1. and weekends, winter/spring/summer breaks, and holidays, but also for
during-day better control of the temperatures of the classrooms. In Powers
Annex, Chilled Water Air Handler Unit is used and controlled by analog
controller set to 73°F. 30% of air is conditioned outside air which is an
important aspect of the classroom – air quality for students. Simple physics is
used to calculate the amount of energy used for cooling. Someone said “a
Heating, Ventilating, and Air Conditioning system is like a faucet and your
building envelope like a cup. The leakier your cup is, the more you have to open
up the faucet1.” For example, a room may be hot in the morning and cooler in
the afternoon because the temperature outside of the building is in constant
movement, and therefore more or less cooling is needed based on the outside
temperature. Other factors impacting heat gain are location of the room;
equipment in the room; the number of students in the room and their activity
level. To be precise, heat flow depends linearly on the difference of
temperatures of the inside and outside, ΔT, insulation of the building, U-value,
and square footage of the surface area of the perimeter envelope, A, i.e.,
in BTU/h. A more modern formula for
heat gain is
given in BTU, where CDD stands for
Cooling Degree Days. CDD is the number
of degrees a day’s temperature is higher
than a set room temperature.
Barry University, Miami Shores, Florida 33161
Efficiency of Air Conditioning at Barry University
Riann Zabaleta, Cassandra Denning, Vania Arboleda, Brittni Bent, Suheyl Cloak, Wesam Azaizeh,
Megan Henneberry, Thalia Altamirano , Michael Wise, Maurizio Giannotti, Sanja Zivanovic
Department of Biology & College of Health
Sciences
Barry University
11300 NE 2nd Ave.
Miami Shores, FL 33161
Phone: (305) 899-3212
szivanovic@barry.edu
After years of complaints from professors, staff, and students that certain
rooms and/or buildings at Barry University are very cold, we decided to
look into efficiency of air conditioning (A/C) that is in use. There are
several items that can be looked into when it comes to improving A/C
efficiency such as temperature of the room, humidity, air quality, A/C unit
itself, and level of CO2 in the room. For the purpose of this project we will
focus on evaluating room temperature and humidity based on the
outside climate conditions. In particular, we will collect temperature and
humidity measurements of several classrooms. We use the Arduino
platform to develop an economical temperature and humidity
logger. Arduino is an open-source microcontroller unit that utilizes an 8-
bit AVR chip and other hardware which allow it to be easily
programmable and interfaceable . We interface an Arduino Uno R3 with a
data logging shield for SD data storage and real time clock capabilities,
and an HTU21D-F high precision temperature and humidity sensor. The
Arduino is programmed to awaken from sleep at set intervals of time to
write the sensor values to the SD card. Once data is collected, we will
compare it with recommended room temperature and humidity,
calculate possible energy savings, and essentially obtain cost savings.
An Arduino Uno R3 microcontroller is used as the platform for the sensors and
SD memory card. The HTU21D-Fby Adafruit is used as a dual sensor. It is able
to detect humidity with an accuracy of ±2% and temperature with an accuracy
of ± 1%. For data logging, the Adafruit Data Logging Shield** was used. For
convenience, it houses a built-in Real Time Clock (RTC) with a dedicated coin
cell battery for persistent time keeping. The shield does not come with soldered
headers to plug in to the Arduino pins, so stacking headers were purchased and
soldered onto the shield. Likewise, plain headers were soldered onto HTU21D-F
sensor, which in turn was soldered onto the prototyping area in the center of
the data logging shield.
Both components communicate with the Arduino using I2C protocol, a
communication standard that uses only two pins and can handle interfacing
many complex boards together. The SCL pin is the clock (timing) signal, an the
SDA pin is the data signal. Connections as shown below were soldered from the
sensor pinouts to the Arduino pins. The software libraries “SD.h”, “Wire.h”,
“Adafruit_HTU21DF.h”, and “RTClib.h” were used to call sensor values and write
data. Finally, the Arduinos were powered from 6 AA batteries in series.
Figure 1. Left: Arduino Uno R3. Middle: HTU21D-F temperature and humidity
sensor. Right: Adafruit Data Logging Shield.
1. Trane. Trane Air Conditioning Manual. 53rd ed. South Florida: Trane, 1977.
2. Turner, Wayne C., and Steve Doty. Energy Management Handbook. 8th ed. N.p.: 1466578289, 2012.
3. http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/50152/If-You-Think-Thermostat-Setbacks-Don-t-Save-Energy-
You-re-Wrong.
4. "R-values of Insulation and Other Building Materials." Architect's Technical Reference. http://www.archtoolbox.com/materials-
systems/thermal-moisture-protection/rvalues.html. Archtoolbox.
5. "Wall Assembly R - Value.“ http://www.easternct.edu/sustainenergy/EnergySeminars/documents/RValueTables.pdf. Eastern
Connecticut State University.
Many buildings in Florida are perhaps much cooler than necessary, the
reason being not just high temperature outside, but the combination of
high temperature and high humidity. “To most people 75°F and 60% RH
feels like 79°F and 30% RH1.” Turning the A/C on is the easiest way to get
rid of moisture in the air, but what is the aftermath of that? In recent
years we have been hearing a lot about global warming due to human
impact; scientists have predicted the rise of the ocean, with a great
impact on Florida’s coast; many organizations are promoting
Earth/energy saving. “Florida’s per capita residential electricity demand
is among the highest in the country, due in part to high air-conditioning
use during hot summer months” (FESC). The situation at Barry
University is not different. Most classrooms are freezing. We watch
students wearing sweaters inside while outside is 90°F and at the same
time we fear the rise of the ocean? It is clear that over-cooling means
wasting energy, so should we sit and watch or should we do something
about it?
In this project, we investigate A/C efficiency of Powers Annex building;
we calculate possible energy savings per year and turn this into cost.
Finally, based on our results, we give an estimate of the possible energy
and cost saving of the whole university.
Many factors impact efficiency of A/C such as temperature, humidity, air
quality, A/C unit itself, insulation of the building, etc. For the purpose of
this project we are looking into energy savings if analog controllers were
replaced by digital ones and controlled remotely. This does not just allow
for temperatures setbacks when classrooms are not in use, such as nights
65
70
75
80
85
90
0 20000000 40000000 60000000 80000000 100000000 120000000 140000000
Temp in F 166C Temp in F 166B
3/13/15 6:15pm - 3/15/15 1am
Ceiling R VALUE
5/8" GYPSUM BOARD 0.56
6" BALT INSULATION 19
ACOUSTICAL CEILING TILE 1.485
total R 21.045
u value 0.048
total A 442.17
UA 21.01
Window R VALUE
ALUM. SINGLE HUNG
WINDOW 2.78
1/4" GLASS 0.91
ALUMINIUM WINDOW SILL
(TYPICAL) 0.05
total R 3.74
u value 0.27
Total A 13.14
UA 3.51
Total UA 365.51
Q(weekdays) 5976124.54
Q(weekends) 1676761.13
Q(nights) 1746626.18
Q(breaks) 1342160.81
total Q without body
heat 10741672.65
Body Heat 4074000
total Q with body heat 14815672.65
Kilowatts 4296.55
Cost (one room) $386.69
Total Cost (Powers
Annex) $1,546.76
Wall R VALUE
8" CONTRETE MASONRY
UNIT 1.11
CEMENT PLASTER 0.2
5/8" GYPSUM BOARD 0.56
total R 1.87
u value 0.53
total A 634.48
UA 339.29
Door R VALUE
insulated metal door 15
total R 15
u value 0.067
Total A 25.40
UA 1.70