Technology in Architecture
Lecture 11
Mechanical System Space Requirements
Mechanical System Exchange Loops
HVAC Systems
Mechanical Room Sizing
Mechanical Room
Contains primary equipment (boiler,
chiller, etc.)
Usually adjacent to other service areas
(loading docks, electrical substation,
transformer vault, etc.)
Generally away from public
entry
Include space for
service/maintenance
S: p. 406, F.10.18
Mechanical
Room Sizing
Generally sized
based on total
floor area in
building served
S: p.399, T.10.3
Mechanical
Room Sizing
Size mechanical
room space
Application
Square Footage
S: p.399, T.10.3
Mechanical
Room Sizing
Sizing Example
150,000 SF
Department Store
Mechanical Room: 3,200 sf
S: p. 399, T.10.3
Fan Room Sizing
Fan Rooms
Contain secondary
equipment (air handlers,
heat exchanger, etc.)
Usually adjacent to or
within area served
Include space for
service/maintenance
S: p. 426, F.10.42
Fan Rooms
Require connection/
access to fresh air
Require means of
discharging return air/
exhaust air
Minimum 25’ distance of
fresh air inlet away from
contaminant source
University of Michigan Hospital,
Ann Arbor, MI
Fan Room
Sizing
Generally sized
based on total
floor area of the
thermal zone in
building served
S: p. 400, T.10.4
Fan Room
Sizing
Size fan room
Application
Square Footage
S: p. 400, T.10.4
Fan Room
Sizing
Sizing Example
150,000 SF
Department Store
Supply/Return Mains: 120 sf
for each
Fan Room: 5,200 sf
Fresh Air Inlet: 500 sf
Exhaust Air Outlet: 400 sf
S: p. 400, T.10.4
Fresh Air Inlets
Avoid contamination sources (25’ minimum)
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Loading docks
Smoking areas
Cooling Towers
Exhaust air outlets
Plumbing vents
Others…
Mechanical System
Exchange Loops
Mechanical System Exchange Loops
Heat is removed/
added via heat
exchange loops.
S: p. 402, F.10.15
Mechanical System Exchange Loops
Cooling Mode
S: p. 402, F.10.15
Mechanical System Exchange Loops
Heating Mode
S: p. 402, F.10.15
Cooling Tower
Cooling Tower
Divided into a series of
cells for redundancy/
serviceability
Significant structural load:
Rooftop vs At-grade
Potential air
contamination
Locate based on
prevailing wind direction
S: p.415, F. 10.30
Cooling Tower
Service access needed for
water treatment/debris
removal
Biocides can cause etching
on glass and other
surfaces
Minimum 25’ distance
away fresh air inlet or
fenestration
University of Michigan Hospital,
Ann Arbor, MI
Cooling Tower
Sizing
Sizing Example
150,000 SF
Department Store
Cooling Tower: 560 sf
S: p.399, T.10.3
HVAC Systems
System Types
All-Air
Air-Water
All-Water
Unitary Refrigerant System
Selection Criteria
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Control capability and
flexibility required
Environmental requirements
Cost of construction
Energy consumption
System effficiency
All-Air Systems
Heating/cooling media delivered via air only
Advantages:
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Humidification & Heat recovery
Complex zoning
Close humidity & temperature control (exc. VAV)
Can use outside air for economizer cycle
Disadvantages:
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Special care for maintenance access
Supplemental perimeter radiation may be needed
Higher volume of space needed
All-Air Systems
Single zone
Terminal reheat
Multizone
Dual duct
Variable air volume (VAV)
Single Zone
One thermostat controls
several rooms in a single
thermal zone
Applications requiring air
filtration and humidity
control
Uneven comfort for
multiple rooms
Terminal Reheat
One thermostat
controls one room as
a single thermal zone
with a reheat coil
control discharge air
temperature
Poor energy efficiency
Multizone
One thermostat controls
discharge dampers to
adjust air temperature
to each room
Small buildings with
limited distances for
duct runs
Simultaneous heating
and cooling
Dual Duct
One thermostat controls
mixing box for each room
Applications requiring
precise control of
temperature and
humidity
Energy inefficient
High maintenance
Expensive to build
Variable Air Volume
One thermostat controls
VAV valve for each room
and reduces airflow under
lower load
Applications where loads
vary significantly (offices,
schools)
Poor humidity control
Subcooling
Distribution Paths
Air may be distributed from the ceiling or the floor
Distribution Paths—Ceiling
Conventional distribution
is from the ceiling
Air discharge: 55ºF
Velocity is 100-500 fpm
S: p.439 F.10.54
Distribution Paths—Floor
Also known as
displacement cooling
Air discharge: 60+ºF
Velocity is slower than
ceiling discharge
Higher ceilings
S: p. 433, F.10.48
S: p. 394, F.10.12
Air-Water Systems
Heating/cooling media delivered via air and water
Advantages:
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Flexible placement
Centralized humidity and filtration
Space heating
Disadvantages:
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Condensation
Noise
Induction
Fan Coil Unit
S: p. 396, F.10.13
All-Water Systems
Heating/cooling media delivered via water only
Advantages:
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Flexible placement
Space heating
Disadvantages:
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Condensation
Noise
Fan Coil Unit
Fan draws air from room across coils
Flexible
Less space
Low cost
Noise
Poor ventilation/humidity
Maintenance
Condensation control
Simultaneous heating and cooling
S: p. 398, F.10.14
Unitary Refrigerant System
Heating/cooling media delivered via local equipment
Advantages:
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Individual room control
Independent heating and cooling
Single zone affected by malfunction
Low initial cost
Reliability
Disadvantages:
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Short life
Noise
Humidity control
Air filtration
Ventilation
Through the wall air-conditioning
Heat pumps