MSc Sustainable Mega Design Portfolio by Deepak Sadhwani

SUSTAINABLE MEGA BUILDIN G DESIGN BROADGATE TOWER

Aim • •

Phase 1 | Investigate, model, and evaluate the p e r f o r m a n c e o f a c o m p l e x m e g a b u i l d i n g c a s e s t u d y.

design

and

To o l s U s e d 3D Modelling & Rendering

Phase 2 | Investigation into Passive Strategies to meet the energy demands of the tower with an emphasis on the following Operating energy Building form and impact on aspects of performance (ventilation, daylight, solar penetration, etc)

Rhinoceros

Building envelope / fabric

Grasshopper

SketchUp

Lumion

T h e r m a l S i m u l a t i o n s , C F D, D a y l i g h t & C l i m a t e A n a l y s i s

(U-values, thermal bridging, infiltration, etc) Fabric heat loss and gain Embodied energy and building materials Overall sustainability of the building

•

Phase 3 | Integration of ser vice systems to meet the remaining energy demands of tower with an emphasis on the following M e c h a n i c a l Ve n t i l a t i o n Comfort Artificial lighting

Design Builder Software (Also used for Multi-objective optimization)

Ladybug

Honeybee

Climate Consultant

Data processing, Graphics and Postproduction

Heating and Cooling demands Integrati on of Passive and active elements Renewabl e energy systems

Learning Outcomes • •

Developed a critical position to current sustainable design of mega-buildings.

research

and

practice

Incorporated and demonstrated a coherent understanding of interrelated issues in design proposals; climatic and socio-cultural c o n t e x t s , o c c u p a n c y, t h e u s e of m a t e r i a l s , f a ç a d e te c to n i c s , s t r u c t u r e and construction techniques, building services and performance of mega buildings.

Adobe Photoshop

Adobe Indesign

Artificial Lighting

DiaLUX

Microsoft Excel

Microsoft PowerPoint

STRUCTURE + FABRIC PHASE 2 | BROADGATE TOWER FORM FINDING TO REDUCE PRIMARY ENERGY

Literature review

Analysis of 4 Basic Forms

Optimized forms and WWR

Research Objective : Built Form The aim of the research is to derive a building envelope which acts as a climate modifier by maximizing benefits of solar heat gains, reducing heat losses associated with uncontrolled air infiltration and thermal transmittance of thermal envelope.

Base Form Parallelogram

As per CIBSE Guide A (2015), • minimum window sizes are set to 30% of main façade area. • 40% WWR as benchmark for energy efficiency • 95% to test forms for maximum daylight.

Test Form 1 Rectangle

Test Form 2 Capsule

Constraints • Saint Paul’s view corridor • Raft Foundation Limits • Orientation • Gross Building Area = ~46,500 sqm

Test Form 3 Ellipse

Raft Foundation Limits`

Methodology Multiple EnergyPlus simulation will be applied on the following to predict the building performance in terms of primary energy. Fabric specifications Occupant activities Equipment loads Lighting loads

30% WWR Fixed Windows

Shape WWR Window Type Shading Devices

WWR testing on each orientation

SHAPE OPTIMIZATION

WWR Selection

OPTIMIZED WWR

Fabric Strategy

Internal heat gains Strategy

Morphology

Overhang

Heat gains & heat loss assessment

Test different heights

Louvres Adjust activities

Test for breaks

Best Shading options

Optimized fabric

Optimized internal heat gains

Optimized Morphology

OPTIMIZED PRIMARY ENERGY OPTIONS

426 kWh/ m2

436 kWh/ m2

451 kWh/ m2

441 kWh/ m2

440 kWh/ m2

432 kWh/ m2

501 kWh/ m2

483 kWh/ m2

482 kWh/ m2

484 kWh/ m2

95% WWR Horizontal Strip

Hybrid

Change fabric specifications

426 kWh/ m2

40% WWR Horizontal Strip

Shading Strategy

434 kWh/ m2

Inference • • •

Capsule & Rectangle forms with 30% WWR consumes least primary energy. Ellipse form with 30% WWR consumes 2% more energy. Rectangle form achieves Gross floor area in 33 floors as opposed to 35 floors.

Figure 1. WWR and form simulation results. © Author

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STRUCTURE + FABRIC WWR & WINDOW T YPE OPTIMIZATION WWR testing on each orientation

•

Rectangular form has been assessed for further optimizations because of low primary energy and least height.

•

WWR Parameter on the targeted orientation is changed with rest of the other orientations at 30% WWR and no shading to understand the impact.

50%

30%

70%

40%

Window Type

Deeper windows can ventilate better

Avoid draughts at working level

Consider operable opening lights

Figure 4 from CIBSE Guide F (2012) suggests that window types play a role in reducing heat losses through external air infiltration. A simulation is performed on three different window types to assess the impact on primary energy.

Figure 4. Effect of window shape on ventilation performance. Source: CIBSE Guide F. (2012)

Figure 2. Window Wall ratio selection for each façade. © Author

East

Miscellaneous

Primary Energy Based on WWR

West

Type A Fixed windows Horizontally placed at equal intervals

Type B Continuous windows Horizontally ribbon

Type C Fixed width and height Vertical windows placed at equal intervals

South

Figure 5. Window types selected for simulation. Source: Author Primary Energy (kWh/m2/yr)

Inference

North

The window type with fixed width and height performs the best by reducing heat losses through air ventilation.

30% Primary Energy (kWh/m2/yr)

However, this may result in draughts.

Figure 3. Graph showing impact of WWR on primary energy. © Author

Inference

• WWR 30% on all facades performs the best in terms of primary energy. • WWR has a direct incremental relationship with primary energy. • Primary energy increases with increase in WWR on any façade.

Further study will investigate the shading aspect of the façade system.

Type A

Type B

Type C

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SHADING OPTIMIZATION Adding to the previous research, provision can be made to limit excessive solar gains and thereby, control the rise in internal temperature. This can be done by solar protection through shading. (Approved Document L1A. 2006) This investigation is done in three parts. In each, the parameter on the targeted orientation is changed, and the rest of the façade are in the previous simulation result. 1. Test fixed solar shading devices 6 shading devices have been shortlisted from CIBSE Guide F (2012) and Design Builder shading models to assess the impact on primary energy. 2. Test reveal depth of windows 0.5M and 1M reveal depths are tested on each façade.

1. Fixed Shading Devices Selection

Overhang 0.5M, 1M, 1.5M, 2M

Vertical Louvres 0.5M, 1M, 1.5M, 2M

Overhang + Side fins 0.5M, 1M

Horizontal Louvres 0.5M, 1M, 1.5M, 2M

Horizontal Louvres Overhang + Side fins 0.5M, 1M,

Vertical Louvres Overhang + Side fins 0.5M, 1M,

primary Energy (kWh/m2/yr)

Figure 7. Fixed shading devices and depths. Source: Author

3. Test movable shading devices Shutters and vertical movable louvres can allow the user or BMS to alter the WWR to achieve the desired solar gain. Both operate in a similar pattern. So, shutters have been simulated to assess if there is any further reduction in primary energy from the previous stage.

•

Movable windows reduce the primary energy. However, these can be utilized better after understanding the overall performance of each element of the thermal envelope.

Orientation

2. Reveal windows Figure 5.1 on external shading devices (CIBSE Guide F. 2012) suggests the use of reveal windows.

Reveal windows with varying depths was tested on South, West and East façade, where there may be a significant impact of the solar gains.

Fixed shading devices highlighted in green in Table 1 will be applied for further optimizations Reveal windows of 0.5M depth on West façade works in favor of reducing primary energy.

primary Energy (kWh/m2/yr)

Figure 8. Fixed shading devices simulation analysis on all facades. Source: Author

Table 1. Best performing shading devices. Source: Author

Inference

•

primary Energy (kWh/m2/yr)

The simulations revealed the following results

Best device

Other Performing devices

East

1M Overhang

1M Overhang + Vertical Louvre + Side fin

West

1M horizontal louvre + overhang + side fin

0.5M horizontal louvre + overhang + side fin

1.5M Horizontal louvre

1M Horizontal louvre

South

1M & 0.5M Overhang + Side fin

.5M horizontal louvre + overhang + side fin

2M Overhang

1M Overhang

1M Horizontal louvre

0.5M horizontal louvre + overhang + side fin

2M Overhang

1.5M Horizontal louvre

North

Vertical Louvres

0.5M horizontal louvre + overhang + side fin

2M Overhang

1M Overhang + Side fins

1M horizontal louvre + overhang + side fins

3. Movable Shading Devices Figure 9. Reveal windows. Source: CIBSE Guide F (2012

Primary Energy (kWh/m2/yr)

Movable shutters were tested on East, West and South façade.

No impact of the reveal depth on any façade. West façade showed lower primary energy than the previous simulation with fixed shading devices. Figure 10. Reveal windows simulation results. Source: Author

Figure 11. Movable devices. Source: CIBSE Guide F (2012

The simulation showed that primary energy can be reduced when movable devices are applied on all three façade to minimize solar heat gain in summer months.

Primary Energy (kWh/m2/yr)

Figure 12. Movable devices simulation result. Source: Author

STRUCTURE + FABRIC

Triple Glazing – Electrochromic glass

Heat transmission elaborates on all influential factors impacting the primary energy associated with the tower under different climatic conditions. Building envelope, occupancy schedules, and power densities of lighting and equipment can be optimized to reduce the energy demand.

Smart windows have already been researched for some decades and have a broad market presence. These windows can manipulate g value and transmittance properties according to outside and indoor thermal environment. Thereby, reducing energy costs related to cooling and heating. These can be divided in three categories: (thermos-, photo-, and electro-) chromic materials. A study found that electrochromic are the better performing of the three. (Baitens et al. 2010)

Walls

g value = 0.5

O P T I M I Z ATI ON S

Number of layers – 05

U value = 0.10 W/(m2K)

Frame U value =

Total Thickness = 475mm 25mm

40mm

Vertical Timber cladding

Battens & Counter Battens

U value = 0.35 W/(m2K)

0.63 W/(m2K)

(Passivhaus certified Denmark. 2022)

Target Illuminance = 300 to 500 lux Lighting Power Density CIBSE Guide A 8W/m2 at 300 lux Equates to 2.67W/m2 at 100 lux

100mm

Cross Laminated Timber

Table 3. Occupancy density calculation. Source: Author

The triple glazed electrochromic glass has no impact on Visible Light Transmission. (Baitens et al. 2010)

Space requirements

Figure 15. External Wall specifications. Source: Author

Number of layers – 03 Outside

U value = 0.10 W/(m2K) Total depth = 340mm 2.5mm

Marmoleum finish

140mm

Cross Laminated Timber

Number of layers – 05 Outside

Total depth = 400mm 2.5mm

Thermoplastic Polyolefin (TPO) membrane

60mm x 2 Cork 120mm

Wood Fiber Insulation Hygro membrane

140/150mm

Inside Figure 17. Floor Specification. Source: Author

Laminated Timber Roof Panel

4.2 W/(m2K)

Table 4. Equipment Power density calculation. Source: Author

Equipment type

U value = 0.15 W/(m2K)

Yes Occupancy type – 12:00 Cellular + open plan office. 13:00

Figure 18. Triple Glazing Electrochromic glass. Source: Iqglass UK 2022

Inside

Internal Floor

108

End time

Equipment gains

Figure 16. Roof Specification. Source: Author

No. of people

Start time

Wood Fiber Insulation Timber battens

1,400 sqm

Reduced occupancy at lunchtime?

5 x laminated panels

200mm

Floorplate area

0.077 people/ sqm The occupancy density and patterns Usage diversity (weekday) 75% will have a significant impact 15% on Usage diversity (weekend) the building energy Standard arrival time 09:00 use. (CIBSE TM 54. 2022) Extended arrival time 08:00 Therefore, the Standard departure time 17:00 following data has been set to realize Extended departure times 19:00 how the building will % of computers switched off at the end of the day be used. 60%

Outside

Roof

13.0 sqm/ person

(BCO. 2014)

Occupancy density

3 x laminated panels

Inside

08:00 to 18:00 Monday to Friday

Occupant Schedule

Breather membrane Wood Fiber Insulation

Lighting Control Continuous/ Off Control: Lights switch off completely when minimum dimming point is reached.

Luminaire Type Return-air ducted type with shielding Convective factor = 0.10

IGU Cross-section: Triple Pane

320mm

08:00 to 18:00 Monday to Friday

Lighting gains

Computers High-end desktops Low-end desktops Laptops Screens 19" LCD screen 21" LCD screen Printers and copiers Photocopier Plotter Catering Fridge Coffee Machine

Power Density (W/m2)

Quantities Absolute

Power draw (W) Low On Off active (average)

Usage profiles (% time) Strict Extended Transient hours hours

15 14% 17 16% 77 70%

1 1 1

80 30 20

150 40 30

15% 10% 30%

30% 70% 30%

30% 10% 40%

92 85% 16 15%

0 0

1 1

25 45

20% 20%

50% 50%

30% 30%

2 2

50% 50%

30 120

220 170

0% 0%

100% 100%

1 1

50% 50%

0 25

100 25

120 350

0% 0%

Always On

Total Power draw (W)

25% 1613 Density Variation 10% 607 Full Capacity 08:00 0% to 18:00 Monday1327 to Friday 0% 1175 Holidays per year = 0% 06 days (UK Public 369 Holidays) 0% 60 0% 240 100% 100%

120 350 5860

4.2

Walls

Ceiling

Ventilation

Lighting

Equipment

Occupant

3 2 1 0 -1

3 2 1 0 -1 -2

Heat Balance ( kWh/m2/yr)

3 2 1 0 -1 -2

January

February

2 1 0 -1 -2

March

April 5

2 1

0 -1 -2

3 2 1

0 -1 -2

May

3 2 1

0 -1 -2

June

Heat Balance ( kWh/m2/yr)

3 2 1

0 -1 -2

July

2 1 0 -1

-2

3 2 1 0 -1

-2

Heat Balance ( kWh/m2/yr)

3 2 1 0 -1

-2

September

Solar

Heat Balance ( kWh/m2/yr)

Roof

-2

Heat Balance ( kWh/m2/yr)

Floor

Heat Balance ( kWh/m2/yr)

STRUCTURE + FABRIC HEAT BAL ANCE

October

August

3 2 1 0 -1

-2

November

December Figure 13. Heat Balance Graphs – All months. Source: EnergyPlus

Lighting, Equipment and Occupant heat gains stay high and fluctuate with the number of days in the month.

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Months

January and December February and November

Heat Loss

Very High

Walls Ventilation

Very High

Walls Ventilation

March and October

Very High

April

Very High

May to September

Low

Heat Gains

Low Average

Walls Ventilation

High

Walls Ventilation

Very High

Walls Ventilation

Annual heat Balance

Solar Solar Solar Solar

Heat Balance ( kWh/m2)

Observations

Table 2. Heat Balance Observations – All months. Source: Author

Solar

Walls, Floors, Ceilings,

→

Reduce U value

Ventilation

→

Reduce Infiltration rate, Set Schedule

Lighting, Equipment

→

Reduce Power density, Set Schedule

Occupancy

→

Set Schedule

Solar gain

→

Optimize g value Optimize Solar shading

0 -20 -40

Very High

Inference Optimizations

-60 Figure 14. Heat Balance Graph – Annual. Source: EnergyPlus

136 62 16 19.2

kWh/m2 kWh/m2 kWh/m2 kWh/m2

The optimizations provide high level of occupant comfort using very little energy for heating and cooling.

8.52 tonnes CO2 e Low carbon footprint as compared to existing tower footprint. Due to primary material being CLT.

kWh/m2

800mm

75.37 tonnes CO2 e Extensive double glazing and SS cladding contributes to majority of footprint

2000mm

EMBODIED CARBON

= = = =

3400mm

S U S TA I N AB I L I T Y

Primary energy Operational energy Space heating Space cooling

4800mm

STRUCTURE + FABRIC

Façade Strategy

ENERGY SUMMARY

(a) East, North & South Facade

Units: Tonne CO2e

Figure 19. Embodied Carbon Comparison graphs. Source: Environment Agency

SUSTAINABILITY SUMMARY

Energy & Carbon These optimizations have resulted in 75% energy and 90% carbon reductions. Reduction Achieved through external shading, occupancy sensors, and energy efficient LED lamps

Figure 20. Primary Energy Optimization journey. Source: Author

Operational energy (Figure 21) has been optimized to 75% of its original load. Major impact has been observed for Scheduling, Internal and solar gains. Testing out multiple iterations in WWR and Shading has deep impact as well.

Livability & Well being Smart efficient spaces have been proposed for the tower through use of sensors. Designed with user as the focal point. Gender Positive Occupancy density has been calculated by assuming gender positive office in favor of its female employees.

Reveal depth

kWh/m2

(b) West Facade

75% Reduction

Ecology Reveal Depth windows on the West façade feature planter boxes to capture carbon, purify the air and regenerate the environment. Materials & Sources Materials with low or zero carbon have been selected with aim of making the tower zero carbon.

500mm

Base case

Optimized

Figure 22. Façade Strategy – (a) East, North and South Facade,, (b) West Façade. © Source: Author

References [1] 2015. CIBSE Guide A - Environmental Design (7th Edition). CIBSE. [2] 2012. CIBSE Guide F - Energy Efficiency in Buildings (3rd Edition). CIBSE. [3] Baetens, R., Jelle, B. and Gustavsen, A., 2010. Properties, requirements and possibilities of smart windows for dynamic daylight and solar energy control in buildings: A state-of-the-art review. Solar Energy Materials and Solar Cells, 94(2), pp.87-105.

Figure 21. Operational Energy Optimization. Source: Author

Further Research & Limitations - The tower has been designed considering the whole floorplate as occupied area. However, in practice, service core may consume at most 25% of the floorplate and impact in the heat transfer throughout the tower. -

A further expansion on service core impact is recommended.

HVAC sizing can be simulated to achieve efficient system loads.

A study on renewable technologies that can be applied to the tower may result in the potential of the project being net positive on energy.

[4] Baldinelli, G., Lechowska, A., Bianchi, F. and Schnotale, J., 2020. Sensitivity Analysis of Window Frame Components Effect on Thermal Transmittance. Energies, 13(11), p.2957. [5] Capeluto, I. and Ochoa, C., 2014. Simulation-based method to determine climatic energy strategies of an adaptable building retrofit façade system. Energy, 76, pp.375-384. [6] Cheshire, D. and Menezes, A., 2013. Evaluating

operational energy performance of buildings at the design stage. London: Chartered Institution of Building Services Engineers.

[7] Méndez Echenagucia, T., Capozzoli, A., Cascone, Y. and Sassone, M., 2015. The early design stage of a building envelope: Multi-objective search through heating, cooling and lighting energy performance analysis. Applied Energy, 154, pp.577-591.

Bibliography [8] Iqglassuk.com. 2022. Electro Chromic glass Product data. [online] Available at: https://www.iqglassuk.com/products/electrochromicglass/s14978/ [9] Passivhaustrust.org.uk. 2022. What is Passivhaus?. [online] Available at: https://www.passivhaustrust.org.uk/what_is_passivhaus.php

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Figure 23. Architectural Rendering of Fabric optimized Broadgate Tower. Source: Author

SERVICE SYSTEMS

Multi Objective Optimization for Passive Strategies Design objectives Design variables • Minimize primary energy • WWR on all façade • Minimize discomfort hours >30%<80% (ASHRAE Standard 55 -2004) • 12 Shading devices on all facades

I N T R O D U C TI ON Aims

Primary Energy (kWh/m2/yr)

Minimize the use of delivered energy whilst meeting users’ requirement

reduction

Design the most energy efficient service system Objectives

WWR below 40%

01. Conclusion from Phase 2 on design and performance 08:00 to 18:00 Monday to Friday

Occupancy Walls

U value = 0.10 W/(m2K)

Roof

U value = 0.10 W/(m2K)

Internal Floor

U value = 0.15

Triple Glazing – Electrochromic glass

U value = 0.35 W/(m2K)

Table 1: Ventilation rate calculation. © Author

Category I

Data 1400 l/s 3.6 m 5040 m3

Area Floor clear height Volume Occupancy density No. of occupants Airflow per non-adapted person Total design ventilation air flow rate

Phase 2 Form Selection Phase 2 Envelope selection

10 l/s/person

Table 3. Building Occupancy densities

Results from 375 iterations using MOO feature lowest energy consumption by reducing WWR to below 40% on all façades. This increases the discomfort hours. Therefore, optimum solution is considered as one with WWR under 60% with slightly higher energy consumption. Table 3: Phase 2 and Phase 3 comparison. © Author

Orientation

Table B.8 of EN 16798 1:2019.

East

2800 l/s

Input Yes Yes 2.67 W/m2/ 100 lux 18°C 15.5°C 24°C 28°C 25% 75% Quantities

Absolute

West

Table 2: Schedules summary © Author

CIBSE Guide A

North

HVAC system optimization through Heat recovery

Investigate different types of Heat recovery systems

Lighting levels to minimize discomfort hours

Optimization of natural & artificial lighting

30%

1M Overhang

60%

2M Overhang

30%

1M horizontal louvre + overhang + side fin

45%

2M Overhang

Natural ventilation

Investigation into mode ventilation

30%

1M & 0.5M Overhang + Side fin

40%

0.5M Overhang

Renewable Energy systems for energy reduction

Investigate heat pumps

Operational Carbon

50%

1M horizontal louvre + overhang + side fin

Investigate carbon footprints of shortlisted systems

Renewable Energy systems for energy generation

Assess the potential rooftop PV or BIPV

1M Horizontal louvre

30%

Duarte and Cortiços (2022) Duarte and Cortiços (2022)

Power draw (W) Low On Off active (average)

Investigate different types of HVAC systems

Shading

CIBSE Guide F CIBSE Guide F

HVAC System that best suit the climate and floorplan

WWR

CIBSE Guide F CIBSE Guide F

03. Define objectives leading to improved performance

Shading

Author

South

02. Identify aspects that require further investigation

WWR

Source Author

Passive Optimized Shading

Base Case (Phase 2)

2.8 m3/s

Table 4: Computer Power density calculation. Source. (Menezes et al., 2014)

Power Density (W/m2)

Source

10 sqm/ workplace 140

Summary of Activity and schedule inputs

Computers Low-end desktops Laptops Screens 19" LCD screen

Passive optimized solution featuring alterations in glazing ratios and fixed shading system reduce the annual primary energy consumption from 135 to 129.5 kWh/m2. Figure 1: Multi Objective optimization for WWR and Shading devices. © Author

Ventilation rate

Equipment type

Figure 2: Base case vs Passive Optimized case comparison. © Author

W/(m2K)

2.37 W/m2

Lighting gains

Category I Daylight sensors Occupancy sensors Lighting Power Density Heating Set point Heating set back Cooling setpoint Cooling setback Humidification Dehumidification

Optimum

Usage profiles (% time) Strict Extended Transient hours hours

Always On

Total Power draw (W)

32 76

30% 70%

1 1

30 20

40 30

10% 30%

70% 30%

10% 40%

10% 0%

1137 1308

108

100%

20%

50%

30%

1382 3822 2.7 W/m2

04. Suggest most energy efficient service system

• • •

Room heating and cooling output design Design ductwork Location of plant/ system 05. Transition to architecture design

mixed

SERVICE SYSTEMS

Thermal Zoning Simulations Thermal zones must be defined based on similar internal load densities , occupancy, lighting, thermal and space temperature schedules, etc. (ASHRARE 90.1 2010)

INTERIOR ZONE

10 M

INTERIOR ZONE

TEST 5

4. Low Solar zone Defined along the North side of the tower.

HIGH SOLAR ZONE

TEST 6

2. Interior zone Designed for lights and occupants. May also handle heating systems.

80 M

PERIMETER ZONE – 6M WIDE

PERIMETER ZONE – 5M WIDE

TEST 2

3. High Solar zone Designed to assess the solar loads generated along East to South to West Axis.

HIGH SOLAR ZONE

LOW SOLAR ZONE 40M

PERIMETER ZONE – 4M WIDE

TEST 3

1. Perimeter zone Designed to offset only “skin loads”, that result from energy transfer through the building envelope. Designed for heating only

20 M

Floorplate area = 1600 sqm

TEST 4

TEST 1

H VAC S YS T E M S E L E C T I ON

12 M

INTERIOR ZONE

LOW SOLAR ZONE 30M

Figure 3: All Thermal zone simulations diagrams. © Author

Table 5: HVAC Systems Comparison. Source: Cardiff University. 2022)

Index

System Type

Control

Noise level

Air Distribution

Energy Efficiency

CO2 emissions (kgm3/yr)

Maintenance cost

Plant Room

Occupant area

Ducting

Chilled Ceilings

Good

None

Depends whether active or passive

Very good

No data

Low

None

Separate ducting

Chilled Beam

Good

None

Depends whether active or passive

Very good

No data

Low to average

Low

None

Separate ducting

Constant Volume

Good but limited

Low

Very good

Good to average

No data

Low to average

High

None

High

Fan Coil Units

Good

Can be high

Fair to good

Average

High

Low

None or moderate

Moderate

Variable Air Volume

Good but complex

Low

Very good

Average to high

High

None

High

Variable Refrigerant flow

Good

Can be high

Fair

Good to average

Average to high

Low

None or moderate

None

CAV, Electric Heating

Good

Low

Very good

No data

Average to high

High

None

High

TEST 1 – FULL FLOOR PLATE

TEST 2– 5M WIDE PERIMETER ZONE Floorplate area = 1600 sqm

20M 80M

Same HVAC system proposed for full floorplate

PERIMETER ZONE – 5M WIDE

10M

Ventilation rate = 2.8 m3/s

INTERIOR ZONE

Heat recovery = 85%

Figure 4: Full Floor plate thermal zone © Author

Figure 6: 5M wide periphery thermal zone © Author

Inference

Primary Energy (kWh/m2/yr)

Chilled Ceiling, Chilled beams and VAV systems perform the best in terms of primary energy with 118.4 kWh/m2/yr.

Primary Energy (kWh/m2/yr)

Fan coil unit and VRF have been eliminated from further evaluation due to:

Figure 5: Comparison of Test 1 systems © Author

Base Case

High energy demand High noise levels Fair air distribution High maintenance cost

Figure 7: Comparison of Test 2 systems. © Author

Inference Energy Performance of all the systems fall in the range of 118119 kWh/m2/yr with the best ones as follows: - Chilled Ceilings + Constant volume - Chilled Beam + Chilled ceiling - Constant volume + VAV

SERVICE SYSTEMS

H VAC S YS T E M S E L E C T I ON Index

System Type

Table 6: HVAC Systems Comparison. Source: Cardiff University. 2022)

Control

Noise level

Air Distribution

Energy Efficiency

CO2 emissions (kgm3/yr)

Maintenance cost

Plant Room

Occupant area

Ducting

Chilled Ceilings

Good

None

Depends whether active or passive

Very good

No data

Low

None

Separate ducting

Chilled Beam

Good

None

Depends whether active or passive

Very good

No data

Low to average

Low

None

Separate ducting

Constant Volume

Good but limited

Low

Very good

Good to average

No data

Low to average

High

None

High

Variable Air Volume

Good but complex

Low

Very good

Average to high

High

None

High

CAV, Electric Heating

Good

Low

Very good

No data

Average to high

High

None

High

Inference

TEST 3 – 4M WIDE PERIMETER ZONE

Energy Performance reduces with shorter perimeter depth.

PERIMETER ZONE – 4M WIDE 12M

INTERIOR ZONE

6M Periphery shows 12 options with same energy as the result of Test 1. Operational Carbon study will identify the best possible outcome of these.

PERIMETER ZONE – 6M WIDE

The best-case energy use stays at 118 kWh/m2/yr

Figure 8: 4M wide periphery thermal zone © Author

Inference

TEST 4 – 6M WIDE PERIMETER ZONE

INTERIOR ZONE

Primary Energy (kWh/m2/yr)

Inference

TEST 5 – SOLAR GAIN ZONE | EQUAL

HIGH SOLAR ZONE

LOW SOLAR ZONE 40M

Primary Energy (kWh/m2/yr)

TEST 6 – SOLAR GAIN ZONE | 2/3 – 1/3

There is a considerable drop in primary energy performance from 118 to 106 kWh/m2/yr. Constant Volume systems show a slight increase in primary energy in either of the zones

HIGH SOLAR ZONE

Inference

LOW SOLAR ZONE 30M

Zone division in favor of Sun path does not reduce the primary energy demand of the tower. The same is observed when the zone depths are reversed. The lowest primary energy stays at 106 kWh/m2/yr Best performing systems A B D

Chilled Ceilings Chilled Beams VAV

A combination of either of the three with Test Zone 5 results in the best energy performance of the tower.

SERVICE SYSTEMS

O P E R AT I O N A L C A R B O N E M I S S I O N | M U LT I O B J E C T I V E O P T I M I Z AT I O N

V E N T I L AT I O N S T R AT EG Y, H E AT P U M P S

OPTIMIZATION OBJECTIVE

NATURAL VENTILATION | MIXED MODE

DESIGN VARIABLES

Indoor minimum temperature control set to 24C in both zones.

MINIMIZE TOTAL SITE ENERGY (kWh) 20 HVAC Systems

Primary Energy (kWh/m2/yr)

Table 13.5 Ventilation based on air change rates of BSRIA states that office above ground require 2 to 6 air changes per hour. These air change rates are tested for both, natural ventilation and mixed mode systems.

Mixed mode ventilation with 5 ac/h shows a drop from 106 to 100 kWh/m2/yr Primary Energy.

Chilled Ceiling

Chilled Beams

Air cooled chiller

Air Cooled Chiller, DOAS

Free Cooling Ground HX

DOAS, Displacement Ventilation

VAV Air Cooled Chiller

Ground Source (GSHP)

Hybrid with Gas boiler

Unitary Waterto-air

Convectors

Water to Water: Heated floors

Zone Waterto-air

Water to Water: Heated floors, chilled beams

Air cooled chiller

Air-side HR, OAR

OAR

Steam humidifier, Airside HR, OAR

Water cooled chiller

Full humidity control

HR, OAR

HR, OAR + Mixed mode

Ground Source (GSHP)

Hybrid with Gas boiler

Unitary Water-to-air

Convectors

Water to Water: Heated floors

Zone Water-to-air

Water to Water: Heated floors, chilled beams

Category I

Heating Set point Heating set back Cooling setpoint Cooling setback

Previous Input

Final Input

20°C 16°C 22°C 25°C

18°C 15.5°C 24°C 28°C

Ground Source Heat pumps has been identified as the best performing HVAC system with annual primary energy of 78.4 kWh/sqm and 323,400 kgCO2e operational carbon emissions in 33 office floors.

Combination of ASHP and GSHP

• Water to water based • Heated floor • Mixed mode ventilation of 5 air changes per hour

Combination of ASHP and GSHP with VAV systems

Combination of ASHP and GSHP with Active systems

GSHP Water to Water heat Pump, Heated Floor, Nat Vent

GSHP Water to Water heat Pump, Heated Floor, Chilled Beams, Nat Vent

GSHP Water to Water heat Pump, Heated Floor, Nat Vent

GSHP Water to Water heat Pump, Heated Floor, Chilled Beams, Nat Vent

GSHP Water to Water heat Pump, Heated Floor, Nat Vent

Air to Water Heat Pump (ASHP), Convectors, Nat Vent

• This rate of ventilation can be achieved by cross ventilation. Wind drives air through open windows on the windward side of the building (West) and open windows on opposite side (East) to allow stale air to escape.

Primary Energy (kWh/m2/yr)

West Facade

• Occupants have the flexibility to manually operate the windows. • Heated floors in zones with high occupancy.

East Facade

20 M

South Zone

Chilled Beam system

North Zone

Combination of Chilled systems with VAV systems

Lowest GSHP, Water to HR - HeatNatural recovery Water, OAR - ventilation Outdoor Air Reset in both Zones

Lowest GSHP, Water to Water, Natural ventilation in both Zones

Air Source (ASHP)

Iteration

VAV Water Cooled Chiller

Reheat

Summary of Activity and schedule inputs

RENEWABLE ENERGY SOURCES | HEAT PUMPS

VAV Dual Duct

Fan Assisted Reheat

Table 7: Heat Pumps Comparison. Source: Design Builder. 2022

Index

MINIMIZE OPERATIONAL CARBON EMISSIONS (kgCO2e)

SERVICE SYSTEMS

T E C H N O LOG I C AL I N N O VAT I O N S

RENEWABLE ENERGY SOURCES | GENERATION | SOLAR PANELS

Heat balance Annual Summary Change in the lighting power density resulted in 10% primary energy demand reduction from 78.4 kWh to 66.2 kWh. A final set of passive design alterations include using Electrochromic glass to control the g value of the tower based on outside conditions. g values of 0.3 to 0.9 are tested by identifying months and ultimately, movable shades are used to optimize the WWR during the summer months.

Target Energy generation = 52 kWh/(m2/yr) x 33 floors x 1400 m2 = 2.4 million kWh/year

Area required per kWp system

7 sqm

System Loss

10%

Electricity generated (kWh)

Primary Energy (kWh/m2/yr)

Electricity generated (kWh)

Balanced Jan

Feb

Moderate to High Solar gains Mar

Apr

May

Jun

Jul

Optimal Aug

Sep

Oct

Nov

Dec

Slope

Figure 25: PV Slope comparison © European Commission. 2022 Table 12: Monthly breakdown for g value alterations and movable shading.

Months

Heat Loss

January and December

Moderate

Floor, Roof

February and November

Moderate

Floor, Roof

March and October

Moderate

Floor, Roof

April

Low

Floor, Roof

May to September

Low

Floor, Roof

Insulation Add 100mm wood fiber insulation Floor U Value = 0.12 W/(m2K) Roof U Value = 0.07 W/(m2K)

Heat Gains

Movable Shading

g value

Low

Solar

0.9

Low

Solar

0.7

Moderate

Solar

0.6

High

Solar

Yes

0.4

Very High

Solar

Yes

0.3

Primary Energy (kWh/m2/yr)

The infiltration rate has been changed from 0.6 ac/h to 0.2 ac/h assuming a very high-quality construction. These optimizations result in a primary energy reduction from 66.21 kWh/sqm/year to 52 kWh/sqm/year.

-61%

The annual primary energy demand has been reduced from 135 kWh/ sqm to 46 kWh/m2 considering the potential energy generated through rooftop PV. This has been achieved by using Ground source heat pumps as primary service system for the tower.

Figure 27: Rooftop and BIPV Option

Figure 28: Slope built form option

Option A

Option B

Roof Area

1400 sqm = 200 kWp

Wall Area

600 sqm = 85 kWp

Potential Energy generation Reduction Final Primary Energy

~290,000 kWh ~10% 46.1 kWh/m2

Roof Area

Potential Energy generation Reduction Final Primary Energy

2000 sqm = 285 kWp

~248,000 kWh ~9% 46.8 kWh/m2

SERVICE SYSTEMS

S YS T E M I M P L E M EN TAT I O N

T E C H N O LOG I C AL I N N O VAT I O N S

HVAC loads are calculated for the middle floor to investigate the reduction of system loads

ARTIFICIAL LIGHTING STRATEGY

Parameter Product Lamp Power

Conference

Office workspaces

Reception

Conference

Breakout

GLAMOX C95S240X1500 LED 4500 830 OP

GLAMOX C90 – R625x625 LED 2200 830 MP

COOPER HCC8S15D010MBHM8152092781MDHWF

MEDO 30 1001905 SLV

30W

15W

13.9W

12.1W

4198 lumens

1962 lumens

1103 lumens

1498 lumens

140 lumens/W

131 lumens/W

79 lumens/W

124 lumens/W

No. of lamps

PIR Sensor

Yes

Total flux Luminous efficacy

Floor

Roof Heat Balance ( kWh/m2)

Breakout

Ceiling

200 100 0 -100 -200

Heat Balance ( kWh/m2)

Private Office

Heat Balance ( kWh/m2)

ELE ROOM

Heat Balance ( kWh/m2)

A zonal lighting analysis is used to calculate the actual power density using energy efficient LED fixtured to achieve illuminance of 500 lux as per CIBSE Guide A

Walls

200 100 0 -100 -200

Ventilation

Lighting

100 0 -100 -200

Primary Supply Secondary Supply 1 Secondary Supply 2 Secondary Supply 3 Outlet duct 1 Outlet duct 2 Outlet duct 3 Outlet duct 4 Extract

Solar

Heating

100 0

Plant

-100

GSHP System size Total design capacity = ~300 kW per floor

-200

Table 13: Duct sizing & fan power calculation.

Flow Rate Air Velocity

Circular Duct Diameter

m3/s

m/s

12 29 36 29 1 1 4 4

1.05 0.44 0.875 0.875 0.0375 0.0375 0.1575 0.1575

6 4 5 5 2 2 3 3

450 350 450 450 150 150 250 250

0.945

Mixed mode Ventilation System

Rectangular Duct width (mm)

height (mm)

500 x 550 x 500 x 500 x 150 x 150 x 300 x 300 x Total Pressure

Pressure Total pressure drop Drop

350 200 350 350 125 125 175 175 on the fan

0.8 0.38 0.5 0.5 0.2 0.2 0.3 0.3

9.6 11.02 18 14.5 0.2 0.2 1.2 1.2 55.92

50% allowance for grilles

27.96

Grand total for system

83.88

Plant Level 2 Basement GSHP

Figure 30: Location of services. © Author Legend Primary Supply duct Secondary Supply duct Outlet Supply duct Return Air Primary duct Return Air Primary duct

• Outside air is used in summer months when conditions are favorable.

Exhaust grille

Return Air Primary

AHU

Primary supply

Return Air Primary

Supply diffuser

Return Air Primary

Cooling

Heat recovery

Space cooling Base case = 19.2 kWh/m2 Final case = 8.7 kWh/m2 Design capacity = 130 kW

200

Duct sizing & Fan Power Section

Occupant

Space heating Base case = 16 kWh/m2 Final case = 12 kWh/m2 Design capacity = 168 kW

200

Duct Length

Equipment

Secondary supply 1

Secondary supply 3

Under Floor Heating and Cooling System

• Radiant heating and cooling through the GSHP is provided in open plan space (high occupancy) • Low occupancy spaces (private offices, meeting rooms, etc) are ventilated from the top. • Convectors are proposed on the periphery to avoid draughts

Legend Radiant heating Convectors

Reception

Conference

Private Office Working plane Targeted lux Calculated lux Lighting Power density

Open plan office

Break-out space

750 mm

AHU

500 650 lux

SERVICE SYSTEMS

TRANSITION TO ARCHITECTURE DESIGN

S YS T E M I M P L E M EN TAT I O N

The Base form has been designed as a fully glazed timber tower with CLT Panels for flooring and wall. Vertical shading has been designed towards the North and South façade.

A curved Double Skin façade wrapping East and West façade is introduced to capture natural ventilation during favorable conditions, mitigating horizontal and vertical wind loads.

Perforations are introduced in the exterior skin to capture natural daylight and wind

Openings are optimized based on the required WWR, to maximize daylight and reduce overall primary energy. Figure 34: Architectural rendering of the tower. © Author Figure 33. Architectural transition diagrams. © Author