222 N. Columbus Drive – Mechanical Ventilation Systems Review
222 North Columbus Drive
Mechanical Ventilation Systems Review
4/15/08
222 N. Columbus Drive – Mechanical Ventilation Systems Review
I.
EXECUTIVE SUMMARY ................................................................................................................................... 2
II.
BUILDING DESCRIPTION ................................................................................................................................ 4
III.
MECHANICAL VENTILATION SYSTEM DESCRIPTIONS........................................................................ 5
A.
MAKEUP AIR UNITS (S-1 & AHU-2/AHU-3) ....................................................................................................... 5
B.
TOILET EXHAUST FANS (TEF-1, TEF-2, TEF-4, & TEF-5) .................................................................................. 7
C.
DRYER EXHAUST FAN (DEF-1).............................................................................................................................
7
IV.
VENTILATION SYSTEM TEST RESULTS .......................................................................................................
V.
CORRECTIVE MEASURES .................................................................................................................................
CM#1 -
MODIFICATION TO EXISTING MAKEUP AIR INTAKE ......................................................................................
CM#2 -
REDUCTION OF ITEMS AGGRAVATING STACK EFFECT ..................................................................................
CM#3 -
INSTALL DEMAND RESPONSE VENTILATION .................................................................................................
Page - 1
222 N. Columbus Drive – Mechanical Ventilation Systems Review
I. EXECUTIVE SUMMARY
Ventilation systems have a critical role in the performance of high rise residential buildings, not just
with respect to energy, but also from a comfort and quality perspective. Building management at
222 N. Columbus Drive has enlisted Elara to perform an objective audit of the building’s ventilation
systems. The critical goal of this report is to identify and recommend a solution to: 1.) The noise
complaints around the buildings elevator shafts at the first floor believed to be associated with the
building’s ventilation system and 2.) The primary makeup air units (S-1) filter clogging issues
believed to be caused by a combination of effective area of the intake louver and associated damper
as well as uncontrollable winds carrying precipitation. Additional focuses of the report include
enhanced controls of building pressurization and energy efficiency. The following is the scope of
work contained in this report:
• A review of the existing architectural, mechanical, structural and electrical drawings in order
to identify the original design intent of the systems
• An onsite review of the building’s ventilation systems, namely the building’s makeup air
units, exhaust fans and building envelope in order to identify the existing conditions
• Conduct interviews with building maintenance staff to determine where the complaints are
centralized
• Testing of the mechanical ventilation equipment to identify what the actual operating
conditions are and to assess the amount of infiltration caused by pressure imbalances
• A list of Corrective Measures (CMs) which address the critical issues described above
Corrective Measure Summary
Based on the results of our onsite observations, interviews with maintenance staff, review of the
drawings and equipment test data, this report has identified three corrective measures that are
recommended to be implemented; 1) Modifications to Existing Makeup Air Unit Intake, 2)
Reduction of Items Aggravating the Stack Effect and 3) Install Demand Response Ventilation. The
following is a brief description of each Corrective Measure:
1)
Modifications to Existing Makeup Air Unit Intake
The assessment of the mechanical ventilation systems revealed that the effective area of
the original louvered opening is insufficient to prevent precipitation from entering the
buildings primary make up air unit S-1. As a result the air entering the louvered opening
is at a high enough velocity to carry precipitation from the opening of the louver to the
filters, resulting in clogging issues. There are two possible corrective measures that have
been theorized. The first method includes installing a snow/rain stopping mesh which
would remove rain/snow from incoming air before passing through the filters. The
second alternative is to increase the cross-sectional area of the intake louver, as a result
incoming air velocities would be reduced and thus entering precipitation would also
theoretically be reduced. However, this corrective measure is limited in its effectiveness
due to the prevailing wind driven precipitation towards this southern facing louver and is
therefore not recommended.
2)
Reduction of Items Aggravating the Stack Effect
The buildings natural stack effect is the primary cause of the noise complaints around
the buildings elevator shafts at the first floor. Through our investigations it was noticed
that the Air Handling Units (AHU-2, AHU-3) located on the second floor were designed
to positively pressurize the 1st floor. The excess air used for pressurization tends to exit
the first floor via the elevator shafts due to the buildings natural stack effect.
Page - 2
222 N. Columbus Drive – Mechanical Ventilation Systems Review
3)
Additionally, some of the elevator shafts continue down to the garage levels. For
example we observed that when the freight elevator is on garage level G5 (which is the
loading dock) the elevator shaft is in direct communication with the garage space and
thus allowing air to enter the freight elevator shaft again due to the buildings natural
stack effect. Finally, it was observed that a side entrance/exit door located at the first
floor on the buildings north face is used frequently, and that the freight elevator shaft is
again in direct communication with this entrance and again allowing air to enter the
elevator shaft due to the buildings natural stack effect. All of the above conditions
become the source of air that increases the buildings natural stack effect and cause the
noise complaints at the first floor elevator shafts. In addition, openings at the top of the
building where natural stack effect air was exiting the building were also identified as
aggravating the buildings natural stack effect. Corrective measures listed in order of
importance to reduce the buildings natural stack effect are as follows: , 1.) Install
secondary door in corridor 114 just inside north side entrance/exit door to minimize air
infiltration to elevator shaft, 2.) Rebalance AHU-2 and AHU-3 to specified return and
exhaust quantities, 3.) Install motors on loading dock doors leading to freight elevator to
minimize the amount of time the doors are open. 4.) Install motorized dampers on garage
outside air intakes and interlock with garage exhaust fans to minimize the amount of air
entering the building 5.) Install motorized damper on GEF-10 opening to roof. 6.) Install
motorized damper on emergency refrigerant exhaust fan and operate fan only on
refrigerant leak detection and excess chiller room temperature. 7.) Seal openings into
penthouse mechanical/electrical switch room from lower floor. These corrective
measures would decrease the buildings natural stack effect and reduce the noise
complaints around the buildings elevator shafts at the first floor.
Install Demand Response Ventilation
The assessment of the mechanical ventilation systems has shown that the building’s
kitchen and toilet exhaust are constant volume. The current City of Chicago Building
Code allows buildings to control the exhaust in these spaces using occupancy. If an
occupancy based exhaust system is installed, it is estimated that the amount of air
exhausted would reduce by an average of 50%. In doing so the amount of infiltration
caused imbalances would also be reduced. If this recommendation is combined with the
reduction of items aggravating the stack effect, the infiltration would be greatly reduced
during the majority of operating hours.
Further information regarding the impact of these recommendations can be found in the subsequent
sections of this report.
Page - 3
222 N. Columbus Drive – Mechanical Ventilation Systems Review
II. BUILDING DESCRIPTION
The condominium building located at 222 N. Columbus
Drive in downtown Chicago was built in 2002. The total
residential portion of the building is 516,000 ft2 and has
a total of 466 condominium units. The building is 52
stories high and has 6 levels of garage space totaling
650,000 ft2 in total gross area. The exterior envelope of
the building is comprised of primarily concrete, brick
and glass.
The buildings main mechanical ventilation system is
comprised of one kitchen exhaust fan, four toilet exhaust
fans, two dryer exhaust fans, and one makeup air unit
(S-1). All of these systems are original to the building
and have had few repairs and modifications throughout
their short operating life. A detailed description of all
the mechanical ventilation equipment, including their
original design and current condition, can be found in
the following section of this report.
A breakdown of each level beginning with the basement is as follows:
• The below grade level garage is predominately intended for tenant parking; however it also
houses a Com-ED room.
• The 1st floor ground level includes the lobby, tenant mail room, as well as management
offices and elevator lobbies.
• The 2nd floor level includes a sauna, fitness center, lounge, and an indoor pool.
• Floors 3 through 46 are comprised of condominium units; floor plan variations are small,
although a typical layout differs between 10 to 12 condominium units depending on the
floor.
• The 47th through 52nd floors differ in that they convert to the penthouse layout in which three
3 bedroom units are allocated per floor.
• The 53rd floor is the mechanical penthouse, which houses the ventilation systems and
elevator machine room.
Page - 4
222 N. Columbus Drive – Mechanical Ventilation Systems Review
III. MECHANICAL VENTILATION SYSTEM DESCRIPTIONS
A. MAKEUP AIR UNITS (S-1 & AHU-2/AHU-3)
The makeup air unit (S-1) was originally designed to supply 70,000 cubic feet per minute (CFM) of
conditioned outside air to the corridors on levels 2 thru 52 and is located on the 53rd floor in the
mechanical penthouse. The makeup air is distributed in the corridors at one common location on
each floor. Each typical floor was designed to be supplied with 1,200 CFM of conditioned outside
air. Each individual corridor supply can be regulated individually using manual balancing dampers.
The operation of the MAUs is as follows:
• Air enters through a louver and
associated outdoor air damper.
• The air then passes through a bank
filters
• The air then passes across the coil
sections.
• Air, first passes through the heating
coil. The heating coil uses hot water to
heat the air passing through it, during
heating mode.
• After the heating coil, the air passes
over the cooling coil section. The
cooling coil is a chilled water type coil
and provides cooling from a centralized
chiller plant, during cooling mode.
• The air, once conditioned, is then supplied to the corridors using a 100 hp centrifugal fan.
The fan is constant volume and belt driven. The fan operates at single speed and has no
controllable means to vary the volume of air supplied.
Two additional air handling units AHU-2 & AHU-3 serve the first floor, each of which are designed
to supply 6,000 cubic feet per minute of conditioned outdoor air to the two different sections (north
and south) of the buildings first floor. AHU-2 serves the office spaces south of the buildings
elevator lobby and has a dedicated exhaust fan. AHU-3 serves the main lobby and common areas
north of the buildings elevator lobby and is designed to return a portion of the air quantity, however
the return is not sufficiently sized thus these spaces are being pressurized by design. The operation
of the AHU’s is as follows:
• Air enters through a louver and associated outdoor air damper.
• The air then passes through a bank filters
• The air then passes across the coil section.
• Air, first passes through the heating coil. The heating coil uses hot water to heat the air
passing through it, during heating mode.
• After the heating coil, the air passes over the cooling coil section. The cooling coil is a
chilled water type coil and provides cooling from a centralized chiller plant, during cooling
mode.
• The fans on both units are run at a constant speed; however AHU-2 was retrofitted with inlet
vanes, allowing the air quantity supplied to be varied. The inlet vanes on AHU-2 are
Page - 5
222 N. Columbus Drive – Mechanical Ventilation Systems Review
modulated according to pressure readings taken in the ductwork between the unit and the
variable air volume (VAV) boxes that serve the individual office spaces.
S-1 Operational Observations:
1. The main MAU (S-1) outdoor air dampers are
typically kept 100% open.
2. The effective area of the combination of the
intake louver and its associated damper are
undersized for the design air quantity.
3. It was observed that the intake plenum was
under a positive pressure at times, which is very
unusual; normally this plenum should be under
negative pressure. This was observed as being
caused by the wind.
4. The MAU’s fan does not have a two speed
motor or variable control of the volume of air
supplied, thus the makeup air for the building is
constant volume.
AHU-2 Operational Observations:
1. AHU-2’s outdoor air, parallel, dampers were
75% open and the dampers allowing the air to be
sent to the exhaust fan were approximately 80% open.
2. The AHU does not have a variable speed controlled motor, however as mentioned before the
units centrifugal fan was retrofitted with inlet vanes.
3. The outdoor dampers are manually set to be proportionally open; however they are
controlled such that they will shut before the chilled water coil freezes. They appear to be
functioning properly.
4. Also it should be noted that exhaust/return duct is fed by a “plenum” type ceiling, which is
considered an ineffective design to collect and return air directly from the spaces served.
AHU-2 is positively pressurizing the south zone which it is serving.
AHU-3 Operational Observations:
1. AHU-3 outdoor dampers were 75% open.
2. The centrifugal fan located on this unit was not retrofitted with inlet vanes, therefore it is
constant volume.
3. It should also be noted that the return on this unit is ducted, however has only two locations
on the north zone from which it can collect return air.
Page - 6
222 N. Columbus Drive – Mechanical Ventilation Systems Review
B. TOILET EXHAUST FANS (TEF-1, 2, 4, & 5)
•
The toilet exhaust fans were originally designed to exhaust 49,390 CFM from the bathrooms
of the building they are split into high and low zones and are located on the roof and level
G1 of the garage. There are four main toilet exhaust branches serving the condominium
units. Each typical floor was designed to have approximately 950 CFM of toilet exhaust
ranging from 65 CFM to 120 CFM from each bathroom.
TEF-1 & 2 Operational Observations:
1. These toilet exhaust fans do not have
any means to vary the exhaust volume
of air and the fan is single speed.
Therefore, the toilet exhaust is constant
volume.
TEF-4 & 5 Operational Observations:
From submittal specifications these toilet
exhaust fans were fitted with a motorized
volume damper; however it does not
appear that they are automatically
controlled. Verification is recommended
to ensure that the dampers are operational.
C. DRYER EXHAUST FAN (DEF-1)
The main dryer exhaust fan was originally
designed to exhaust 15,840 CFM from the
dryers and is located on garage level G1.
Each typical floor was designed to have
approximately 380 CFM of dryer exhaust.
The buildings main dryer exhaust fan is
constant volume utilizing a 10 hp centrifugal
fan.
Page - 7
222 N. Columbus Drive – Mechanical Ventilation Systems Review
IV. VENTILATION SYSTEM TEST RESULTS
In this section the buildings ventilation test results will be presented. The noise found in and around
the elevator shaft at the first floor is due to pressure imbalances throughout the building, moreover a
well defined phenomenon called the stack effect is occurring. It is also the intention of this section
to further describe the stack effect and other factors influencing high rise building pressure
imbalances, how they occur and how they can be corrected.
The three major principles driving pressure differences across the buildings exterior are: stack
effects (thermal buoyancy), wind effects, and unbalanced mechanical ventilation systems. The stack
effect in a building is the result of warm air rising up through vertical shafts and passage ways in the
building. The stack effect is a function of the temperature difference between the outside and inside
air, the height of the building and the internal resistance to vertical air flow. The stack effect is
greatest when it is cold outside because the temperature difference between the outside and inside
air is greatest. During the summer months, the stack effect is usually negligible because of the small
temperature difference between the outside and inside air.
Flow Out Of Bldg
Inside Bldg
Neutral Pressure
Level
Air
Out
Air
Out
Neutral Level
Air
In
Flow In Bldg
Air
In
Pressure
Ground
St a ck A c t ion Onl y
TYPICAL BUILDING WITH NO WIND
The above diagrams illustrate how there is variable pressure differences across the building’s
envelop. Towards the bottom of the building, the building pressure is negative with respect to the
outside pressure and towards the top of the building, the building pressure is positive with respect to
the outside pressure. Somewhere between the bottom and top of the building, the building pressure
is equal, or neutral, to the outside pressure. Therefore, the infiltration of air into the building due to
the stack effect is greatest at the bottom of the building.
To minimize infiltration caused by the stack effect, steps should be taken to minimize the
unrestricted flow of air vertically through the building. Particular attention should be given to
stairways and elevator shafts. Stairway and elevator doors should have tight seals. Openings at the
top of these shafts should be minimized.
The second major principle driving pressure differences across a high rise building is wind. Wind
tends to enter the windward side of the building due to the kinetic energy of the wind being
converted into positive pressure on the building exterior. On the leeward side of the building, the
opposite occurs. Wind tends to create a negative pressure on the building exterior enhancing
exfiltration of air from the building.
Page - 8
222 N. Columbus Drive – Mechanical Ventilation Systems Review
The third major influence on building pressures is the building’s mechanical ventilation systems. If
the mechanical systems are balanced, i.e. the supply of outside air equals the exhaust, then the
building’s pressures are unaffected. However, if the supply of outside air is less than the exhaust,
the neutral pressure level shown in the earlier diagram will go up in the building. If the supply of
outside air is greater than the exhaust, the neutral pressure level will go down decreasing this stack
effect and the infiltration of outside air. Some of the symptoms of a building that is out of balance
include whistling noises around the lower elevator doors, problems with the elevator doors closing,
whistling noises around exterior window seals, complaints of odors, water infiltration problems, and
inadequate exhaust in parts of the building.
Of these items two can be feasibly controlled and corrected in this particular building, namely the
items contributing to the stack effect and imbalances of the buildings mechanical ventilation
systems.
The major contributors to the stack effect at the bottom of this building are the unrestricted outdoor
air supply to the garage levels, unrestricted connection between the buildings garage and freight
elevator shaft, unrestricted connection between the buildings north entrance/exit door and freight
elevator shaft, the pressurizing of the lower levels of the building by AHU-2 and AHU-3 and the
poorly sealed elevator shaft lobby doors. The major contributors to the stack effect at the top of this
building are the openings to the penthouse from the floor below and some openings in the
penthouse to the exterior.
The second controllable item influencing pressurization is derived from the building’s mechanical
ventilation systems. Specific components of the facility’s mechanical ventilation system focus on
adding and removing air from the building. The major points of exhaust are from toilet, drier, and
kitchen exhaust fans, while replacement air is distributed via makeup air units (mainly S-1, other
contributions from AHU-2 & AHU-3). Based on the original design and according to the building
drawings, Park Millennium exhausts 87,670 CFM and is replaced with 70,000 CFM of conditioned
outside air. As the toilet, dryer, and kitchen exhaust fans have no volume control, they are constant
volume. So based on the original design, the makeup air unit was designed to replace 80% of the
air exhausted with conditioned outside air. With the mechanical ventilation system designed to
makeup only 80% of the air exhausted, the balance of outside air would enter the building wherever
the path of least resistance lies. This may be through the garage, through the windows in the units,
or through other entrances into the building. In any case, this unconditioned and unfiltered outside
air is eventually conditioned by the building systems.
It should be noted that in practice it is rarely the case that mechanical ventilation systems perform
exactly as designed. As a result, the design exhaust values are likely not the actual exhausted
volumes. Therefore, an analysis of the ventilation in the building could not be performed properly
without measuring actual air flows of the equipment. As such, Elara enlisted the help of a local
contractor to measure the air flows of the building’s main ventilation equipment (4-toilet exhaust
fans, 1-kitchen exhaust fans and makeup air unit S-1). The results of the measurements are shown
in the table below:
Page - 9
222 N. Columbus Drive – Mechanical Ventilation Systems Review
System
Design
Air
Flow
(CFM)
Park Millennium
Dryer Exhaust Fan-1 (DEF-1)
15,840
Toilet Exhaust Fan-1 (TEF-1)
10,195
Toilet Exhaust Fan-2 (TEF-2)
13,345
Toilet Exhaust Fan-4 (TEF-4)
11,825
Toilet Exhaust Fan-5 (TEF-5)
11,825
Other Exhaust Contributors
(actual measurements not
performed)
24,640
Exhaust Total
87,670
Makeup Air Unit (S-1)
70,000
Imbalance (CFM)
-17,670
Percentage of Made Up Air (%)
80%
Actual
Percentage
Measured
of Design
Air Flow
(%)
(CFM)
12,818
9,593
10,278
11,475
14,184
24,640
82,988
67,233
-15,755
81%
81%
94%
77%
97%
120%
100%
95%
96%
-----
Test data observations:
• As the table above shows, most of the existing equipment is operating slightly below design
capacity.
• Overall the data shows that the building is slightly negatively pressurized due to mechanical
ventilation system imbalances. Based on our onsite observations, the location of the highest
infiltration into the building is through the garage.
Page - 10
222 N. Columbus Drive – Mechanical Ventilation Systems Review
V. CORRECTIVE MEASURES
The following are recommendations which address the goals of the report as described in the
executive summary.
CM#1 -
MODIFICATIONS TO EXISTING MAKEUP AIR UNIT INTAKE
This recommendation addresses one of the critical goals of this report. As described previously, the
incoming air velocity is at such a high rate that precipitation is being swept into the makeup air
units filters and as a result clogging the unit’s filters. The results of the test data concluded that
makeup air unit S-1 is currently conditioning approximately 67,000 cfm, which after a simple hand
calculation yields air velocities in upwards of 1120 ft/min. From louver specifications at a free area
face velocity of 903 ft/min water penetration begins. As can be seen under current operating
conditions the velocity is at too high a rate to prevent water penetration. Below the two corrective
measures are listed in order of priority based on the ease of installation and impact each measure
will have on the MAU’s filter clogging issues.
For this corrective measure it is recommended
that a primary precipitation filtration system be
installed in front of the existing filter bank and
thus the existing filter bank would become the
secondary filtration system. The primary
filtration bank would be intended to remove
precipitation from the incoming air and the
second would further filter the air, serving the
same purpose as it currently serves. This
primary filtration system would ideally have a
heating element in order to remove snow
particles from the air during winter months.
The following bullet points describe the
impact of the project in more detail:
• The installation of a snow stopping mesh would provide an effective guard against the
penetration of snow from outdoor air to filters.
• Allows for uninterrupted operation of the main makeup air unit during snow/rain events.
• Sufficient drainage in plenum and filter section has been installed during a previous
improvement.
• Decreased filter maintenance/replacement due to less moisture passing through them.
• Less fabrication work compared to replacement/demolition of existing louvered opening.
• Some maintenance would be needed as the snow/rain stopping mesh would have to be
cleaned twice per year.
The implementation of this recommendation requires the installation of a primary filter bank which
is constructed from a fine mesh designed to collect rain/snow from the incoming air stream.
Installing such a device would include moderate sheet metal work as a new filter bank would need
to be fabricated in front of the existing filters. It is recommended that a heating element is also
installed to facilitate melting of snow that would be collected on this filter bank in a snow event.
The heating element would necessitate automatic/manual controls as well as electrical connections.
Page - 11
222 N. Columbus Drive – Mechanical Ventilation Systems Review
It is estimated that the implementation of this recommendation would require and investment of
approximately $47,500, as well as interruptions of makeup air service while construction is taking
place.
This corrective measure is not currently recommended, however for future consideration purposes
the description is as follows, a bank of ductwork is fabricated such that it is attached to the louver
which is on the buildings north wall which is approximately 15’ past the now functional louver.
There would be a necessity to create a new opening in S-1’s existing intake plenum; the ductwork
would connect the secondary intake louver to the primary louver that is serving S-1. Effectively
increasing the cross sectional area of the primary intake louver and thus reducing incoming air
velocities.
• Reduces air velocities and thus directly reduces the amount of precipitation entering the
lover.
• Allows for uninterrupted operation of the main makeup air unit during snow/rain events.
• It is theorized that even with this work the winds coming from the southwest would still
have a tendency to swept precipitation into the intake.
• Large amount of fabrication work.
• It is hard to precisely determine how much incoming precipitation would be reduced.
The estimated implementation cost has not been analyzed due to the unknown effectiveness of this
modification.
Page - 12
222 N. Columbus Drive – Mechanical Ventilation Systems Review
REDUCTION OF ITEMS AGGRAVATING THE STACK EFFECT
From field observations we have been able to identify a number of contributors of the phenomenon
known as the stack effect. It is hard to determine if all have been identified, however we are
confident if corrective measures are taken to improve these problems that there will be a significant
reduction in the stack effect and as a result the noise issues around the buildings elevator shafts
would be reduced. The following features were
identified as the most likely contributors and are
listed in order of priority based on the impact
each has on the stack effect.
•
•
•
•
•
•
•
The absence of a secondary door to the
buildings side exit/entrance in corridor
114 on the north side of the building.
Current operation of AHU-2 and AHU-3
and their intended purpose of
pressurizing the 1st floor and the absence
of ducted returns to AHU-2.
The unrestricted flow of air from the
garage levels to the building main
elevator shaft; in particular attention
should be invested in garage level G5
where the loading docks are continuously
kept open allowing for large quantities of
air to pass thru this area.
The absence of intake dampers on all
garage levels from main intake plenum.
The damper on the roof connected to
GEF-10 is completely non-functional.
The absence of dampers on GEF-9
ductwork currently drawing exhaust from
the mechanical penthouse.
The openings in the electrical switch gear
room open to the level below.
Each of these items if addressed should
positively impact and reduce the buildings stack
effect.
As such, it is recommended that a
corrective action is taken to address each of
these issues.
•
A secondary door should be installed in
the north corridor 114 of the building to
limit the amount of air infiltrated; this
exit/entrance was not initially intended to
be used at the amount of use it is
currently receiving. Special attention
Page - 13
222 N. Columbus Drive – Mechanical Ventilation Systems Review
•
•
•
•
•
•
should be paid to the fact that the enclosure must be fitted to the floor slab above, because in
its current configuration the ceiling space is a plenum used to return air and thus would
allow air to pass through. The implementation of this recommendation is estimated to
require an investment of approximately $10,000 depending on level of finishing.
Rebalance AHU-2 and AHU-3 supply quantities to specified return and exhaust quantities.
The implementation of this recommendation is estimated to require an investment of
approximately $3,000.
The doors on garage level G5 should be fitted with motors that will open/close with
automated operation. The implementation of this recommendation is estimated to require an
investment of approximately $1,000.
Each level of the garage supply openings should be fitted with automated dampers
interlocked with the associated garage exhaust fans. The implementation of this
recommendation is estimated to require an investment of approximately $35,000.
A new damper should be installed on the opening to general exhaust fan 10 (GEF-10) from
the mechanical penthouse. The implementation of this recommendation is estimated to
require an investment of approximately $1,500.
GEF-9 ductwork in the mechanical penthouse should be outfitted with motorized dampers
controlled by refrigerant leakage sensors. The implementation of this recommendation is
estimated to require an investment of approximately $1,500.
The openings in the electrical switch room were meant to house conduit however they are
unused and should be sealed. Sealing of these opening can be done by in-house staff.
Page - 14
222 N. Columbus Drive – Mechanical Ventilation Systems Review
CM#2 -
INSTALL DEMAND RESPONSE VENTILATION
This recommendation stems from the use of the building’s bathroom and dryer exhaust system.
Currently, both the bathroom and dryer exhaust systems are constant volume. The total amount of
exhausted air must be made up by either conditioned makeup air, or infiltration. As discussed
previously, the existing system is designed to replace 80% of the air exhausted and actually replaces
81%. Approximately 80% of the exhausted air is replaced by the building’s makeup air system; the
other portion of air is infiltrated.
It is recommended to convert the existing constant volume ventilation system to a demand response
ventilation system. By exhausting air from the occupied drier
and bathrooms only, the system can take advantage of nonoccupied periods to reduce the overall energy usage in the
building while minimizing infiltration. The conversion requires
that automated extraction units be installed in each bathroom as a
replacement for the existing grills. The extraction units have an
occupancy sensor that triggers a damper to open and facilitate
exhaust. They would limit the amount of air exhausted from the
bathrooms to periods when it is necessary and required by City of
Chicago Code. The extraction units would be installed with a
mounting plate designed specifically for 222 N. Columbus Drive.
The extractor consists of a battery operated damper motor and an
infrared sensor. The damper stays open for 15 minutes after the
occupant leaves the room. Battery life is expected to be multiple
years. The use of a battery enables the units to be installed without any electrical work. The
specific impact of implementing this recommendation is described below:
• It is estimated that the conversion would result in a 50% reduction in bathroom and dryer
exhaust air flow on average. This would result in cooling, heating and fan power energy
savings as well as further reduce noise levels.
• The impact of infiltration would be minimized and even eliminated during periods of low
occupancy. However, for most of the operating hours, the building would still be under a
negative pressure. As a result, the negative effects resulting from infiltration, such as
moisture damage and infiltration through the garage would be mitigated but not eliminated.
The results of implementing this recommendation are presented below:
♦ Natural Gas Savings
62,474 therm/yr
♦ Electrical Energy Savings
277,300 kWh/yr
♦ Total Energy Cost Savings
$67,484/yr
♦ Estimated Implementation Cost
$325,000
♦ Simple Payback
4.8years
If the installation of the extraction units is performed in-house, the implementation cost would be
reduced. However, the implementation would take place over a longer time period.
Page - 15