1. INTEGRATING COST & ENGINEERING
CONSIDERATIONS
IN
DESIGNS
JAYGOPAL KOTTILIL
Senior Manager (MEP Engineering)
Doha
14th May 2014

2. What & Why HVAC ???
Heating, Ventilating, Air‐Conditioning

3. Traditional Zero‐Energy Air‐Conditioning

4. Modern Day Air‐Conditioning
 Temperature
 Relative Humidity
 Noise Level
 Indoor Air Quality
 Life Safety

5. HVAC in Real Estate Developments
5
 Reliable
 Robust
 Safe
 Economical
 Sustainable

6. Real Estate Developments ‐ Financials
 Expenditure
• Capital / First Cost
• Operating Cost
 Revenue
 Return on Investment
6

7. Real Estate Developments ‐ Capital Expenditure
 Land
 Infrastructure
 Building
 Professional fees
 Financing & Insurance
7

8. Real Estate Developments ‐ Operating Expenditure
 Utility (Electricity, Water, District Cooling, LP Gas, Telecom etc.)
 Facility Management (Maintenance, Replacements, etc.)
 Marketing
 Finance & Insurance
8

9. Real Estate Developments ‐ Revenues
9

10. Real Estate Developments ‐ Return on Investment
 Capital cost recovery per year spread over ‘n’ years
 Operating cost recovery annually
A. Total expenditure recovery per annum
B. Total revenue per annum
Minimize expenditure! Maximize revenue!
10

11. Infrastructure Capital Cost
11
25%
5%
15%
20%
25%
10%
Electricity
Street lighting
Potable water
Drainage (Sewer and Storm
water)
District cooling
Telecommunication

12. Building Capital Cost
12
27%
19%
22%
15%
17%
Structure
Envelope
Mechanical
Electrical
Interior finsihes

13. M+E Capital Cost
13
28%
5%
4%
27%
8%
6%
7%
15%
HVAC
Plumbing
Drainage
Electrical power
Voice and Data
ELV
Fire detection & protection
Sanitary appliances

14. Sustainable Developments
 Qatar National Vision 2030
• Economic Growth, Social Development and Environmental Management
• Economic development and protection of the environment ‐ neither of which
should be sacrificed for the sake of the other
 Sustainable Developments
• Urban Connectivity
• Site
• Materials
• Outdoor Environment
• Cultural & Economic Values
14

15. Electricity Usage in Qatar
0% 5% 10% 15% 20% 25% 30%
Residential buildings
Commercial buildings
Industrial use
Others
Plant use
Losses
HVAC Component
Residential buildings: 60%
Commercial buildings: 50%

16. Engineering Objectives
Optimize First Cost Reduce Energy Conserve Water

17. Sustainable design Be compassionate to the end‐user
Engineering Objectives

18. always, always,
Always Remember …

19. HVAC Engineering Design Considerations
 MAXIMIZE design accuracy & efficiency
 RESIST over‐designing
 PREVENT over‐engineering

20. Engineering Design
Design is an iterative process …… progresses
through different stages
 ARCHITECT
 STRUCTURAL ENGINEER
 HVAC ENGINEER
 PLUMBING ENGINEER
 ELECTRICAL ENGINEER
 LIGHTING DESIGNER
 ELV ENGINEER
 FIRE PROTECTION ENGINEER
 DESIGN/PROJECT MANAGER
 COST MANGER

21. Design Accuracy
* According to BSRIA BG/6 A Design Framework for Building Services 2nd edition
Conventional RIBA Definition Design Accuracy *
Concept Concept Stage C ± 25%
Scheme Design Development Stage D ± 20%
Detailed Technical Design Stage E ± 15%
Tender Documents Production Information Stage F ± 5%

22. Over‐design
How?
 Application of incorrect design criteria (internal/ external criteria)
 Use of static design techniques
 Over‐use of design margins in rudimentary calculations
 Safety margins applied to plant & equipment
Consequences of over‐designed systems
 Occupies additional space and volume
 Loss of leasable/saleable area
 Increased capital cost
 Increased operating cost due to inefficient operation
 Increased utility charges (particularly for district cooling applications)

23. Over‐engineering
 Over‐engineering is not Over‐design.
 Over‐engineering results from over specifying materials,
equipment and installation details.
 Over‐engineering is normally addressed through value
engineering exercise.

24. Initial Cooling Load Estimate
 Initial concept appraisals will be based upon W/m2 unit area.
 Rule of thumb values typically are,
24

25. Design Temperature Criteria
External: 46OC & 33% RH (30OC wet bulb T) Indoor comfort: 24OC & 50% RH

26. Static Building Heat Gains
 Solar
 Radiation
 Convention
 Transmission
 Conduction
 Infiltration
 Internal
 Lights
 Occupants
 Equipment
26

27. Cooling Load Components
External loads
 Solar heat gain through fenestrations (windows)
 Conductive heat gain through fenestrations
 Conductive heat gain through exterior walls and roofs
 Conductive Heat gain through partitions & interior doors
 Heat gain from outdoor air infiltration
Internal loads
 People
 Electric lights
 Equipment
Ventilation load (Outdoor air tempering)
27

28. Heat Gains through Fenestration
28

29. Fenestration types
(Source: GUARDIAN Glass)
29

30. 30
Heat Transfer ‐ Fenestration
Solar Heat Gain Coefficient (SHGC)
• Percentage of solar energy incident on the glass that is
transferred indoors (directly and indirectly)
• Direct heat gain – Solar energy transmitted
• Indirect heat gain – Solar energy absorbed and
reradiated/convected
Shading Coefficient (SC)
• Considers shading and tinting of glass
• SC = SHGC ÷ 0.87 approximately
For monolithic clear 3mm glass, SC=1.00 and SHGC=0.87
Thermal Conductance Value (U) expressed in W/m2.OK
• Heat gained/lost due to the difference between indoor and
outdoor air temperatures

31. Fenestration comparison
31
(Credit: GUARDIAN Glass)

32. 32
Typical case
• Burj Khalifa features more than
174,000 m2 of fenestration
• High thermal performance
glazing
• SHGC ˂ 0.25 (SC ˂ 0.29)
• U‐Value ˂ 2.00 W/m2.OK
(Source: GUARDIAN Glass)

33. 33
External walls exposed to sun

34. Walls
34

35. Heat Gains Conversion into Cooling Load
35

36. Infiltration – Common Air Leakage Paths

37. Driving Mechanisms for Infiltration
 Stack effect ‐ Air density differences due to indoor and outdoor
air temperatures
 Wind pressure
 Building cracks and openings

38. Realistic Infiltration Estimate Method
 Actually occurs at the perimeter façade
 Practical calculation ‐ based on façade area & expected air‐
tightness (Typical facade air‐tightness values 0.6 – 1.4 L/s.m² facade area at 50 Pa)
 In reality, occurs at all times and can be positive or negative
depending on wind conditions; generally an average value is
used
 Can be suppressed to some extent by pressurization of the
building

39. Estimating Infiltration
Maximum Average Air Infiltration rates in Air Changes per hour (AC/h)
CIBSE Guide A –
Table ref.
Building ‘Leaky’ building
Moderately
‘tight’ building
Table 4.15 Office : Air conditioned, 2000–8000m2 0.60 0.20
Table 4.16
Office : Air conditioned HQ‐type building, 4000–
20000 m2 0.65 0.25
Table 4.17 Factories, Warehouses, Halls 0.65 0.25
Table 4.18 Schools 0.70 0.25
Table 4.19 Hospitals and Health Care buildings 0.60 0.25
Table 4.20 Hotels 0.85 0.30
Table 4.21
Dwellings – 1 floor 1.15 0.40
Dwellings – 2 floors 1.00 0.35
Apartments – 1 to 5 floors 1.00 0.50
Apartments – 6 to 10 floors 1.60 0.55

40. 40
Internal Heat Gains
 Electric lights
 People
 Equipment and appliances

41. 41
Internal Heat Gain ‐ Lights

42. 42
Internal Heat Gain ‐ Lights

43. 43
Internal Heat Gain ‐ Lights
 Heat from ceiling‐recessed luminaires has two (2) components
Heat to conditioned space Heat to ceiling plenum

44. 44
Internal Heat Gain ‐ Occupants
 Anticipated simultaneous occupancy – Furniture scheme OR ASHRAE 62.1
 Degree of activity

45. 45
Internal Heat Gain ‐ Equipment
 Estimate heat gains from equipment for anticipated simultaneous
operation.
 ASHRAE Handbook of Fundamentals provides guidance.
35 W/m2
8 W/m2
17 W/m2

46. Final (Dynamic) Cooling Load
 Represent orientation of the building and the way in which the owner will
operate the building.
 Use dynamic energy/ thermal simulation of a 3D model of the building
using proprietary simulation software.
 Undertake modeling as soon as the architectural form has been
substantially developed so that utility loads can be assessed as early as
possible.
 From experience the results of dynamic simulation have reduced the rule of
thumb cooling loads by 30 – 40% and 20 – 25% lower than a static model.
 The reductions are assisted by incorporating the demand controlled fresh
air and energy recovery features into the simulation.
46

47. Dynamic Thermal Model
Un‐rendered 3‐D building models can be imported into simulation software
47

48. Dynamic Thermal Model
o Thermal templates are created and assigned to the room spaces and zones.
o Incorporate internal heat gain data specific to the space.

49. Schedules are created according to room type for all internal gains (occupancy, lighting,
etc.).
Dynamic Thermal Model

50. Dynamic Thermal Model
 Dynamic thermal model utilizes profiles for internal gains
 Peak loads of different zones do not occur at corresponding times
 When considering peak coincidental load, many of the variable peaks do
not occur at corresponding times
 In static load calculations, these variable peaks are summated
0
500
1,000
1,500
2,000
2,500
3,000
Internal gain
(kW)
Solar gain (kW) External
conduction gain
(kW)
Infiltration gain
(kW)
Sensible Cooling
Load (kW)
Total Cooling
Load (kW)
1,723
280 371 259
2,213
2,633
1,253
245 346 244
1,868
2,025
100% Static Model
Profiled Dynamic Model

51. Fresh (Outdoor) Air Management
 Fresh air treatment (tempering) can constitute 30 ‐ 40% of the total
cooling load
 1.0 m³/sec of fresh air = 40 kW / 11.5 TR cooling energy with energy
recovery devices
 1.0 m³/sec of fresh air = 72 kW / 20.5 TR cooling energy without energy
recovery devices
 Fresh air distribution sizing will be based upon 100% zonal requirements
but they will not necessarily occur simultaneously
 To minimize impact on plant capacity & operating cost:
 Use energy recovery devices (Heat wheel, Run‐around‐coil, Heat pipe, etc.)
 Variable volume fresh air distribution system (VFD fans)
 Demand controlled fresh air (Use of CO2 sensors)
 Occupancy profiles for the respective spaces (Timed operation)

52. Design Margins
 Cooling loads ‐ 10% on sensible load; 5% on latent load
 Flows ‐ 5% on calculated value
 Pressure ‐ 10% on calculated value
 Terminal equipment ‐ 5 to 10% over zone cooling load
 On site cooling plant ‐ 10% over coincidental cooling load
 District cooling service ‐ 0% on coincidental cooling load
(even slightly under‐subscribing DC service is in order)

53. 0.90 1.10 1.60 1.40 1.80
District cooling
system
Water cooled
chiller system
Air cooled chiller
system
Air cooled VRF
system
Split AC system
kW/TR
Costs ‐ Cooling Systems
‐
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
District cooling
system
Water cooled chiller
system
Air cooled chiller
system
Air cooled VRF
system
Split AC system
QAR/TR
District cooling system
Water cooled chiller system
Air cooled chiller system
Air cooled VRF system
Split AC system

54. 30‐Year Capital Expenditure

55. 30‐Year Maintenance Expenditure

56. 30‐Year Utility Expenditure

57. 30‐Year Life Cycle Expenditure

58. 58
Design Principles ‐ Recap
o Use correct external and internal design temperatures
o Select right fenestration materials
o Design heat resistant external walls and roof
o Select energy efficient lighting luminaires
o Adopt correct dynamic occupancy & activity levels
o Use established equipment heat gains
o Allow infiltration based on façade area & expected air‐tightness
o Undertake dynamic thermal modeling

59. HVAC Road Map
 Set up statutory regulatory body for design verification
 Integrate and regulate design criteria for all building types
 Establish and benchmark design efficiency and energy use
 Audit designs prior to issuance of building permit

60. Development Processes

61. One‐stop Real Estate Development Service Provider