Benjamin Banneker Elementary thesis report … · Michelle Baldwin – Mechanical Option 8 Benjamin Banneker Elementary CO 2 sensors are required to control the ventilation requirements

Benjamin Banneker Elementary

Michelle Baldwin

Mechanical Option

Architectural Engineering Senior Thesis

Spring 2003

Michelle Baldwin – Mechanical Option 2 Benjamin Banneker Elementary

Abstract


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


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.


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


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.


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.


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.


FIGURE 1

SY

STE

M F

LOW

DIA

GR

AM


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.


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


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


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.


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.


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.


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 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 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




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.


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 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.


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 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 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 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

CORRIDOR A234 17 55.2 / 73.9 1.7


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.


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


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)


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)


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


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)


FIGURE 7 (A)

FIGURE 7 (B)


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


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.


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.


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


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.


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

Documents

Benjamin Banneker Elementary thesis report … · Michelle Baldwin – Mechanical Option 8 Benjamin Banneker Elementary CO 2 sensors are required to control the ventilation requirements