Hong Kong Institute of Surveyors (HKIS) Young Surveyors Group Technical Seminar

19 May 2014 (Mon) 2014519()

Dr. Sam C. M. HuiDepartment of Mechanical Engineering

The University of Hong KongE-mail: cmhui@hku.hk

Green Roofs and Vertical Greening in Hong Kong

Contents

Introduction Potential benefits Green roof examples Vertical greening examples Major considerations Development trends Conclusions

Introduction

Hong Kong Special Administrative Region (HKSAR) Land area : 1,104 km2 Population : 7.18 millions Population density : 6,504 persons/ km2

High urban density to meet population growth Urban heat island and lack of greenery space

Introduction

Promote green roofs and vertical greening to achieve urban sustainability

Common types of roof greening: podium gardens and sky gardens

New greening techniques: Extensive green roofs Living walls & green facades

A residential podium garden

(Photos taken by Dr Sam C M Hui)

Podium garden (Kowloon Station) ()

(Photos taken by Dr Sam C M Hui)

Sky gardens in commercial buildings

(Kowloon Commerce Centre )

(HSBC Building Mongkok )

Introduction

Our research * Started in 2002 2002

1. Assess the potential & impacts of urban greening

2. Develop practical guidelines & information

3. Evaluate building greening policy

4. Promote education & technology development

(* See also http://me.hku.hk/bse/greenroof/)

Introduction

Examples of previous studies: Energy and environmental performance of green

roofs and living walls

Design and assessment of modular green roof systems

Life cycle analysis of green roof urban farming

Feasibility study of green noise barriers

Green roof research at a construction site office in Hong Kong (2002-2006)

Green site office Modular design

Green site office and typical site office Water sprinkler

Green roof Conventional roof

Infrared pictures:

Green roof research at a construction site office in Hong Kong

Green roof and vertical green for construction site offices

Thermal modelling of green roofs

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Evapo-transpiration:

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Conduction:

Study of modular green roof systems (2007-2008)

Aluminum trays Wooden boxes

Plastic trays Plastic trays (infrared photo)

Dry plant

Wet plant

Green roof systems from Germany (left) and Japan (right)

Vegetation

Growing medium

Filter membrane

Drainage layer

Waterproofing membrane

Support panel

Thermal insulation

Vapour control layer

Structural support

Typical structure of extensive green roof

Green noise barrier

(Source: Highway Department, HK)

Introduction

Recent research studies : Technical guidelines for green roof systems (done)

Integration of green roof and solar energy systems

Evaluate indoor living walls Thermal regulation performance of living walls

Year-round energy performance of vertical greening systems

Hui, S. C. M., 2013. Guidelines for the Design and Application of Green Roof Systems, Chartered Institution of Building Services Engineers, London. (ISBN 978 1 906846 40 4)

1. Introduction 2. Scope 3. Definitions 4. Planning Requirements 5. Design Considerations 6. Construction Methods 7. Maintenance Issues 8. Project Management

Integration of green roof and solar energy systems

(Photos taken by Dr Sam C M Hui)

Indoor green wall

(International Commerce Centre )

(International Finance Centre )

(Photos taken by Dr Sam C M Hui)

Energy balance for a green wall

(Source: Ottel, M., 2011. The Green Building Envelope: Vertical Greening, PhD Thesis, Technical University of Delft, The Netherlands.)

Infra-red photos of vertical greening

Bare wall Living wall

Introduction

Current studies : Technical guidelines for vertical greening systems

Evapotranspiration analysis of vertical greening systems

Double skin faade with vegetation plants

HK green roof and green building policy

Potential benefits

Green roofs & vertical greening Building integrated vegetation Urban cityscape Green infrastructure

Possible benefits: 1. Environmental 2. Economic 3. Social

Potential benefits

1. Environmental benefits: - Mitigate urban heat island - Improve air quality - Stormwater management - Create natural habitat - Increase biodiversity - Insulate and absorb sound - Possible urban farming

(Source: SCMP and Hong Kong Observatory)

Urban heat island in Hong Kong

(Source: www.accuweather.com)

Rainstorm flooding problems in Hong Kong (2008)

Potential benefits

2. Economic benefits: - Improve roof durability - Increase roof material lifetime - Reduce building cooling load and energy costs

- Provide open space & increase property value

- Green building credit points & image

Evapo-transpiration

Shading

Thermal mass

Indoor

Insulating property

Thermal properties of green roofs

Roof slab

Outdoor

Potential benefits

3. Social benefits: - Aesthetic for city space - Provide community green space & gardens for

sports & leisure

- Community participation - Provide education opportunities - Enhance local employment

School education green roof project

(Source: Ng Yuk Secondary School)

School education green roof project

(Source: Environment and Conservation Fund)

Green Roofs

Urban Agriculture

Urban Greenery

Green Building

Sustainability

Food System

City Environment

Social

Environmental

Economic

Green roof examples

Green roof application is growing fast in Hong Kong in recent years 1. Government projects (as demonstration) () (> 250 nos.)

2. School projects (with incentives/subsidies) (/)

3. Private projects (for green image) ()

Examples of green roofs in Hong Kong

HK Wetland Park

EMSD Headquarters Ocean Park

Parklane, TST (Photos taken by Dr Sam C M Hui)

Hong Kong Wetland Park Phases II

(Source: Architectural Services Department)

Greening at Tamar project

(Photos taken by Dr Sam C M Hui)

Green roof

Green wall (to be)

Green roof lawn

New prison: green roof

(Source: ArchSD)

Government green roof projects

(Source: Drainage Services Department and Housing Authority)

Sewage treatment plant Refuge room

Sewage pumping station

Roof greening on covered walkway

(Source: Housing Department, HK)

(Photo taken by Dr Sam C M Hui)

School green roof project

(Source: Architectural Services Department)

School green roof project

(Source: Architectural Services Department)

HKU Centennial Campus

(Photos taken by Dr Sam C M Hui)

Introduce greening on existing rooftops

(Source: Development Bureau, HK)

Green roof farming (Hysan Place, Causeway Bay) ()

(Photos taken by Dr Sam C M Hui)

Vertical greening examples

Common reasons for vertical greening : Aesthetic (how it looks) () Cognitive (meaning) () Experiential (use) () Planning and financial gains ($) Pollution absorption (air) () Ecology (habitats) ()

Vertical greening examples

Application methods of vertical greening : 1. Building faades or outdoor vertical surfaces

2. Interior walls or indoor vertical surfaces

3. Noise barriers (e.g. along the roads)()

4. Slopes

An example of vertical greening

(Source: CityWalk, Tsuen Wan, , www.citywalk.com.hk)

A green wall in Central

A green wall project in Kowloon Bay

(18 Kowloon East)

A green wall project in Wanchai

(The Hennessy)

Green wall for exhibition function

(Source: www.greening.gov.hk)

Government demonstration projects

(Source: www.greening.gov.hk)

For a housing estate

For a government building (EMSD Headquarters)

For a school building

A school green wall project

(Source: www.everplant.com.hk)

An indoor green wall in a hotel

(Source: Hotel ICON)

Indoor green wall

Indoor green wall

(CityWalk 2, Tsuen Wan, 2)

Greening on highway structures

(Source: Highway Department, HK)

Greening on slopes

(Source: Civil Engineering and Development Department)

(Source: Civil Engineering and Development Department)

Major considerations

Key factors for planning Structural loading Accessibility Waterproofing Drainage Maintenance

Other design considerations Selection of plants (e.g. hardy plants) Stakeholders involvement & support

Major considerations

Climatic factors Typhoons: strong wind might blow away the

vegetation and soil Heavy rainfalls: hold and drain the rain water

without creating pools of stagnant standing water

High temperature: affect some plant species

Strong sunlight: solar and UV radiation

Major considerations

High-rise buildings: very limited roof spaces Better to apply green roofs to medium- or low-rise

buildings/structures or podium roofs /

Podium/sky gardens Structural loading

Determine validity and cost For existing buildings

Light-weight greening systems

Green roof on a low-rise building

(Source: Hongkong Electric Co., Ltd.)

Infrared photo for assessing thermal effects

Typical hardy plants (sedums) used for green roofs

Major considerations

Costs and commitments Capital cost (direct & indirect costs)()

Recurrent maintenance costs Life cycle costs Risk of failure costs Maintenance commitments Ownership

Development trends

Sustainable technologies Rainwater harvesting Renewable energy (e.g. solar photovoltaic &

wind)() Composting (for producing fertilizer) ()

Farming & food production Agricultural green roofs Edible living walls

Integration of green roof, rainwater recycling and renewable energy

(Source: www.zinco.de)

Integration of green roof and solar energy systems

Sustainable rooftop farming

(Source: www.skyvegetables.com)

Wind energy

Solar energy

Composting

Rainwater harvesting

Greenhouse

Green roof research with integrated systems Rainwaterrecycling

Micro-windturbines

Modularsystem

Built-insystem

Space for green roof research and urban farming

Urban farming on green roofs

Farming on the roof

Vegetables and herbal plants

Green beans Water melon (Photos taken by Dr Sam C M Hui; Acknowledgement: St. Bonaventure Catholic Primary School )

Edible vertical garden

(Source: www.lifeisagarden.com.au)

Soil-less green roof farming (purple potato) [An elderly home in HK ]

(Photos taken by Dr Sam C M Hui)

Conclusions

Green roofs and vertical greening are developing fast in Hong Kong

New techniques are applied to urban greening

More research is needed to determine suitable technologies and policy for promoting them

THANK YOU !!

(More information: http://me.hku.hk/bse/greenroof/)