Aero Hive, designed by Midori Architects, aims to challenge the common belief that contemporary tall buildings cannot be ventilated naturally due to their height and serves as a model of sustainability

A Breathing Entity

Figure 1: Aero Hive – A beacon of Sustainability (©Suraksha Acharya, Midori Architects)

The building offers pause from the typical hermetically

sealed glass-boxes. Key to these forms of adaptation is

the relationship of the building to its environment and

the contextual forces that shape the form development and its

environmental behavior.

The wind flow to the indoor spaces is carried using wind-

scooping and the ‘venturi’ effect through the traversing

green diaphragms that are oriented facing prevailing winds.

Aerodynamic architectural design is realized by taking into

consideration building orientation, position, form, and plan

variations. An algorithmic process of designing has been

followed by creating a differentiated array of hexagonal floor

plates that variably changes scale based on environmental

criteria, functional aspects, structural logics and aesthetic

parameters.

Computational modeling and environmental testing, namely,

solar insolation and CFD analysis were carried out to verify

the climatic effects of twisting geometries. Key to these

forms of adaptation is the relationship of the building to their

environment and the contextual forces that shape the form

development and environmental behavior.

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www.mgsarchitecture.in

MGS - Modern Green Structures & Architecture 13 February 2019

Facade

Emission-free economyThe site is located at Kai Tak area of Kowloon, Hong Kong,

Following the relocation of Hong Kong International Airport

from Kowloon City, this derelict reclaimed area was envisioned

to be redeveloped into a distinguished, vibrant, attractive and

people-oriented sustainable neighborhood.

Taking this vision forward, we have chosen a vacant site at

runway precinct 4C4, measuring approximately 155m x 80m

(i.e.10730sq.m) facing Victoria harbor. To foster a streetscape

Figure 2: Aero Hive – Vertical Diaphragms or ‘Green Lungs’ (©Suraksha Acharya, Midori Architects®)

which is “walkable”, “livable” and “comfortable”, an emission-free

economy is the only way forward. Effective ways to deal with the

‘street canyon’ effect, is to reduce tail-pipe emissions, initiating

an emission free zone to achieve long term cleaner, more

efficient public transport. Availability of private passenger hybrid

and electric vehicles with a wide availability of charging points

will reduce exposure to pollution. As a step further, the emissions

at sea level easily get blown to areas with high population

density, hence, the ships docking at Kai Tak Cruise Terminal will be

required to fuel switch at berth, to a much cleaner 0.5% sulphur.

Aero Hive is a breathing entity; the breath of this building transpires through vertical diaphragms in the form of green sky atriums that behave as lungs, providing natural ventilation, and is the preferred option when attempting to deliver fresh air to any space due to its low energy requirementsAr. Suraksha Acharya

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Figure 3: Aero Hive - Annual Solar Insolation (WattHour)

Figure 4 : Aero Hive –Environmental Analysis of Microclimate (Courtesy: Midori Architects)

Environmental receptivityEnvironmental factors and structural

concepts shape the form and skin of

this tower. For optimum environmental

operating efficiency, the building

form should be accordingly shaped,

maximizing sun control for different

solar angles and insolation intensities.

A series of shading and insolation (Wh)

studies conducted showed that twisting

the tapered hexagonal form 90 degrees

clockwise (north-west quadrant) and

anti-clockwise (south-east quadrant)

yielded self-shading benefits. In addition,

the towers (Tower A & Tower B) are

positioned such that they mutually shade

each other at different times of the day

and year.

By carefully incorporating the natural

wind patterns of the site, the building

is designed to accommodate changing

wind conditions. The three wind scoops

on each tower anxillary and efficiently

capture the moving air into the rotating

Sky Atria – which is then transferred

throughout the floor using large plenums.

Aero Hive uses scooping for air intake

with the help of hexagonal arms that

function as wing walls and allows air

to exit through operable windows or

adjacent Atria. During the day, south

easterly cool sea-breezes provide relief,

and in the evening, cool northerly winds

come down the forested slope and wash

across the building.

In windy climates like Hong Kong with

very directional extreme winds, building

shapes that are directionally sensitive are

more effective than traditionally shaped

buildings. Developments in structural

systems of high-strength materials with

increased height to weight ratio but

reduced stiffness have become greatly

affected by wind. Major structural

and aerodynamic modification in the

design development includes tapering,

sculptured building shape, openings

and twisting of building. In addition,

along with advances in visco-elastic

materials like tuned mass damper as well

as structural systems like diagrid, the

shape of the towers becomes distinctly

modified by the micro-ecology. To drive

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Figure 5: Aero Hive – Floor Plate Morphology (Courtesy: Midori Architects)

Figure 6- Aero Hive – Structure & Exoskeleton (©Suraksha Acharya, Midori Architects®)

the natural currents to enhance air volume exchange, pressure

differentials between windward (up-wind) and leeward

(down-wind) faces of a building were analyzed, using CFD for

thorough ventilation and surface wind flow acceleration.

Parametric differentiation & structural rationalisationA central triangulated core anchors each tower that arises

290m above ground level carrying a twisting form. Form is

encapsulated by a triangulated exoskeleton articulating a

multistorey atrium located at the extremities, leaving clear

floor plates for functional distribution. The triangulated

structure geometry with a base height of 1:4 floors extends

across the façade to form the exoskeleton. The rotational

and scaling aspects of floor plates around the central cores

creates a folding form that grows high to create an amorphous

geometry with atriums that spiral along the towers in two

different directions as per climatic aspects. Two dynamic

looking towers connect at three distinct levels with structural

bridges formed by triangulated trusses that stretch out from

triangulated exoskeleton.

Aerodynamics & computational fluid dynamicsLow values of drag and lift are produced by a hexagonal

cylinder that it is comparable to a circular cylinder cross

section. Wind effects on different geometric shaped buildings

such as circular, square, triangle & hexagon were analyzed

using CFD simulation software. The results showed that the

circular shape had the lowest wind pressure coefficient and the

square had the greatest wind pressure coefficient. To design a

shape which maximizes aerodynamic and packing efficiency,

a unique optimization linking these two critical characteristics

was investigated. While it is known that a sphere will have

the greatest aerodynamic efficiency, its packing efficiency

will result in a huge loss of space. Shapes which can mesh

such as rectangles or irregular shapes which interlock have a

much higher packing efficiency. Having a spectrum of different

shapes in mind, this analysis examined the potential of a

hexagonal shape. It came to be known that an efficiency of

90% can be achieved with hexagonal packing. The intention

was to explore the facilitation of air movement with respect

for the final form, the feasibility of ventilation techniques

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Fact File

Project: Aero Hive

Client: Bee Breeders competition organisers & Manipal University, Dubai

Location: Kai Tak, Hong Kong

Typology: Commercial (mixed use) / competition

Size: 1884717 sq.ft (175096 sq.m)

Architectural Design: Suraksha Acharya, Midori Architects

Visualization: - Vizis, Chennai

Parametric modelling: Rat[LAB]

Material Palette

Aluminium composite cladding, core tube trussed

structure, operable double-glazed triangulated panels

Awards

Aero Hive has been awarded 1st place in the SHYHIVE

Skyscraper Challenge 2018, organized by Bee Breeders

(USA) in association with Manipal Executive Education

(MEE) Dubai, and the renowned Silver A’ Design Award at

Architecture, Building and Structure Design Competition

2018, Como, Italy.

Figure 7: Aero Hive- East CFD Simulation (Courtesy: Midori Architects)

Figure 8: Aero Hive - Façade Development based on environmental factors (Courtesy: Midori Architects)

using atriums that transverse effectively, so as to enhance

wind indoors. Using Simulation CFD, the optimized towers

were modelled as a block, and the Boundary conditions were

set up to emulate the site conditions for 500m radius of urban

fabric. Simulations were run, based on HongKong 10-year

weather data for prevailing directions East (4.1m/s) and South

East (2.5m/s) respectively for 500 iterations.

Facade developmentThe building has been optimized such that sunlight will be

carefully controlled to bring in diffused lighting while avoiding

direct solar heat. Each three-story semi enclosed atrium

contains office spaces on either side of the exterior hexagonal

arms framing the visual communication to the outside and

clusters, bringing people together. The green areas are not

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Facade

Figure 9: Aero Hive – Parametric Facade (©Suraksha Acharya, Midori Architects®)

only recreational with psychological benefits for

employees but also add protection from strong

winds and avoid glare within office spaces. A

communal lobby, ancillary spaces (indoor sports

facilities) and sky park make up the designer’s

proposed function, which will be open to the public.

The three rotating hexagonal atria’s focus on

accelerating airflow through each floor. Hong

Kong’s climate is sub-tropical, but for half the year

it is largely temperate, with the average yearly

temperature at 18 C (64 F) to 25 C (77 F), with

summer mean daytime temperatures touching

32 C (90 F). In winter, strong and cold winds

are generated from the North to Hong Kong; in

summer, the wind reverses in direction and brings

the warm and humid air from the South.

In the workplaces, the double-glazed windows’ skin

opens inwards at the top with an angle of maximum

15°, thus allowing fresh air to move indoors. 30%

of the panels are static and the rest 70% of the

facade panels are kinetic. The percentage of opening

is determined by the amount of ventilation

required for the space based on data obtained

from internal CO2 sensors. When the natural

ventilation strategy cannot be applied due

to extreme weather conditions, mechanical

systems help ventilate the building. Sky gardens

always remain naturally ventilated during

summer. During winters, when temperatures

are uncomfortably low, natural ventilation is

restricted.

Aero Hive’s aerodynamic architectural design

plays a critical role in mitigating the “wall effect”

caused by uniform high-rise developments.

The flared roofline at the architectural top is

designed to accommodate a Sky Park – a public

green observatory that addresses the “urban

heat island” effect island due to the combination

of high-density, tropical climate and high-rise

buildings. This creates a natural habitat, filtering

pollutants and reducing CO2 content in the air

while satisfying the aesthetic needs of a roof.