1. Technology in Architecture
Lecture 11
Mechanical System Space Requirements
Mechanical System Exchange Loops
HVAC Systems

2. Mechanical Room Sizing

3. 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
M: p. 444, F.12.12

4. Mechanical Room Sizing
Generally sized based on total floor area in building served
M: p.435, F.12.7

5. Mechanical Room Sizing
Size mechanical room space
Application
Square Footage
M: p.435, F.12.7

6. Mechanical Room Sizing
Sizing Example
150,000 SF Department Store
Mechanical Room: 3,200 sf
M: p. 435, F.12.7

7. Fan Room Sizing

8. Fan Rooms
Contain secondary equipment (air handlers, heat exchanger, etc.)
Usually adjacent to or within area served
Include space for service/maintenance
M: p. 479, F.12.49

9. University of Michigan Hospital,
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

10. Fan Room Sizing
Generally sized based on total floor area of the thermal zone in building served
M: p. 436, F.12.8

11. Fan Room Sizing Size fan room Application Square Footage
M: p. 436, F.12.8

12. 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
M: p. 436, F.12.8

13. Fresh Air Inlets Avoid contamination sources (25’ minimum)
Loading docks
Smoking areas
Cooling Towers
Exhaust air outlets
Plumbing vents
Others…

14. Mechanical System Exchange Loops

15. Mechanical System Exchange Loops
Heat is removed/ added via heat exchange loops.
M: p. 439, F.12.9

16. Mechanical System Exchange Loops
Cooling Mode
M: p. 439, F.12.9

17. Mechanical System Exchange Loops
Heating Mode
M: p. 439, F.12.9

18. Cooling Tower

19. 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
M: p.465, F

20. University of Michigan Hospital,
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

21. Cooling Tower Sizing Sizing Example 150,000 SF Department Store
Cooling Tower: 560 sf
M: p.435, F.12.7

22. HVAC Systems

23. System Types
All-Air
Air-Water
All-Water
Unitary Refrigerant System

24. Selection Criteria Control capability and flexibility required
Environmental requirements
Cost of construction
Energy consumption
System effficiency

25. All-Air Systems Heating/cooling media delivered via air only
Advantages:
Humidification & Heat recovery
Complex zoning
Close humidity & temperature control (exc. VAV)
Can use outside air for economizer cycle
Disadvantages:
Special care for maintenance access
Supplemental perimeter radiation may be needed
Higher volume of space needed

26. All-Air Systems Single zone Terminal reheat Multizone Dual duct
Variable air volume (VAV)

27. Single Zone
One thermostat controls several rooms in a single thermal zone
Applications requiring air filtration and humidity control
Uneven comfort for multiple rooms

28. Terminal Reheat
One thermostat controls one room as a single thermal zone with a reheat coil control discharge air temperature
Poor energy efficiency

29. 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

30. 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

31. 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

32. Chilled Beams
Source: article.php?L=5&C=463&P=4

33. Chilled Beams
Source: article.php?L=5&C=463&P=4

34. Chilled Beams
Integration of geothermal and VAV

35. Distribution Paths
Air may be distributed from the ceiling or the floor

36. Distribution Paths—Ceiling
Conventional distribution is from the ceiling
Air discharge: 55ºF
Velocity is fpm
M: p.544 F

37. Distribution Paths—Floor
Also known as displacement cooling
Air discharge: 60+ºF
Velocity is slower than ceiling discharge
Higher ceilings
M: p. 559, F
M: p. 394, F.10.12

38. Air-Water Systems Heating/cooling media delivered via air and water
Advantages:
Flexible placement
Centralized humidity and filtration
Space heating
Disadvantages:
Condensation
Noise
Induction
Fan Coil Unit
M: p. 396, F.10.13

39. All-Water Systems Heating/cooling media delivered via water only
Advantages:
Flexible placement
Space heating
Disadvantages:
Condensation
Noise

40. 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
M: p. 398, F.10.14

41. Unitary Refrigerant System
Heating/cooling media delivered via local equipment
Advantages:
Individual room control
Independent heating and cooling
Single zone affected by malfunction
Low initial cost
Reliability
Disadvantages:
Short life
Noise
Humidity control
Air filtration
Ventilation
Through the wall air-conditioning
Heat pumps

42. ARCH-4372/6372 HVAC Distribution & Sizing HVAC Distribution Systems
Diffuser Selection and Layout
Ductwork Sizing

43. HVAC Distribution Systems

44. Distribution System Plans Symbols
Positive Pressure (supply)
Negative Pressure (return or exhaust)

45. Distribution System Plans Symbols
Arrow indicates
air flow direction

46. Distribution System Plans Symbols
Flow patterns
1-way
2-way
3-way
4-way

47. Distribution System Plans Symbols
Thermostat
Smoke/Fire
Damper T

48. Distribution System Plans Symbols
Double Line
Single Line

49. Distribution System Plans Symbols
Section z z
16 x 12 z z
12 x 16

50. Distribution System Plans
Double Line
Single Line

51. Distribution System Plans
Double Line
Single Line

52. Ceiling Plenum Plans
Shows duct path from distribution network to supply diffuser or return register

53. Diffuser Selection and Layout

54. Diffuser Selection Diffuser Selection Criteria Air flow Throw
Noise Criteria (NC) Level
Appearance

55. Diffuser Selection
Air Flow
Throw
NC Level

56. Diffuser Selection Throw: Avoid Gaps and overlap
Distance of air movement
Avoid
Gaps and overlap
Obstructions/deflectors
Velocity (fpm)

57. Diffuser Layout
1. Use Room Sensible Load (no latent, no ventilation) to determine air flow
Qs=1.08 x CFM x ΔT
where
ΔT=|Tsa-Tra|
thus
CFM= Qs
(1.08 x ΔT)

58. Diffuser Layout 2. Define Supply Air temperatures Heating:
Tsa range is ºF
Tra=68ºF
Cooling:
Tsa range is 45-55ºF
Tra=78ºF

59. Diffuser Layout 3. Define ΔT Heating: ΔT=|110-68|=42ºF Cooling:

60. Diffuser Layout 4. Determine Air Flow (CFM) CFMhtg= Qs (1.08 x ΔThtg)
CFMclg= Qs
(1.08 x ΔTclg)
Larger result determines air flow

61. Diffuser Layout
5. Revise discharge air temperature to match required air flow
CFMpeak= Qs
(1.08 x |Tsa-Tra|)
solve for Tsa

62. Diffuser Layout 6. Select diffuser layout Regular pattern
Uniform coverage
Avoid “short circuiting” with exhaust/return registers

63. Diffuser Layout Example
Office space with overhead heating and cooling supply
NC level 35
16’ 8’

64. Diffuser Layout Example
Heating Qs= 11,800 Btuh
Discharge=110ºF
Set point = 68ºF ΔT = 42ºF
CFMhtg= Qs
(1.08 x ΔT)
=11,800/(1.08 x 42)=260 CFM

65. Diffuser Layout Example
Cooling Qs=8,600 Btuh; ΔT= 42ºF
CFMclg= Qs
(1.08 x ΔT)
=8,600/(1.08 x 23)=346
CFMHTG= 260 < CFMclg =346

66. Diffuser Layout Example
Revise Heating Tsa
CFMpeak= Qs
(1.08 x ΔT)
=346=11,800/(1.08 x |Tsa-68|)
Tsa=99.6ºF

67. Diffuser Layout Example
Define Pattern
346 Cfm
Round up to 0 or 5 cfm
cfm
cfm
cfm
cfm

68. Diffuser Layout Example
Define Pattern
346 Cfm
Round up to 0 or 5 cfm
cfm 2-way
cfm 4-way
cfm 3-way
cfm 2-way
16’ 8’

69. Diffuser Selection
NC 35
Air Flow
Throw
Select 8” Rd 4-way

70. Diffuser Layout Example
Define Pattern
346 Cfm
cfm 4-way 4’ 4’ 4’ 4’
16’ 4’ 4’ 4’ 4’ 8’

71. Return Register Selection
Selection Criteria
Air flow
Noise Criteria (NC) Level
Appearance

72. Return Register Selection
Air Flow
NC Level

73. Return Register Layout
Avoid
Short circuiting with supply diffusers
Locating in visually obtrusive location

74. Return Register Layout
Define Pattern
Supply=350 cfm
Return
cfm
16’ 8’

75. Return Register Selection
Air Flow 350 cfm
NC Level 35
Select 10” x 8” 350 cfm NC 27db

76. Return Register Layout8’
16’
Define Pattern
Supply=350 cfm
Return
cfm
10” x 8”
NC 27db