, 4
wire. There is a 3 pole 70 A emergency generator. Also, there is a 150 A, 3 phase line
for a future building.
Michelle Baldwin – Mechanical Option 7 Benjamin Banneker Elementary
MECHANICAL SYSTEM The primary goal of any mechanical design is to meet the heating, and cooling
loads, and satisfy the ventilation requirements, while also conserving energy, and
minimizing costs. The design cooling load is approximately 273.2 Tons, and the heating
load is 2022 MBH. For Benjamin Banneker Elementary, the ventilation requirements
were 15 cfm/person. The outdoor air conditions for Milford, Delaware are 93°F dry bulb,
76°F wet bulb in the summer, and 14°F dry bulb, 11.3°F wet bulb during the winter.
Benjamin Banneker Elementary uses electricity at a rate of $0.09 per kilowatt-hour, and
the boilers use No. 2 fuel oil at $0.88 per gallon.
The mechanical system consists of one air-cooled chiller, two boilers, and dual
temperature piping. That means the hot water and cold water travel through the same
pipes to the terminal units. There are a variety of terminal units that include unit
ventilators, cabinet unit heaters, fan coil units, and fin-tube radiation devices. There are
also two energy recovery units that use a four-pipe system for the auxiliary heating and
cooling coils. Piping connections are located ahead of the blocking valves, which can be
seen on the flow diagram in figure 1.
Most of the mechanical components operate on a two-pipe system. The main
advantage of this system is that the piping cost in significantly lower than a four-pipe
system. However, the major disadvantage is that the piping must reach equilibrium with
the surrounding air before the system can be changed from the heating to cooling mode,
or vice versa. For a school a two-pipe system is practical because the building will not
be occupied for part of the cooling season. The system will be operating in the heating
mode during most of the school year, and there will only be a few months when the need
for heating and cooling may overlap. However, in the future there is a possibility that the
school system could change to a year round calendar. Then, the current two-pipe
arrangement would not be practical.
There are a total of six rooftop units serving the gymnasium, cafeteria, kitchen,
and administrative area. They are all 100% outdoor air units except the unit that serves
the administrative area. Two units serve the gymnasium, and two units also serve the
kitchen, but one is only used for make-up air, and can be operated manually when
needed. The terminal units such as the unit ventilators and cabinet unit heaters in the
classrooms and other spaces circulate the room air instead of using outdoor air.
The gymnasium and cafeteria require a large amount of ventilation air, but these
spaces are not fully occupied all of the time, so demand controlled ventilation is used.
Michelle Baldwin – Mechanical Option 8 Benjamin Banneker Elementary
CO2 sensors are required to control the ventilation requirements of the space. The
rooftop units will supply 100% outdoor air when it is required.
Benjamin Banneker Elementary uses DDC controls. All of the equipment can be
monitored from an operator’s workstation located in the chief custodian’s office. The
operator will modify the system control sequence from the occupied to the unoccupied
modes. Also, the operator will be notified of any alarms in the system, and will be able
to locate the problem.
During the winter when the outdoor air temperature is below 65°F the boilers will
be on hot standby. The blocking valves on the hot water supply and return piping will be
fully open, and the blocking valves on the chilled water supply and return mains will be
fully closed. Leaving water temperature will be maintained at 180°F.
In the summer when the outdoor air is greater than 70°F the chilled water system
will be activated. The blocking valves on the hot water mains will be fully closed, and the
valves on the chilled water supply and return mains will be fully opened, but if the return
water temperature is above 100°F the chiller blocking valves will remain closed. Leaving
water temperature will be maintained at 44°F.
The energy recovery units use a low velocity, constant volume system. If the unit
cannot maintain the leaving air temperature of 75°F then the auxiliary heating and
cooling coils are used. The heating coil pump will run when the outside air temperature
is less than 50°F, and the cooling coil pump will operate when the temperature is greater
than 75°F.
Michelle Baldwin – Mechanical Option 9 Benjamin Banneker Elementary
FIGURE 1
SY
STE
M F
LOW
DIA
GR
AM
Michelle Baldwin – Mechanical Option 10 Benjamin Banneker Elementary
MECHANICAL SPACE & COSTS The total mechanical floor space is equal to 1645 square feet, and the floor
space lost due to mechanical vertical shaft area is 45 square feet. Only 2.6% of the total
floor area is mechanical space. All of the necessary service clearances and code space
requirements for the mechanical equipment are indicated on the drawings. The
equipment has the appropriate amount of space required by code, but is still packed
tightly into the space.
The total mechanical system cost was $1,182,675 this comes to $18.31 per
square foot approximately. About 15% of the total building cost goes into the
mechanical system, but the equipment only occupies a small portion of the building floor
area. Usually the owner wants to keep the mechanical space to a minimum to gain floor
space. This is difficult because most equipment requires minimum clearances, and
room for maintenance. It is the engineer’s responsibility to minimize the mechanical
space and still comply with the code.
Michelle Baldwin – Mechanical Option 11 Benjamin Banneker Elementary
Mechanical Redesign
BACKGROUND The classroom spaces currently use unit ventilators to heat and cool the spaces
in addition to the supply air. These units can be very noisy and distracting to student’s
learning. They also take up a large amount of floor space in every classroom. The
redesign of the mechanical system of Benjamin Banneker Elementary consisted of
removing the unit ventilators from the classroom spaces and adding radiant panels.
Currently, the classrooms use a dedicated outdoor air system with energy
recovery units. This system will eliminate the latent load and a portion of the sensible
load in the space. Radiant ceiling panels will be used to handle the remainder of the
sensible cooling load. The panels use chilled water to cool the space. This will
eliminate the need for unit ventilators in the classrooms. Without the unit ventilators, the
supply air must dissipate the entire heating load. As a result, reheat must be added to
the supply of every room so that the space is not overcooled in the summer, and the
temperature is comfortable in the winter.
The main advantage of the radiant ceiling panel system is that it will give the
occupants a greater level of comfort. At certain times of the year some spaces may
require cooling while others require heating. Since the school uses a two-pipe system it
is not possible to provide both heating and cooling at the same time. Also it is not
possible to switch between the heating to cooling modes quickly because the piping
must reach equilibrium with the surrounding air before the boiler or chiller can be started.
A dedicated outdoor air system with radiant panels will give the occupants greater
flexibility in the control of room conditions.
NOISE IN THE CLASSROOM Children require different levels of background noise than adults to understand
speech, especially in a classroom setting. Since children’s hearing does not fully
develop until their teens, it is harder for them to distinguish a teacher’s voice clearly over
the background noise of a classroom. Research has shown that in quiet spaces children
and adults can both perceive and understand speech equally well. When the speech is
50% less audible children do not understand everything that is said, but the adults do not
have a problem understanding. At 25% audibility children between the ages of 5 and 7
Michelle Baldwin – Mechanical Option 12 Benjamin Banneker Elementary
can understand almost none of the words, and adults can barely understand all of the
words (Nelson).
HVAC systems are the major source of background noise in classrooms. Many
teachers actually turn off the mechanical equipment while they are teaching which
makes students more uncomfortable in the space and decreases their ability to learn. In
Benjamin Banneker there are unit ventilators in every classroom. The fans in these units
cause a significant amount of background noise.
A new acoustical standard for classrooms (ANSI S12.60-2002) specified that
noise levels should not exceed 35dBA. This is an A-weighted value, which means the
human ear would perceive the noise in the room to be 35dB. The corresponding noise
criterion rating is approximately 30dB. The unit ventilators have a noise criteria rating of
45 dB. This is well over the maximum specified noise levels. By removing the unit
ventilators the space will be quieter and give students a better opportunity to learn.
HUMIDITY CONTROL One of the most common causes of absenteeism in schools is asthma. Poor
indoor air quality and mold are possible causes of asthma, and they can both be affected
by humidity. Humidity also affects performance and learning ability. Children have an
easier time paying attention when they are comfortable. The recommended range of
humidity is 30% to 60% relative humidity according to ASHRAE standard 62. In this
range there is a decrease risk of mold growth, respiratory infections, comfort complaints,
and damage to items such as books and hardwood flooring.
The ventilation rate also affects the learning process. When more outdoor air is
supplied to a space the occupants benefit from increased indoor air quality. For a
school, 15 cfm/person is the minimum amount of ventilation that must be supplied, and it
is the vale that was use in the original and redesign of the system.
DEDICATED OUTDOOR AIR SYSTEMS To achieve the minimum ventilation rate and stay in the recommended relative
humidity range, a Dedicated Outdoor Air System (DOAS) was used. This system
provides 100% outdoor air to the space constantly. The return air is not mixed with the
outdoor air so contaminants are not recirculated through the system. An enthalpy wheel
is used to recover energy from the return air stream. The Greenheck ERT-74H was
used in Benjamin Banneker Elementary and can be seen in Figure 2. The energy
Michelle Baldwin – Mechanical Option 13 Benjamin Banneker Elementary
recovery unit also contains heating and cooling coils which condition the air before it is
supplied to the space.
FIGURE 2 (From www.Greenheck.com)
1. Outdoor air inlet 2. Enthalpy Wheel 3. Cooling and Heating
Coils
REDESIGN CRITERIA To determine the supply air temperature of the spaces I used Carrier’s Hourly
Analysis Program (HAP). It is critical that the dedicated outdoor air unit remove enough
of the humidity from the air to lower the dewpoint temperature. If the dewpoint
temperature is higher than the radiant panel temperature then condensation will form on
the panels.
The original DOAS supplied 75°F air to the space and the dew point temperature
was 58°F. Since the supply temperature was so high, the unit ventilators and fan coil
units dissipated most of the load in the spaces. For radiant panels to function properly in
the space the dew point and supply air temperatures must be lowered. The panels can
only remove sensible load from the space, so the latent load must be removed by the
ventilation system.
For the redesign, the original energy recovery units were not changed. However,
the cooling and heating coils were resized to account for the added capacity. The
supply air temperature was set to 50°F and the resulting space dew point temperature
was 55°F. The total load on the ventilation system was 47.4 tons for the first energy
recovery unit, and 46.6 tons for the second energy recovery unit. This was an increase
from 6.7 tons, and 6.5 tons on the original energy recovery units respectively. The
amount of supply air did not change from the minimum requirement of 15 cfm/person.
Increasing the ventilation rate to 20 cfm/person or greater is a possibility, but it would
require the selection of new energy recovery units that could handle the increased cfm.
Michelle Baldwin – Mechanical Option 14 Benjamin Banneker Elementary
B)
C)
A) FIGURE 3
A) RCU-166 panels showing supply and return connections B) Side profile of RCU-166 radiant panel C) Piping Connections
The next step in the process was to select the type and size the radiant panels. For
Benjamin Banneker Elementary I chose to use RCU-166 radiant panels by Invensys.
These panels are free hanging. The shape of the panels is also interesting because the
edges are curved. This increases the convection over the panel surface and the amount
of air movement in the room without using a fan. In Figure 3 the shape of the panels can
be seen. These panels are available in a wide variety of colors. White is the best option
for Banneker so that the panels blend in architecturally with the drop ceiling. The piping
from the main supply and return pipes are flexible so there will not be any stress in the
piping if the panel is moved. Also, the flexible piping and leak proof snap on couplings
make installation quick and simple. The connection to the chilled water piping is a
water-tight screw on nipple. These connections and hoses can be seen in Figure 3a and
3c. Figure 3b shows a section view of the radiant panel. Chilled water flows through the
copper tube on the top of the panel and cools the panel surface. Natural convection
over the panel surface then cools the room air.
Michelle Baldwin – Mechanical Option 15 Benjamin Banneker Elementary
Cooling Capacity Calculation for REDEC RCU 166 Situation Cooling
Room Air Temperature °F 75.00
Temperature Water Inlet °F 56.00
Temperature Water Outlet °F 59.00
Mean Temperature Difference °F 17.50
Net Cooling Capacity BTUH/ft2 51.10
Asymmetric Load Gain Yes=1; No=0 1
Hot Window Surface Yes=1; No=0 1
Metal Ceiling With 50 % Free Area Yes=1; No=0 -
Total Ceiling Area in ft2 800.00
Module length in inches 48.00
Number of Profiles per Module 6.00
Total RCU Area in ft2 per Module 10.40
Number of Modules 20.00
Total RCU Area in ft2 208.00
Ceiling Coverage in % 26.00
Room Ceiling Height ft 8.50
Asymmetric Load Gain BTUH/ft2 1.49
Hot Window Surface BTUH/ft2 2.48
Correction Factor Ceiling Coverage 1.00
Correction Factor Heights 0.97
Correction Factor Metal Ceiling 1.00
Total Cooling Capacity BTUH/ft2 Active Area 53.41
Total Cooling Capacity BTUH/ft2 Total Ceiling Area 13.89
Total Cooling Capacity BTUH Total Ceiling Area 11,109
Water Flow RCU per Module in US gal/min 0.37
TABLE 1
To size the panels I used the spreadsheet sizer provided by Invensys. Table 1
shows an example of the sizing calculations. For the classrooms, the panel capacity
was 53.41 BTUH/ft2 of panel area. The total number of panels for each room was found
by dividing the total load on the panels by the panel capacity times the panel area.
Tables 2 and 3 contain the final number of panels for each room.
Michelle Baldwin – Mechanical Option 16 Benjamin Banneker Elementary
ZONE #1
ZONE AREA TOTAL
LOAD PANEL LOAD # PANELS PANEL
AREA % CEILING
AREA
TPYE I CLASSROOM A 800 20.2 12.4 22 232.17 29.02
TPYE II CLASSROOM A 800 22.8 13.7 25 256.51 32.06
TPYE III CLASSROOM A 800 20.2 12.4 22 232.17 29.02
TPYE III CLASSROOM A 800 20.2 12.4 22 232.17 29.02
TPYE III CLASSROOM A 800 20.2 12.4 22 232.17 29.02
TPYE IV CLASSROOM A 800 22.8 13.7 25 256.51 32.06
TPYE IV CLASSROOM A 800 22.8 13.7 25 256.51 32.06
GIRLS TR A 250 2.9 0 0 0.00 0.00
BOYS TR A 250 2.9 0 0 0.00 0.00
CORRIDOR A148 1320 8.7 0 0 0.00 0.00
TPYE I CLASSROOM A2 800 22.7 14.7 26 275.23 34.40
TPYE II CLASSROOM A2 800 24.9 15.9 29 297.70 37.21
TPYE III CLASSROOM A2 800 22.7 14.7 26 275.23 34.40
TPYE III CLASSROOM A2 800 22.7 14.7 26 275.23 34.40
TPYE III CLASSROOM A2 800 22.7 14.7 26 275.23 34.40
TPYE IV CLASSROOM A2 800 24.9 15.9 29 297.70 37.21
TPYE IV CLASSROOM A2 800 24.9 15.9 29 297.70 37.21
GIRLS TR B 250 3.6 0 0 0.00 0.00
BOYS TR B 250 3.5 0 0 0.00 0.00
STAFF RESOURCE A200 500 14.2 12.8 23 239.66 47.93
SELF-CONTAINED A230 404 9.8 2 4 37.45 9.27
SELF-CONTAINED A230 404 9.8 2 4 37.45 9.27
BASIC SKILLS A229 384 8.3 6.3 11 117.96 30.72
SPEECH A228 384 6.6 3.5 6 65.53 17.07
MUSIC A207 748 14 4.2 8 78.64 10.51
OFFICE SECOND FLOOR 80 1.4 0.8 1 13.75 17.19
OFFICE SECOND FLOOR 80 1.4 0.8 1 13.75 17.19
OFFICE SECOND FLOOR 80 1.4 0.8 1 13.75 17.19
OFFICE SECOND FLOOR 80 1.4 0.8 1 13.75 17.19
CORRIDOR A234 1320 12.7 5.8 10 108.59 8.23
TOTAL 426 TABLE 2
To prevent condensation, the panel inlet temperature will be 56°F, which is
higher than the space dewpoint temperature. The flow rate of water through the panels
is 0.37 gpm and the pressure drop is 1.4 psi. Two panels can be piped in series and the
outlet water temperature is 59°F. The panels will not add a significant amount of weight
to the structure. Each panel weighs approximately 1.5 lb/ft2 of panel area. The
classrooms have an average of 25 panels each, and each panel is 10.4 ft2, so the total
weight added would be 390 lbs. The structural system should be design with a safety
factor to cover well over that amount of load.
Michelle Baldwin – Mechanical Option 17 Benjamin Banneker Elementary
ZONE #2
ZONE AREA TOTAL
LOAD PANEL LOAD # PANELS PANEL
AREA % CEILING
AREA
TPYE I CLASSROOM B 800 20.2 12.4 22 232.17 29.02
TPYE I CLASSROOM B2 800 22.7 14.7 26 275.23 34.40
TPYE II CLASSROOM B 800 22.8 13.7 25 256.51 32.06
TPYE II CLASSROOM B2 800 24.9 15.9 29 297.70 37.21
TPYE III CLASSROOM B 800 20.2 12.4 22 232.17 29.02
TPYE III CLASSROOM B 800 20.2 12.4 22 232.17 29.02
TPYE IV CLASSROOM B 800 22.8 13.7 25 256.51 32.06
TPYE IV CLASSROOM B 800 22.8 13.7 25 256.51 32.06
TPYE IV CLASSROOM B 800 22.8 13.7 25 256.51 32.06
TPYE IV CLASSROOM B2 800 24.9 15.9 29 297.70 37.21
TPYE IV CLASSROOM B2 800 24.9 15.9 29 297.70 37.21
TPYE IV CLASSROOM B2 800 24.9 15.9 29 297.70 37.21
STORAGE A132 120 0.8 0 0 0.00 0.00
EQUIPMENT A133 140 2.5 0.3 1 5.62 4.01
LIBRARY A135 1170 22.9 6.5 12 121.70 10.40
WORKROOM A136 140 0.9 0 0 0.00 0.00
STORAGE A137 85 0.6 0 0 0.00 0.00
STORAGE A139 140 0.9 0 0 0.00 0.00
MULTIMEDIA A138 240 4.9 0.4 1 7.49 3.12
CORRIDOR A123 1320 8.7 0.9 2 16.85 1.28
CORRIDOR A163 250 1.7 0.9 2 16.85 6.74
ACAD TALENTED A227 384 7.4 4.4 8 82.38 21.45
ART A208 972 23 14 25 262.12 26.97
CORRIDOR A218 1320 12.7 5.1 9 95.49 7.23
BOYS TR A 250 2.9 0 0 0.00 0.00
BOYS TR B 250 3.5 0 0 0.00 0.00
GIRLS TR A 250 2.9 0 0 0.00 0.00
GIRLS TR B 250 3.6 0 0 0.00 0.00
TPYE III CLASSROOM B2 800 22.7 14.7 26 275.23 34.40
TPYE III CLASSROOM B2 800 22.7 14.7 26 275.23 34.40
TOTAL 418 TABLE 3
Since the spaces are not occupied all of the time, overcooling is a concern.
Reheat coils were added to the supply air streams of every room. The load at the peak
heating condition is displayed in Tables 4 and 5. The piping connection for the heating
coils must be located before the blocking valves of the dual temperature piping system.
Michelle Baldwin – Mechanical Option 18 Benjamin Banneker Elementary
HEATING COIL SIZING DATA - ZONE #2
Room Name Coil Load (MBH)
Coil Ent/Lvg DB
(°F)
Water Flow @20.0 °F
(gpm) TPYE I
CLASSROOM B 21.8 54.8 / 74.2 2.18 TPYE I
CLASSROOM B2 24.5 56.6 / 76.0 2.45 TPYE II
CLASSROOM B 21.9 56.6 / 74.0 2.2 TPYE II
CLASSROOM B2 24.4 57.8 / 75.4 2.44 TPYE III
CLASSROOM B 21.8 54.8 / 74.2 2.18 TPYE III
CLASSROOM B 21.8 54.8 / 74.2 2.18 TPYE IV
CLASSROOM B 21.9 56.6 / 74.0 2.2 TPYE IV
CLASSROOM B 21.9 56.6 / 74.0 2.2 TPYE IV
CLASSROOM B 21.9 56.6 / 74.0 2.2 TPYE IV
CLASSROOM B2 24.4 57.8 / 75.4 2.44 TPYE IV
CLASSROOM B2 24.4 57.8 / 75.4 2.44 TPYE IV
CLASSROOM B2 24.4 57.8 / 75.4 2.44
STORAGE A132 1.9 26.9 / 70.0 0.19
EQUIPMENT A133 3.8 42.7 / 70.0 0.38
LIBRARY A135 35.3 47.6 / 75.3 3.54
WORKROOM A136 1.9 33.0 / 70.0 0.19
STORAGE A137 1.9 9.3 / 70.0 0.19
STORAGE A139 1.9 33.0 / 70.0 0.19
MULTIMEDIA A138 7.6 42.3 / 70.0 0.76
CORRIDOR A123 13.3 42.6 / 70.0 1.33
CORRIDOR A163 1.9 60.0 / 70.0 0.19 ACAD TALENTED
A227 6.9 56.3 / 73.0 0.69
ART A208 24.8 56.6 / 76.0 2.48
CORRIDOR A218 17.5 51.1 / 76.0 1.76
BOYS TR A 12.8 -7.5 / 72.7 1.28
BOYS TR B 13.7 7.2 / 76.8 1.37
GIRLS TR A 13 -6.7 / 74.1 1.3
GIRLS TR B 13.6 8.6 / 76.4 1.36 TPYE III
CLASSROOM B2 24.5 56.6 / 76.0 2.45 TPYE III
CLASSROOM B2 24.5 56.6 / 76.0 2.45
TABLE 5
TABLE 4
HEATING COIL SIZING DATA - ZONE #1
Room Name Coil Load (MBH)
Coil Ent/Lvg DB
(°F)
Water Flow @20.0 °F
(gpm) TPYE I
CLASSROOM A 21.8 54.8 / 74.2 2.18 TPYE II
CLASSROOM A 21.9 56.6 / 74.0 2.2 TPYE III
CLASSROOM A 21.8 54.8 / 74.2 2.18 TPYE III
CLASSROOM A 21.8 54.8 / 74.2 2.18 TPYE III
CLASSROOM A 21.8 54.8 / 74.2 2.18 TPYE IV
CLASSROOM A 21.9 56.6 / 74.0 2.2 TPYE IV
CLASSROOM A 21.9 56.6 / 74.0 2.2
GIRLS TR A 13 -6.7/74.1 1.3
BOYS TR A 12.8 -7.5/72.7 1.28
CORRIDOR A148 26.6 15.2 / 70.0 2.66 TPYE I
CLASSROOM A2 24.5 56.6 / 76.0 2.45 TPYE II
CLASSROOM A2 24.4 57.8 / 75.4 2.44 TPYE III
CLASSROOM A2 24.5 56.6 / 76.0 2.45 TPYE III
CLASSROOM A2 24.5 56.6 / 76.0 2.45 TPYE III
CLASSROOM A2 24.5 56.6 / 76.0 2.45 TPYE IV
CLASSROOM A2 24.4 57.8 / 75.4 2.44 TPYE IV
CLASSROOM A2 24.4 57.8 / 75.4 2.44
GIRLS TR B 13.6 8.6 / 76.4 1.36
BOYS TR B 13.7 7.2 / 76.8 1.37 STAFF
RESOURCE A200 11 64.9 / 73.8 1.1 SELF-CONTAINED
A230 16.1 45.5 / 75.2 1.61 SELF-CONTAINED
A230 16.1 45.5 / 75.2 1.61 BASIC SKILLS
A229 7.4 60.4 / 72.8 0.74
SPEECH A228 6.9 54.2 / 73.0 0.69
MUSIC A207 19.8 47.9 / 73.4 1.98 OFFICE SECOND
FLOOR 1.4 55.6 / 73.0 0.14 OFFICE SECOND
FLOOR 1.4 55.6 / 73.0 0.14 OFFICE SECOND
FLOOR 1.4 55.6 / 73.0 0.14 OFFICE SECOND
FLOOR 1.4 55.6 / 73.0 0.14
CORRIDOR A234 17 55.2 / 73.9 1.7
Michelle Baldwin – Mechanical Option 19 Benjamin Banneker Elementary
CONTROLS The controls for the system are relatively simple because they are just based on
thermostat control. When the space is too cold and the thermostat level is raised the
reheat coil is used to raise the temperature of the supply air. When the space does not
require additional cooling bye the radiant panels, valves on the radiant panel piping will
reduce or stop the flow of chilled water from the panels.
Since the windows in the classrooms are operable there is a risk of condensation
formation if the windows are open. The windows could be connected to a sensor that
would indicate when a window is open. Another sensor would then measure the outdoor
dewpoint and compare it to the design dewpoint. If there is more humidity in the air than
in the space the panels need to be turned off. If the outdoor humidity is lower than the
space humidity then the open windows will not affect the panels, and the load on the
system would be reduced. The other option to solve this condensation issue would be to
replace the windows with inoperable windows.
Michelle Baldwin – Mechanical Option 20 Benjamin Banneker Elementary
Fire Protection INTEGRATION OF SPRINKLER AND RADIANT PANEL PIPING To reduce the cost of chilled water piping for the radiant panels, the panel piping
was integrated with the existing sprinkler piping. The flow diagram in Figure 4 shows the
piping and radiant panel layout. The red arrows indicate the direction water during a fire
when the sprinklers would be on. The blue arrows indicate the chilled water flow during
normal operation of the radiant panels.
FIGURE 4 (Mumma) Since the chilled water temperature is above the dewpoint temperature of the
spaces, most of the piping does not need to be insulated. The piping must only be
insulated from the chiller up to pump P2 because the chilled water does not reach the
supply temperature until that point. By integrating the radiant panel piping with the
Michelle Baldwin – Mechanical Option 21 Benjamin Banneker Elementary
sprinkler piping money is saved, but there is still an added piping cost because a chilled
water return line must be installed.
RADIANT PANEL CONTROL Valve V2 is used to control the supply temperature of the chilled water by
allowing cold water from the chiller to enter the recirculated water. Pump P2 is a
variable speed pump and it modulates to maintain a pressure differential between the
supply and return of the radiant panels. Valve V3 regulates the amount of water flowing
through a radiant panel group. The space thermostat controls this valve. Condensation
prevention can be accomplished in two ways. First, pump P2 could be regulated based
on the space dewpoint temperature. If the space dewpoint is not below the chilled water
supply temperature then the pump will not run. Second, valve V2 could be adjusted so
that it supplies water at a temperature always above the measured space dewpoint
temperature. (Mumma)
FIRE PROTECTION SYSTEM CONTROL During normal operation pump P4 is used to maintain a fixed amount of water in
the compression tank. The fire pumps P3 are used to maintain the system
pressurization. When a fire occurs and the sprinkler heads open the compression tank
will begin to feed the system. The alarm valve is then set off by the large volume of flow,
and consequently pumps P1 and P2 and the chiller are stopped. Valves V4 and V5 are
also closed to stop all water flow to and from the chiller. The pressure in the system will
then drop and pump P3 is started. This causes the flow in the radiant panel return
piping to be reversed. The radiant panel supply piping is also supplied by the fire pumps
through the check valves on each floor. The system meets fire protection code
requirements because the water does not need to pass through the radiant panels
before it reaches the sprinkler heads. (Mumma)
Michelle Baldwin – Mechanical Option 22 Benjamin Banneker Elementary
Lighting LIGHTING LAYOUT AND FIXTURES The current lighting design for the classrooms features indirect/direct 100”
extruded aluminum fluorescent fixtures. They have parabolic baffles, are suspended by
cables, and have 120V electronic ballasts. Every classroom has three fixtures. Two of
the fixtures are twenty feet long with ten lamps, and the remaining fixture is sixteen feet
long with eight lamps. Using luxicon I modeled three lighting and radiant panel layouts
to determine if the layout provided an adequate amount of light on the task surface.
To model the lights, photometry information was obtained from
www.lightolier.com. According to the IESNA Lighting Handbook, classrooms are rated
as a category D. This means that the lighting requirement for the task surface is 30 fc
(foot candles). From ASHRAE standard 90, the guideline for the number of watts per
square foot is 1.5 W/ft2. The IESNA Lighting Handbook was also used to determine the
light loss factor for each light fixture.
FIGURE 5 (A)
Michelle Baldwin – Mechanical Option 23 Benjamin Banneker Elementary
FIGURE 5 (B) Figure 5 is a rendering of the original lighting with the radiant panels. This layout
produced a light level of 48.6 fc, and 1.07 W/ft2. This fixture does supply enough light to
the surface, but the indirect portion of the lighting is not necessary because the radiant
panels block most of the reflection from the ceiling.
The second type of lighting fixture that I tested was a 2’ by 4’ recessed fixture
that was an alternate for the project. Using nine fixtures, the light level produced was
45.6 fc and 0.89 W/ft2. This fixture also provides enough light over the task area, but
since the panels are directly under the fixture in some places, shadows are cast in
certain areas, and can be seen in Figure 6.
The third fixture I tested was a direct hanging fixture with parabolic baffles. Each
fixture has two lamps, and the same number of fixtures was used as the original design.
This layout produced a lighting level of 40.1 fc, and 1.31 W/ft2. This configuration also
produces an adequate amount of light on the task surface level, but the number of watts
per square foot is higher. Figure 7 shows the rendering of this lighting fixture and the
radiant panels.
For the classrooms I would suggest using the direct hanging fixture because it
produces light levels that are the closest to the required amount of 30 fc. The other
fixtures have higher light levels that could produce glare on the task surface, or shadows
from the radiant panels. It also might be possible to find another fixture that produces a
Michelle Baldwin – Mechanical Option 24 Benjamin Banneker Elementary
lower number of watts per square foot, but the fixtures used are good examples of each
type of fixture.
FIGURE 6 (A)
FIGURE 6 (B)
Michelle Baldwin – Mechanical Option 25 Benjamin Banneker Elementary
FIGURE 7 (A)
FIGURE 7 (B)
Michelle Baldwin – Mechanical Option 26 Benjamin Banneker Elementary
Cost Analysis
FIRST COST To compare the relative first cost of the radiant panel system and the unit
ventilator system, I used R.S. Means. The total cost of the project was $8,195,200, and
the mechanical system was $1,182,675. That is approximately 15% of the total building
cost. Table 6 summarizes the amount of equipment subtracted and added to the
system. The total cost of the equipment not used in the original system was $159,694.
The additional cost of the radiant panel system equipment was $158,919, resulting in a
total mechanical system cost of $1,181,900. The decrease in first cost is only 0.06% of
the original cost so the first cost would not be the deciding factor between the two
system options.
Equipment Removed
Unit
Ventilators Fin-Tube Radiators
Fan-Coil Units
Condensate Piping
Cost/Unit $3,975 $345 $1,625 $12
Units 28 8 24 567
Total $111,300 $2,760 $39,000 $6,634
Equipment Added
Radiant Panels Piping
Reheat Coils Valves
Check Valves
Other Valves Pump Pump
Cost/Unit $135 $16 $350 $49 $570 $400 $600 $300
Units 844 692 60 422 6 6 1 1
Total $114,109 $11,210 $21,000 $20,678 $3,420 $2,400 $600 $300
Mechanical Cost $1,182,675.00
Minus $159,694.00
Plus $173,717.20
Total $1,196,698.20
Additional Cost $14,023.20
TABLE 5
Michelle Baldwin – Mechanical Option 27 Benjamin Banneker Elementary
ENERGY ANALYSIS Energy analysis is another tool the owner could use to decide between the
systems. However, it is not commonly used by engineers because it is time consuming.
Energy analyses of the existing system and the redesigned system were performed.
Table 7 shows the energy analysis for both systems. The results showed that the cost
to maintain the original system is $69,414 annually, and the cost for the redesigned
Initial School Final School
Component ($) Component ($)
Air System Fans 15,883 Air System Fans 10,202
Cooling 15,668 Cooling 15,122
Heating 1,495 Heating 2,586
Pumps 1,303 Pumps 2,318
Cooling Tower Fans 0 Cooling Tower Fans 0
HVAC Sub-Total 34,349 HVAC Sub-Total 30,227
Lights 20,490 Lights 20,490
Electric Equipment 14,575 Electric Equipment 14,575
Misc. Electric 0 Misc. Electric 0
Misc. Fuel Use 0 Misc. Fuel Use 0
Non-HVAC Sub-Total 35,065 Non-HVAC Sub-Total 35,065
Grand Total 69,414 Grand Total 65,292 TABLE 7
system is $65,292 annually. It would be approximately $4,122 more expensive per year
to use the original system. To an owner this would be the deciding factor over which
system to select. However, the redesigned system also has many advantages that
cannot be measured with a dollar amount. First of all comfort is greatly improved by
using the radiant panel system. Noise from the fans of the unit ventilators is eliminated.
Classrooms will also be more comfortable because they do not rely on the two-pipe
system. The spaces can easily be changed from the heating to cooling mode or vice
versa without a lag period for the entire system to be changed from heating to cooling.
Also, by removing the unit ventilators in the classrooms more floor area is gained.
These factors should all be considered when selecting the mechanical system.
Michelle Baldwin – Mechanical Option 28 Benjamin Banneker Elementary
Conclusions SYSTEM REDESIGN
Replaced existing unit ventilators, fan coil units, and fin-tube radiators with
radiant cooling panels.
Resized cooling coils of the Energy Recovery Units.
Added heating coils to the supply air streams of every space analyzed.
Integrated the sprinkler piping with the radiant panel piping.
Redesigned the classroom lighting layout.
ADVANTAGES Reduced classroom background noise.
Increased the usable floor area.
Increased the comfort and operating flexibility of the mechanical system.
Annual energy savings.
Short payback period.
DISADVANTAGES Increased level of controls.
Increased first cost.
RECOMMENDATIONS In this analysis I have completed all of the goals that I wanted to achieve with the
redesigned system which included:
The original energy recovery units were used by only resizing the cooling
coil. The dew point in the space is maintained at a level lower than the
radiant panel inlet water temperature so that condensation is not a
problem. The sprinkler piping was successfully integrated with the radiant
panel piping. A lighting layout was selected that provided an adequate
amount of light on the task surface. Finally, Background noise was
reduced by removing the unit ventilators in the classrooms.
After analyzing the original system and the redesigned system I believe that the DOAS
with radiant cooling would be beneficial since it would greatly increase comfort. Comfort
is a factor that influences a child’s learning ability, and the value of learning is priceless.
The most significant reason to use the radiant panel system in Benjamin Banneker
Elementary is that the annual energy costs are decreased by $55,277, which would be
the most important factor to the owner.
Michelle Baldwin – Mechanical Option 29 Benjamin Banneker Elementary
Credit & Acknowledgements
I would like to thanks everyone who donated their time to answer my
questions, provide support, and help me throughout the semester, especially:
Primary Mechanical Consultant: Dr. Stanley Mumma Furlow Associates: Herbert Duffield
Vince Cichocki Bob Leitsch
Fellow AE Students: Jaclyn Ambrocik
Rebecca Ho Jason Reece Rebecca Rubert Megan Hawk
Also special thanks to my Friends & Family
Michelle Baldwin – Mechanical Option 30 Benjamin Banneker Elementary
References
ASHRAE Standard 62 ASHRAE Standard 90 Darbeau, Michele. “ARI’s Views on ANSI S12.60-2002.” ASHRAE Journal February
2003. “Humidity Control in School Facilities.” ASHRAE Journal 2003. The IESNA Lighting Handbook, Reference & Application. 9th Edition. Illuminating
Engineering Society of North America. Marks, Rea, Ph.D, FIES. 2000. Mumma, Ph.D., P.E., Stanely A. & Christopher L. Conroy. “Ceiling Radiant Cooling Panels
As A Viable Distributed Parallel Sensible Cooling Technology Integrated With Dedicated Outdoor-Air Systems.” ASHRAE Transactions 2001, Vol. 107 Pt. 1
Mumma, Ph.D., P.E., Stanley A. “Chilled Ceilings in Parallel with Dedicated Outdoor Air
Systems: Addressing the Concerns of Condensation, Capacity, and Cost.” ASHRAE Transactions 2002, Vol. 108 Pt. 2
Mumma, Ph.D., P.E., Stanely A. & Walter M. Janus, P.E. “Integration of Hydronic Thermal
Transport Systems with Fire Suppression Systems.” ASHRAE Transactions 2001, Vol. 107 Pt. 1
Nelson, Peggy B. “Sound in the Classroom, Why Children Need Quiet.” ASHRAE
Journal February 2003. Schaffer, P.E., Mark E. “ANSI Standard: Complying With Background Noise Limits.”
ASHRAE Journal February 2003. Energy Recovery Ventilators. “http://www.greenheck.com.” Energy Recovery
Ventilators with Heating and Cooling Coils - model ERT. Invensys Radiant HVAC Products. “http://www.redec.com/hvac.htm.” “R.S. Means, Mechanical Cost Data.” 2003.
Michelle Baldwin – Mechanical Option 31 Benjamin Banneker Elementary
Appendix HAP Calculations – Original Design A1 HAP Calculations – Redesign A2 Energy Analysis – Original Design A3 Energy Analysis – Redesign A4 Radiant Panel Selection Spreadsheet A5 Radiant Panel Specs A6 Energy Recovery Units Specs A7 Lighting Specs A8 Lighting – Layout A9 Lighting – Rendering A10 Flow Diagrams A11 Cooling Coil Selection A12 Heating Coil Selection A13 Cost Analysis A14
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